Mono No

Outline of Naval Armament and Preparations for War, Part I

145

Outline of Naval Armament and Preparations for War, Part II

149

Outline of Naval Armament and Preparations for War, Part III

160

Outline of Naval Armament and Preparations for War, Part IV

169

Outline of Naval Armament and Preparations for War, Part V

172

Outline of Naval Armament and Preparations for War, Part VI

174

 

Japanese Monograph No. 145

OUTLINE OF NAVAL ARMAMENT AND PREPARATIONS FOR WAR

Part I

PREPARED BY MILITARY HISTORY SECTION HEADQUARTERS, ARMY FORCES FAR EAST

DISTRIBUTED BY OFFICE OF THE CHIEF OF MILITARY HISTORY DEPARTMENT OF THE ARMY

This is the first of a series of six monographs in regard to Japan's naval armament in preparation for and during the Pacific War.

Additional monographs covering Japan's naval armament plans are:

Mono No

Outline of Naval Armament and Preparations for War, Part II

149

Outline of Naval Armament and Preparations for War, Part III

160

Outline of Naval Armament and Preparations for War, Part IV

169

Outline of Naval Armament and Preparations for War, Part V

172

Outline of Naval Armament and Preparations for War, Part VI

174

--iii--

Preface

Through Instructions No. 126 to the Japanese Government, 12 October 1945, subject: Institution for War Records Investigation, steps were initiated to exploit military historical records and official reports of the Japanese War Ministry and Japanese General Staff. Upon dissolution of the War Ministry and the Japanese General Staff, and the transfer of their former functions to the Demobilization Bureau, research and compilation continued and developed into a series of historical monographs.

The paucity of original orders, plans and unit journals, which are normally essential in the preparations of this type of record, most of which were lost or destroyed during field operations or bombing raids rendered the task of compilation most difficult; particularly distressing has been the complete lack of official strength reports, normal in AG or G3 records. However, while many of the important orders, plans and estimates have been reconstructed from memory and therefore are not textually identical with the originals, they are believed to be generally accurate and reliable.

Under the supervision of the Demobilization Bureau, the basic material contained in this monograph was compiled and written in Japanese by former officers, on duty in command and staff units within major units during the period of operations. Translation was effected through the facilities of Allied Translators and Interpreters Service, G2, General Headquarters, Far East Command.

--v--

This Japanese Operational Monograph was rewritten in English by the Japanese Research Division, Military History Section, General Headquarters, Far Bast Command and is based on the translation of the Japanese original. Editorial corrections were United to those necessary for coherence and accuracy.

--vi--

TABLE OF CONTENTS

Page

Chapter I

Period Between Washington Conference and First London Conference

1

Vessel Armament

2

Air Armament

5

Chapter II

First Naval Armament Replenishment Plan

11

Vessel Armament

11

Air Armament

12

Chapter III

Second Naval Armament Replenishment Plan

17

Vessel Armament

18

Air Armament

19

Appendix I

Negotiations between the Navy Ministry and the Navy General Staff regarding the First Naval Armament Replenishment Plan

23

Appendix II

Navy General Staff Secret Document No. 154

47

Appendix III

Outline of Second Naval Replenishment Plan

59

Appendix IV

Disposition of Air Units after Completion of Plan 2 - End of 1936

61

 

 

Chart No. 1

Naval Strength at end of 1924

3

Chart No. 2

Naval Strength - 30 September 1930

6

Chart No. 3

Organization of Air Groups - 1 November 1942

8

Chart No. 4

First Naval Armament Replacement Program 1931 Program

13

Chart No. 5

Vessels Constructed from 1931 to 1933

14

Chart No. 6

Plan 1 - Distribution of Air Strength in Normal Situation

16

Chart No. 7

Dates of Completion of Major Vessels Built under Program 2

20

--vii--

CHAPTER I

Period Between Washington Conference and First London Conference

The Washington Disarmament Treaty was concluded on 6 February 1922. It was foreseen that the effect of this pact would be to greatly weaken the Imperial Navy, consequently naval authorities mapped out plans to overcome these weaknesses by replenishing their strength with naval vessels outside treaty restrictions, as well as by building up air strength.

Each year the Navy submitted proposals and made requests for budgetary allocations. However, from 1922 to 1924, Japan, honoring the Washington Treaty, continued to scrap vessels and make the other modifications provided for in the treaty. At the same time, the Imperial Navy voluntarily undertook the reduction and modification of the auxiliary building program based on the 8-8 Fleet Plans (Plans to keep 8 BB and 8 BC as its fleet's nucleus.) Subsequently, because of the tremendous financial burden placed on the country by the Great Kanto earthquake, the Imperial Navy was forced to postpone the dates of completion of all armament plans. The long-term plan for naval shipbuilding extending from 1911 to 1927 was repeatedly reduced and postponed for financial reasons and rarely got past the planning stage. Naval air power also suffered a considerable setback because of the national trend toward financial retrenchment and disarmament.

--1--

During this period of inertia in naval rearmament even the number of cadets accepted for the Naval Academy was drastically reduced. In 1923 only one-sixth of the 300 students planned for under the 8-8 Fleet Plan were accepted.

Vessel Armament

The period from 1922 to 1924 was regarded as the readjustment period in accordance with the provisions of the Washington Disarmament Treaty.

The Washington Treaty referred to battleships and battle cruisers as capital ships and all other naval vessels as auxiliary ships. In regard to capital ships, ten were to be retained, while ten ships ranging in age from 10 to 20 years, together with six ships under construction and eight still in the planning stage were to be scrapped, disposed of, or maintained for noncombat purposes.

The tonnage of aircraft carriers was so far below the 81,000 maximum that the Kaga and the Akagi were to be reconstructed as aircraft carriers.

Since auxiliary ships were limited only in displacement tonnage and in the caliber of guns, the construction program for such craft was extended by constantly putting off prearranged plans. A Naval strength at the end of 1924, when the readjustment and scrapping of vessels in accordance with the Washington Treaty was completed, was as shown in Chart 1.

--2--

Chart 1 — Naval Strength at end of 1924

Classification

Number of Ships

Total
Standard
Displacement

Battleships

6

184,062 tons

Battle Cruisers

4

105,280 "

Total for Capital Ships

10

289,342 "

Aircraft Carriers

2

12,650 "

Second-class Cruisers

18

82,855 "

Destroyer Tenders

4

21,015 "

Mine Layers

3

17,960 "

First-class Coast Defense Ships

7

59,410 "

Second-class Coast Defense Ships

4

13,615 "

First-class Gunboats

4

4,393 "

Second-class Gunboats

9

2,915 "

First-class destroyers

30

35,495 "

Second-class Destroyers

51

37,510 "

Third-class destroyers

2

640 "

First-class Submarines

1

1,400 "

Second-class Submarines

39

30,842 "

Third class Submarines

10

3,259 "

Special Service Ships

29

292,488 "

Total for Auxiliary Ships

213

616,447 "

GRAND TOTAL

223

905,789 tons

--3--

From 1925 until the London Disarmament Conference in 1930 it was possible to carry out only a minimum amount of construction. The armament program was constantly reduced and the established continuous building program was postponed due to financial difficulties. During this period no new replenishment program was approved by the Diet. Ships actually completed from 1925 to 1930 were as shown hereunder:

Year

Type

Name of Ships

1925

Cruisers

Abukuma, Jintsu, Naka

Destroyers

Yunagi, Oite, Satsuki, Kisaragi, Hayate

Submarines

Three ships

1926

Cruisers

Furutake, Kako

Destroyers

Mutsuki, Fumisuki, Yayoi, Uzuki, Kikuzuki

Submarines

Five ships

1927

Aircraft carrier

Akagi

Cruisers

Aoba, Kinugasa

Destroyers

Minatsuki, Nagatsuki, Mikazuki, Yuzuki, Nechizuki

Submarines

Seven ships

1928

Aircraft carrier

Kaga

Cruiser

Nachi

Destroyers

Isonami, Shinonome, Usugumo, Shirakumo, Fubuki, Shirayuki

Submarines

Four ships

1929

Cruisers

Haguro, Myoko, Ashigara

Minelayers

Shirataka, Itsukushima

Gunboat

Atami

Destroyers

Natsuyuki, Murakumo, Miyuki, Uranami, Shikinami

Submarines

Five ships

1939

Minelayer

Yaeyama

Gunboat

Futami

Destroyers

Ayanami, Asagiri, Amagiri, Yugiri

Submarines

Three ships

The strength of the Imperial Navy on 30 September 1930 was as shown on Chart 2.

The London Treaty for limitations of auxiliary naval vessels was signed on 22 April 1930 and ratified by the Emperor on 2 December 1930. As a result of this treaty, Japan agreed to limit her tonnage to:

A-class cruisers

108,400 tons

B-class cruisers

100,450 tons

Submarines

52,700 tons

The Japanese Navy decided that the obsolete auxiliary vessels, the Aso, Tokiwa, Asama, Yagumo, Izumo, Iwata, Kasuga and Yodo would be treated as special ships outside tonnage limitations, while the Hiei and three cruisers of the Kuma class would be retained as training vessels.

Air Armament

The Japanese Imperial Navy began using aircraft in 1912. However, in spite of their using aircraft aboard the Wakamiya Maru to great advantage in the invasion of Tsingtao during World War I, development of naval aviation was very slow. It was not until 1916 that, together with the organization of the Yokosuka Air Group, a plan for organizing three air units was approved by the Diet with the necessary appropriations. The Sasebo Air Group was established in 1918, and the same year a plan was formulated to add five more air units, bringing the total to eight

--5--

Chart 2 — Naval Strength - 30 September 1930

Classification

Number
of
Ships

Total
Standard
Displacement

Battleships

6

184,080 tons

Battle Cruisers

4

111,320 "

Total for Capital Ships

10

295,400 "

Aircraft Carriers

4

66,450 "

First-class Cruisers

8

68,400 "

Second-class Cruisers

21

98,415 "

Submarine Tenders

4

21,015 "

Mine Layers

5

21,275 "

First-class Coast Defense Ships

7

59,410 "

Second-class Coast Defense Ships

2

6,630 "

First-class Gunboats

2

2,045 "

Second-class Gunboats

11

3,255 "

First-class Destroyers

54

75,125 "

Second-class Destroyers

48

35,070 "

First-class Submarines

22

34,788 "

Second-class Submarines

45

36,185 "

Mine Sweepers

10

7,290 "

Special Service Ships

25

266,798 "

Total for auxiliary Ships

270

802,151 "

GRAND TOTAL

280

1,097,551 tons

--6--

units. In 1920, the plan was increased by a further nine air units, raising the total to 17 units.

The importance of aeronautics was recognized by the Japanese Imperial Navy in 1921 to the extent that upon the advice of a group of highly proficient aeromechanics from Great Britain, drastic changes were made in the method of developing aeronautical techniques. However, the organizational system and technical and military strength of aviation, as well as the over-all setup still failed to meet the requirements of the Navy's plans for building up its forces. Therefore, the execution of the plan for establishing the 17 air units, as well as replenishment of such forces, was delayed until 1930.

At the conclusion of the Washington Disarmament Treaty in 1922, the Imperial Navy was confronted with a situation wherein it was found necessary to reinforce its air strength and make qualitative improvement in armament, along with the replenishment of auxiliary vessels. It selected promising young men and made every effort to bring its air force up to full strength. It drew up and issued an order for the organization of naval air groups on 8 October 1924, to be effective on and after 1 November 1924 (See Chart 3).

In this way the ground work was laid for the building up of air power. The actual replenishment of the air forces, however, did not go beyond the stage of reinforcing end modifying its strength by one and a half units a year, due to the extremely low production of aircraft and the inferiority in techniques and performance, as well as

--7--

Chart 3 — Organization of Air Groups - 1 November 1942

Unit Designation

Classification of Aircraft

No
of
Air
units

Yokosuka Air Group

Airplanes

Seaplanes

Reconnaissance Planes

1.0

Flying Boats

0.5

Carrier Planes

Attack Planes

1.0

Balloons

1.0

Total

3.5

Kasumigaura Air Group

Airplanes

Seaplanes

Reconnaissance Planes

1.0

Training Planes

0.5

Carrier Planes

Reconnaissance Planes

1.5

Land Planes

Training Planes

2.0

Research Planes

1.0

Dirigibles

1.0

Total

7.0

Sasebo Air Group

Airplanes

Seaplanes

Reconnaissance Planes

1.0

Flying Boats

0.5

Total

1.5

Air Group

Carrier Planes

Fighters

1.0

GRAND TOTAL

13.0

Composition of an air unit is fully described in Monograph No. 169.

--6--

to the length of time necessary to train personnel.

By the end of 1930 seventeen units had been organized. These units were designated the "Old Aerial Armament Program" and came under a different classification from units under the first replenishment program. Disposition of these units was made as follows:

Type

Yokosuka

Kasumigaura

Tateyama

Sasebo

Omura

Total

Primary training planes

3.0

3.0

Carrier fighters

0.5

0.5

1.0

2.0

Carrier reconnaissance planes

0.5

1.5

2.0

Carrier attack planes

6.5

1.0

1.0

2.5

Reconnaissance seaplanes

0.5

1.5

1.0

1.5

4.5

Flying boats (small)

0.5

1.0

0.5

2.00

Research planes

1.0

1.0

Total

2.5

7.00

3.5

2.0

2.0

17.0

In addition, one dirigible unit was attached to the Kasumigaura Air Group, Considerable changes in the organization and distribution of aircraft was expected with the establishment of new air groups and the reinforcement of aircraft.

The total number of aircraft available in the 17 units was 284 planes, of which 109 were reserve planes.

--9--

CHAPTER II

First Naval Armament Replenishment Plan

As a result of the London Naval Disarmament Treaty, the Japanese Imperial Navy was permitted to have, in gross weight, almost as much tonnage as it had demanded from Great Britain and the United States. In substance, however, the "A" class cruisers were reduced to a tonnage of about ten percent less than its demand in ratio to the United States Navy, and the submarines were reduced to approximately 25,000 tons in absolute weight.

Having regard to these limitations, the Navy keenly felt the necessity to build the tonnage specified in the treaty as promptly as possible, and also to expand air armament beyond the limit of the treaty. On 7 October 1930, the Navy Minister presented the Prime Minister with a new plan for a complete readjustment and replenishment of major naval strength. The plan, slightly modified, received the approval of the Diet in 1931, end was known as the First Naval Armament Replenishment Plan, or simply as Plan 1. The budget for this plan passed the Diet for a period of six years from 1931 to 1936 totaling 424 million yen. (¥2.5 = $1) (Details of the negotiations conducted between the Navy Ministry and the Navy General Staff regarding the First Naval Armament Replenishment Plan are shown in Appendix I.)

Vessel Armament

The First Naval Armament Replenishment Program included a plan

--11--

to construct 39 vessels with a total tonnage amounting to 72,905 tons, at an expenditure of 247,080,000 yen over six years from 1931 through 1936. (Chart 4) This plan was to be carried out through the redistribution over the six-year period of the budget originally allocated for the construction of auxiliary vessels under the continuous program. By the end of 1933, 25 vessels totaling 74,789 tons had been completed under this program. (Chart 5) Following the Tomozuru Incident in March 1934 and the 4th Fleet Incident in September 1935, it became necessary to make revisions in the designs of some of the vessels to improve their efficiency and strengthen their hulls. The completion of the plan, therefore, was delayed until the end of October 1937.

In 1933 a budget of 15,000,000 yen was passed for the plan known as the 1933 Program, apart from Program I, to construct the submarine tender Taigei and two Class "A" subchasers. Construction on the 10,000-ton tender Taigei was started in April 1933 and completed in March 1944, while construction on the two 300-ton subchasers was started in June 1933, end in March 1944 they too were completed.

Air Armament

In Plan I the Navy General Staff originally had asked for 28 air units. During the course of negotiations with the government, however, this was reduced to 16 unite. Moreover, appropriations for this plan were made on the condition that the construction of two

--12--

Chart 4 — First Naval Armament Replacement Program

1931 Program

Category

Number

Tonnage
per
Vessel

Total Tonnage

Class of Vessel

Date of Commencement

Date of Completion

2d Class Cruiser

4

8,500

34,000

Mogami Class

Oct 31

Oct 37

Destroyer

12

1,368

16,416

Hatsuharu Class 6

May 31

Aug 37

Shiratsuyu Class 6

Submarine

1

1,900

Long Cruising Range

Jun 31

May 37

"

6

1,400

Large size

"

"

"

2

700

11,700

Medium size

"

"

Minelayer

1

4,400

4,400

Okinoshima

Sep 34

Sep 36

Torpedo Boat

4

527

2,108

Chidori Class

Oct 31

Jul 34

Minesweeper

6

492

2,952

No. 13 class

Dec 31

Apr 36

Auxiliary Minelayer

3

443

1,329

Natsushima Class

Dec 31

Sep 34

TOTAL

39

72,905

--13--

Chart 5 — Vessels Constructed from 1931 to 1933

Year

Name of Vessel

Displacement
Tonnage

Commencement
of
Construction

Completion

1931

Sagiri

1,700 tons

28 Mar 29

31 Jan 31

Akebono

1,700 "

25 Oct 29

31 Jul 31

Obore

1,700 "

29 Nov 29

31 Oct 31

Ushio

1,700 "

24 Dec 29

14 Nov 31

1932

Takao

9,850 tons

28 Apr 27

31 May 32

Atago

9,850 "

28 Apr 27

30 Mar 32

Chokai

9,850 "

26 Mar 28

30 Jun 32

Maya

9,850 "

4 Dec 28

30 Jan 32

Yaeyama

1,135 "

2 Aug 30

31 Aug 32

Ikazuchi

1,700 "

7 Mar 30

15 Aug 32

Bazanami

1,700 "

21 Feb 30

19 May 32

Akatsuki

1,700 "

27 Feb 30

30 Nov 32

Inazuma

1,700 "

7 Mar 30

15 Nov 32

Submarine I-5

1,950 "

30 Oct 29

31 Jul 32

Submarine I-65

1,638 "

19 Dec 29

1 Dec 32

Submarine I-66

1,638 "

8 Nov 29

10 Nov 32

Submarine I-67

1,638 "

14 Oct 29

8 Aug 32

1933

Ryujo

7,400 "

26 Nov 29

9 May 33

Hibiki

1,700 "

21 Feb 30

31 Mar 33

Hatsuharu

1,368 "

14 May 31

30 Sep 33

Nenohi

1,368 "

15 Dec 31

30 Sep 33

Chidori

527 "

13 Oct 31

20 Nov 33

Minesweeper 13

492 "

22 Dec 31

31 Aug 33

Minesweeper 14

492 "

22 Dec 31

30 Sep 33

Natsushima

443 "

24 Dec 31

31 Jul 33

--14--

air units be postponed until the 1938 fiscal year or later. This meant that only 14 units would actually be activated by the end of 1936. At that time demands for government appropriations for air armament were not made on the same concrete numerical basis as budgetary demands for the construction of vessels. Considerable difficulty was involved in obtaining aircraft equipment and in the improvement of necessary airfield facilities. The situation was such that even the drastically reduced plan was not completed until the end of October 1937.

The type of aircraft required under Plan I were:

Carrier-borne fighters

2.0 units

Carrier-borne attack planes

6.0 units

Reconnaissance seaplanes

1.5 units

Medium size flying boats

3.0 units

Large size flying boats

1.0 units

Test planes

0.5 units

Total

14.0 units

One hundred and seventy-six (176) planes were required, of which 46 were to be used as replacements.

Because of their frequent transfers, the distribution of the air units among the various air groups cannot be clearly stated. However, in view of the time of establishment, size of the airfields, and their convenience for training, Chart 6 is considered sufficiently correct to show the distribution of air strength in normal situations.

--15--

Chart 6 — Plan 1: Distribution of Air Strength In Normal Situation

Type of Plane

Yokosuka

Kasumigaura

Tateyama

Yokohama

Ominato

Kure

Sasebo

Omura

Saeki

Total

Old
Program

Grand
Total

Primary trainer

0

3.0

3.0

Carrier-borne fighter

0.5

0.5

0.5

0.5

2.0

2.0

4.0

Carrier-borne

reconnaissance

plane

0

2.0

2.0

Carrier-borne attack plane

2.0

0.5

1.0

0.5

0.5

1.5

6.0

2.5

8.5

Reconnaissance Seaplane

0.5

0.5

0.5

1.5

4.5

6.0

Small-size

flying boat

0

2.0

2.0

Medium-size

flying boat

1.0

1.0

1.0

3.0

3.0

Large-size firing boat

1.0

1.0

1.0

Teat plana

0.5

0.5

1.0

1.5

Total

3.5

1.0

2.5

1.0

0.5

2.0

1.0

0.5

2.0

14.0

/

/

Old Program

3.0

7.0

2.5

0.5

1.5

2.0

0.5

/

17.0

/

Grand Total

6.5

8.0

5.0

1.0

1.0

2.0

2.5

2.5

2.5

/

/

31.0

--16--

Japan's foreign relations, which had been deteriorating since the Manchuria Incident, grew worse after her withdrawal from the League of Nations. In view of the forthcoming Disarmament Conference and the expected trend in international affaire, it seemed as though the security of the whole of East Asia would depend upon the real power of Japan. Moreover, with the huge increase in American naval forces, culminating with the first Vinson Program in March 1934, Japan felt a very urgent need to replenish her naval forces. Despite the fact, therefore, that Plan 1 was still in progress, it was decided to put into operation the Second Naval Replenishment Plan, called Plan 2, in order to replenish the naval forces up to the treaty limits at the earliest possible moment. This replenishment program was to be completed in four years from 1934 to 1937. The Navy Minister negotiated with the Finance Minister on several occasions concerning budgetary appropriations for the program, and finally the program was approved by the Cabinet and submitted to the Diet. The budget for the program was set at 477,127,300 yen (¥ 4 - $1) of which 431,688,000 yen was to be used for ship construction, and 45,439,300 yen for creating eight air units. This received Diet approval and, with the Imperial Sanction, was published as law on 20 March 1934. (Appendix II shows communications between the Navy Minister and the Navy General Staff relative to Plan 2, and sets forth the Navy General Staff's requirements to fulfill their proposed plan.)

Vessel Armament

In Plan 2 the Navy General Staff originally asked for an additional 87 ships with a total displacement of 159,370 tons, to include 22 ships of 63,200 tons under the treaty limitations. However, they could not win the full approval of the Finance Ministry in regard to the construction of vessels outside the treaty limitations, although the plan to bring up to maximum strength the vessels coming under the treaty limitations met with little objection from other government agencies.

After prolonged negotiations the Navy was forced to reduce this armament program to a four-year program, in which time they were to build 43 vessels with a total displacement of 137,350 tons. A budget amounting to 431,688,000 yen was finally passed by the Diet for this program. (Outline of the Second Naval Armament Replacement Program is shown in Appendix III.)

A number of ships scheduled in Plan 2 had their keels laid in the latter half of 1934, however, the construction of the Hiryu, Chikuma and Takasaki had to be postponed about one year, mainly because of a shortage of dockyards. This same difficulty was met in the case of destroyers, although the urgent necessity to improve their equipment was realized after the Tomozuru accident.

The tremendous damage suffered by the Fourth Fleet in a typhoon

--18--

in the fall of 1935 clearly showed the necessity for drastic improvement in the construction of all naval vessels. Not only were sweeping changes made in design of all ships under construction, but it was necessary to strengthen almost all ships already commissioned. This, coupled with the execution of the existing plan for remodeling capital ships, caused a rapid increase in naval construction, but at the same time, served to delay the completion of Plan 2 to a very great extent. (Chart 7)

Air Armament

With the completion of the aircraft carrier Ryujo in May 1933, in addition to the Hosho, Kaga and Akagi. the carrier-borne air force acquired great importance as the Navy's main offensive unit. At the same time, aircraft carried by battleships and cruisers also gained in importance as essential means of spotting, scouting and contact. This resulted in a revolutionary change in the concept of sea operations and, with the increasing cooperation of the land-based air force, sea operations in the form of patrol and attack sorties helped greatly to contribute to the idea that aircraft was of tremendous importance in carrying out such operations.

Plan 2 made provision for only eight new units, however, appropriations were made to carry out the reorganization of nine units, and also to move up the completion date of the ten Diet-approved units to the end of the 1936 fiscal year, which was the deadline for the completion of Plan 2. By the end of the 1936 fiscal year,

--19-

Chart 7 — Dates of Completion of Major Vessels

Built under Program 2

Type

Name

Date of Completion

Months Delayed

Remarks

Aircraft Carrier

SORYU

29 Dec 37

"

HIRYU

5 Jul 39

16

Cruiser

TONE

20 Nov 38

8

"

CHIKUMA

20 May 39

14

Destroyer

UMIKAZE Class: 4

31 Aug 37
last ship

"

ASASHIO Class: 10

28 Jun 39
last ship

15

Submarine

Cruising Submarine: 2

5 Dec 38
last ship

9

"

Large Size: 2

18 Dec 38
last ship

9

Seaplane Tender

CHITOSE Class: 2

15 Dec 38
last ship

9

"

MIZUHO

25 Feb 39

11

Submarine Tender

TSURUGIZAKE

15 Jan 39

10

Work for conversion into an aircraft carrier begun about Nov 40, finished Dec 41.

Submarine Tender (aircraft carrier)

TAKASKI

27 Dec 40

33

In the course of building this ship was converted into an aircraft carrier. Finished on 27 Dec 40.

--20--

therefore, the total number of units was to be 39. The eight new units would comprise:

Carrier-borne fighters

3.0 units

105 planes (including 25 planes for replacement.)

Medium attack planes

2.5 units

Large attack planes

1.5 units

Large flying boats

1.0 units

The disposition of the air groups, upon the completion of Plan 2, was provisionally scheduled as shown in Appendix IV.

Only four of the eight land-air groups were completed by the end of the 1936 fiscal year. The completion of the four remaining groups was delayed more than a year. There was from one to two years' delay in the completion of the program for carrier-borne and shipborne aircraft.

Due to the delay in obtaining aircraft material, two of the two and a half units of medium attack planes were not completed until the end of the 1937 fiscal year.

It was only with great effort that a half unit of the 1 1/2 large attack-plane units was completed by the end of the 1936 fiscal year. The performance of this aircraft (Type 95 land-attack planes) was extremely low, and they were completely expended through mishaps during the China Incident before the tactical value of the unit could be shown. The production of this type of plane was discontinued, and, at the same time, an attempt was made to improve the performance of medium attack planes. The execution of the plan for armament of large attack planes was left in abeyance until the middle of World War II, when plans were made for the production of the "Renzan" bombers.

--21--

Despite the fact that the aircraft complement for a flying boat unit was only two aircraft per unit, the completion of one flying boat unit was delayed almost a year due to materiel shortages.

The delay in naval armament caused a delay in the equipment and organization of carrier-borne and shipborne planes from one to two years. With the exception of the special cases stated above, Air Armament Plan 2 was completed by the end of the 1937 fiscal year — about one year after the specified date of completion. The total number of aircraft and personnel at the end of the 1936 and 1937 fiscal years was:

1936 fiscal year

1937 fiscal year

Crews

Planes

Crews

Planes

Land air groups

1,620

519

1,810

563

Carrier-borne and ship-borne planes

701

261

901

332

TOTAL

2,321

780

2,711

895

--22--

Appendix I

Negotiations between the Navy Ministry and the Navy General Staff regarding the First Naval Armament Replenishment Plan

On 27 June 1930, the Chief of Naval General Staff sent the Navy Minister a note with basic recommendations on the replenishment of strength following the London Naval Treaty. Simultaneously, the Vice Chief conferred with the Vice Minister regarding details. On 8 July 1930, the Minister replied to the effect that he would endeavor to realize the complete adjustment and replenishment of strength as far as general conditions, especially the financial situation, would allow. On 11 September 1930, the Chief of the Navy General Staff forwarded to the Navy Minister, Navy General Staff, Secret Document No 176, stressing the need for naval strength. In response to this correspondence the Navy Minister pushed the study of the recommendations and at the same time carried out negotiations with the government in order to obtain the necessary appropriations. On 15 November 1930 the Navy General Staff received a reply from the Navy Ministry stating that owing to the unfavorable state of the national finances the appropriation requests had been cut. It also gave the appropriations to be made to the Navy, and the measures to be taken by the end of 1936 in order to minimize the shortage in strength after the treaty had gone into effect.

--23--

Navy General Staff Secret Document No 176

11 September 1930

From: Chief of the Navy General Staff, TANIGUCHI, Naomi

To: The Navy Minister, TAKARABE, Takeshi

Subject: Recommended plans for construction and replenishment of naval vessels and for the replenishment and expansion of air strength

The above mentioned plans, the contents of which are shown in the appended sheet, were drawn up by the Navy General Staff after careful study, with a view to minimizing tactical handicaps arising from the armed strength agreed upon in the London Naval Treaty. These plans, agreeing in principle with the Reply to the Throne made recently by the Supreme War Council, are absolutely indispensable from the standpoint of national defense and strategic operations. In the light of the strength of naval forces of the major powers subsequent to the conclusion of the London Naval Treaty, and in view of the current naval rearmament of the Empire and future developments, it is considered most imperative from the view of national defense to carry out the replenishment program recommended previously in Navy General Staff Secret Document No 116 of 1930. Such being the case, your efforts toward the completion of these plans upon the conclusion of the London Naval Treaty will be greatly appreciated.

The gist of the Appendix to Navy General Staff Secret Document No 176:

The plan for construction and replenishment of naval vessels (abridged)

--24--

Most effective use is to be made of the forces which the Empire is permitted to retain under the new London Navy Treaty. Efforts are to be exerted toward replenishment of naval vessels not restricted by the treaty.

These plans are to be put into execution during the 1931 fiscal year and completed by the end of the 1936 fiscal year. The construction of ships begun about this time, and restricted by the treaty, is to be completed by the end of December 1936. However, the construction of those ships permitted by the treaty to be under construction at the end of 1936, as well the construction as those ships not restricted by the treaty, is to be begun in 1934 and completed by the end of the 1938 fiscal year.

Replenishment and construction of naval vessels Ships Limited by Treaty

Category

Standard
Displacement
Tonnage

Number
of
Ships
to
be
Constructed

Number
of
Ships
to
be
Started
in
1934

Cruisers

8,500

4

2

Aircraft Carrier

9,850

1

0

Destroyers

1,400

18

7

Submarines

1,900

1

2

1,400

6

2

700

2

0

Remarks

1,900 ton submarine is long cruising range type.

1,400 ton submarine is Navy-type large.

700 ton submarine is medium type.

--25--

Ships Outside Treaty Limitation

Category

Standard
Displacement
Tonnage

Number
of
Ships
to
be
Constructed

Number
of
Ships
to
be
Started
in
1934

*Coast-defense ships

1,200

4

0

Gunboats

900

2

0

200

1

0

Mine Layers

5,000

2

0

2,000

0

2

Auxiliary Mine Layers

600

5

3

Torpedo Boats

600

12

8

Mine Sweepers

600

6

6

Emergency-net Layer

2,000

0

1

Net Tenders

600

0

2

Submarine Chasers

300

2

4

150

4

2

Repair Ship

10,000

1

0

Oil Tanker

17,000

1

0

Survey Ships

1,600

2

0

Submarine Tender

8,000

1

0

Collier

10,000

1

0

* Substitute for destroyer

--26--

Twenty-eight additional air units were to be reinforced under the plan for the replenishment of air strength.

In response to the foregoing, Navy Ministry authorities pushed the study of the recommendations. At the same time, they carried out negotiations with the Government. As a result, the Ministry sent the following answer on 15 November 1930:

Secretariat Secret Document No 1090

15 November 1930

From: Navy Minister ABO, Kiyotane

To: Chief of the Navy General Staff, TANIGUCHI, Naomi

Subject: Readjustment and Replenishment of Major Naval Strength

Upon presentation to the Prime Minister of a request of 7 October in regard to the subject mentioned in your Navy General Staff Secret Documents Nos 176 and 116, conferences were held by the executives of this Ministry and the general staffs. (See Appendix I) Due to the unfavorable state of national finances, the requests were slashed. Efforts were made, thereafter, to realize your proposals through repeated negotiations with the state ministers concerned.

As a result of these negotiations, a decision was reached at a Cabinet Meeting on the eleventh of this month. (See Appendix 2)

Incidentally, I will confer with the Prime Minister on the replenishment of armament not approved at this Cabinet Conference.

--27--

Appendix No. 1

Secretariat Secret Document No 943

7 October 1930

From: Navy Minister Baron ABO, Kiyotane

To: Prime Minister HAMAGUCHI, Yuko

Subject: Communication with reference to readjustment and Replenishment of Major Naval Strength

For various reasons not all of our recommendations were accepted at the London Naval Disarmament Conference. Therefore, it was anticipated that defects would appear in the forces which were to be used to carry out the naval operations program based upon the established national defense policy. This issue created a sensation across the length and breadth of the nation. Even in the Navy itself confusion arose over the issue and the situation was such that no one could foretell what the outcome would be. However, the fact that the situation appears to have settled outwardly is believed attributable to confidence felt in the sincerity of the government in naval rearmament matters.

I believe that the following are the principal causes contributing to the resolution of the issue.

When a Cabinet meeting was held on 1 April this year to discuss the instructions to be given to the Imperial Plenipotentiary, the Cabinet approved the Navy Vice-Minister's plan for easing difficulties expected in the strategic employment of forces for national defense as the result of the disarmament pact. Heated discussion ensued and

--23--

there appeared no end to the arguments during the unofficial meeting of the Supreme War Council held on 21 July to discuss whether the military strength authorized by treaty would hinder the strategic employment of forces for national defense, and the measures to be taken to correct the situation. On this occasion the Prime Minister, who had received situation reports from the ex-Minister of the Navy, declared that the government would, considering finances and other factors, make the utmost effort toward the realization of the rearmament program.

From this statement, the Supreme War Council understood the sincere attitude of the government and submitted a Reply to the Throne which was passed unanimously at the 23 July conference. The Prime Minister, shown the Reply by the Emperor, also replied to the Emperor, saying, "The reply of the Supreme War Council is just and right. I shall do my utmost to assist the Imperial Rule by carrying out the program, after careful deliberation with other cabinet ministers on the financial and other aspects of the program."

Needless to say, armament must be based upon national strength. Nevertheless, national defense is a matter which should be treated as a long-range policy of the nation, and at the same time the enhancement of national prestige and authority must be backed by powerful armament. For this reason, the greatest care should be exercised to see that the current financial hardships do not make one oblivious to the great necessity for rearmament. There is a danger that once rearmament is neglected, the day may come when a

--29--

regrettable situation could not be rectified. Considering the manner in which circumstances have developed to date, I firmly believe that from the standpoint of keeping the dignity of the government and exercising control over the Navy it is most imperative at this juncture to establish rearmament in line with the Reply to the Throne made by the Supreme War Council.

It is a cause of great anxiety to this minister that there are those who are apt to make light of rearmament, regarding the conclusion of the Disarmament Treaty as the advent of international peace. It is my belief that the United States will maintain a commanding position in the near future in naval armament. According to intelligence reports received to date, the program for auxiliary vessels proposed by the General Board, U. S. Navy, as shown in the appendix, aims at maximum buildup within limits of the treaty. In the case of capital ships, budgetary appropriations amounting to over 98,000,000 yen for remodeling ten dreadnoughts have already been approved by Congress, while the remaining capital ships are scheduled shortly to be modernized at the great cost of approximately 140,000,000 yen. Meanwhile, in the case of the air arm, U.S. Navy authorities are pressing for a goal of 1,000 aircraft as a second phase plan, in addition to the established program for the construction of 1,000 planes. From these facts one cannot help but conclude the disarmament treaty has not altered in the least the U. S. attitude toward naval rearmament.

Unless our country establishes and executes immediately a proper

--30--

naval armament replenishment program to cope with the situation, there is a likelihood that the gap in naval strength between Japan and the United States will widen increasingly, and our Just and rightful contentions will not be accepted, and we will fall prey to an overwhelmingly superior force. So far as our country is concerned, the maximum strength permitted under the treaty is inadequate from the standpoint of strategic employment of forces. We should try, therefore, to make most effective use of forces permitted by the treaty. Not only that, but the shortage of submarines and 8-inch cruisers should be rectified. At the same time, air strength should be reinforced in order to meet the requirements of national defense.

In line with the foregoing the Navy General Staff, after careful deliberation, mapped out the plan mentioned below and communicated it to the Navy Ministry. After several exchanges of opinion between the Navy General Staff and the Navy Ministry, it was agreed that the plan was right in principle.

I should like to add that the plan in question was presented as explanatory data on the occasion of the Supreme War Council's meeting to discuss measures to cope with the Naval Disarmament Treaty.

It is estimated that the implementation of this plan will cost as much as ¥ 733,633,000 in extraordinary expenditures alone. However, by reason of the points cited in the foregoing, it is desired that consideration be given to and every effort exerted for the realization of the plan, despite the fact that the implementation

--31--

of the plan in the present financial condition of the nation and financial policies pursued by the government is difficult.

Extract from the Naval Rearmament Program

The following plans are scheduled to be put into effect during the period from the 1931 fiscal year to the 1936 fiscal year:

Item

Necessary Expenditure

Shipbuilding & replacement program

¥ 422,983,000

Air strength reinforcement program

131,508,456

Various kinds of improvement programs

179,142,101

Total (Extraordinary expenditure)

¥ 733,633,557

Shipbuilding and Replacement Program

In view of the appearance of numerous superior warships of modern design in the United States, efforts must be directed toward minimizing the actual lowered effectiveness of the naval forces at the disposal of the Empire. Every possible effort must be made to build up forces to the limits prescribed by the treaty. At the same time, individual naval craft should be brought to maximum effectiveness. Meanwhile, replenishment of naval vessels not limited by treaty should be effected with a view to offset the difficulties imposed upon our strategic employment of forces by the treaty.

--32--

This program will be launched in the 1931 fiscal year and accomplished by 31 December 1936. The program concerning warships limited by treaty is to be accomplished by the end of the 1936 fiscal year. The construction of naval vessels limited by treaty to be under construction at the end of 1936 as well as those vessels not limited by treaty but which require construction during the period in question, is to be initiated in 1934 and completed by the end of the 1938 fiscal year.

--33--

SHIPBUILDING PROGRAM

Warships subject to the treaty limitations

Category of Warship

Standard Displacement

Unit Construction Cost

Number of Vessels to be Constructed and Construction Cost

Number of Vessels Scheduled to be started in 1934 and completed after 1937, and Construction Cost

Tons

¥

¥

¥

Cruisers

8,500

26,141,000

(4) 104,564,000

(2) 52,282,000

Aircraft carriers

9,800

29,000,000

(1) 29,000,000

0

Destroyers

1,400

5,750,000

(8) 103,500,000

(7) 40,250,000

Submarines

Large Cruising Ships

1,900

8,646,000

(1) 8,686,000

(2) 17,372,000

Navy Type Large Size

1,400

6,764,000

(6) 40,584,000

(2) 13,528,000

Medium Size

700

4,172,000

(2) 8,744,000

0

Total

Tonnage

Tons

Tons

Building

80,700

33,400

Cost

¥ 295,078,000

¥ 123,432,000

Warships not limited by treaty.

Coast-defense Ships

9,388,000

0

Large

900

2,217,000

4,435,000

0

Small

200

707,000

707,000

0

Mine Layers

5,000

7,650,000

15,300,000

0

2,000

4,709,700

0

9,419,400

Auxiliary Mine Layers

600

1,909,000

9,545,000

5,727,000

Torpedo boats

600

2,800,000

(12) 33,600,000

(8) 22,400,000

Mine Sweepers

600

1,880,000

11,280,000

(6) 11,280,000

Emergency Net layers

2,000

4,176,900

0

(1) 4,176,900

Net layers

600

1,798,000

0

(2) 3,596,000

Submarine Chaser, Large

300

1,600,000

(2) 3,200,000

(4) 6,400,000

Submarine Chaser, Small

150

1,131,000

(4) 4,524,000

(2) 2,262,000

--34--

Shipbuilding, Program

Warships not limited by treaty - Cont'd

Category of Warship

Standard Displacement

Unit Construction Cost

Number of Vessels to be Constructed and Construction Cost

Number of Vessels Scheduled to be started in 1934 and completed after 1937, and Construction Cost

Tons

¥

¥

Repair Ships

10,00

6,900,000

(1) 6,900,000

0

Oil Tanker

17,000

9,246,000

(1) 9,264,000

0

Collier

10,000

4,080,000

(1) 4,080,000

0

Submarine tender

8,000

10,500,000

(1) 10,500,000

0

Survey Ships

1,600

2,600,000

(2) 5,200,00

0

Total

Tonnage

Tons

Tons

78,000

18,900

Construction Cost

¥ 127,905,000

¥ 65,261,000

Grand

Total

Tonnage

Tons

Tons

159,000

52,300

Construction Cost

¥ 422,983,000

¥ 188,693,300

--35--

Of the amount shown in the foregoing table 422,983,000 yen represents the construction cost for the warships to be constructed by the end of the 1936 fiscal year. The construction cost of the warships to be constructed during the period between 1934 and the fiscal year of 1938 is omitted, according to the existing precedent of the continuing expenditure program.

The estimated expenditure by fiscal year is as follows:

Fiscal year

"

"

"

"

"

1931

1932

1933

1934

1935

1936

20,000,000

67,000,000

90,000,000

90,000,000

83,000,000

72,983,000

Total 422,983,000

In order to build the naval vessels allowed under the London Naval Treaty according to the standard ship age, the following average annual construction tonnage must be undertaken.

Category Auxiliary Ship

Tonnage permitted by Treaty

Ship Age for Replacement

Average Annual Tonnage Construction

8-in Cruisers

108,400 tons

20

5,420 tons

Light Cruisers

100,450 "

20

5,022 "

Destroyers

105,500 "

16

6,594 "

Submarines

52,700 "

13

4,054 "

Total

367,050 tons

21,091 tons

In addition to the above, there is need for the construction of

--36--

a large tonnage of replacement vessels in the categories of battleships, aircraft carriers and ships not restricted by treaty.

The number of the exempt ships to be constructed under the current program looms large compared with the annual construction of only 13,450 tons for auxiliary ships. Thus far, obsolete vessels have been used for defense and local operations, but since the London Treaty prohibits the possession of any vessel, even an obsolete vessel, in excess of limitations, it has become necessary to meet the depletion, as well as to construct new ships as replacements, so that normal peacetime duties may be carried out. The situation is such that it has become absolutely necessary to meet the shortage of submarines by use of certain vessels not limited by treaty. These points were taken into consideration when the program was formulated. To lower markedly our shipbuilding capacity and carry out a retrenchment of facilities and cut down personnel would not only bo difficult but would prove highly disadvantageous in the event that the necessity should arise in later years to revise shipbuilding at a moments' notice.

Air Strength Reinforcement Program

Air unite are to be increased by 16 units at a cost of 85,184,852 yen as a counter-measure to our limited naval strength, caused by the London Treaty.

Twelve air units at a cost of 46,323,604 yen are to be built, irrespective of the London Treaty, in view of the expansion of the US naval air force.

--37--

Various Plans for Replenishment

The following appropriations are considered necessary for vital programs and should be implemented at once and realized by the 1936 fiscal year:

Item

Amount

1.

Expenditure for improvement and modernization of warships and equipment, and incidental expenses

88,933,474 yen

2.

Expenditure for special ship repairs to prolong ship age and expenditure for ordnance repairs

33,560,000 yen

3.

Expenditure for replenishment of air force

9,502,194 yen

4.

Expenditure for increasing submarine force

6,125,500 yen

5.

Expenditure for equipment of research agencies

7,330,358 yen

6.

Increased expenditure for training and promotion of military effectiveness

6,690,575 yen

7.

Expenditure for improvement of defense facilities

27,000,000 yen

Total

179,142,101 yen

In addition to the foregoing, about 40,000,000 yen is being requested as running expenses, mainly for further training of personnel (air maintenance cost not included).

Should it prove impossible to realize Program No. 1 mentioned above by the 1936 fiscal year, it is desired that approval be given

--38--

to the implementation of the subscribed program, and that items of the original program be enforced successively as the financial situation improves.

The urgent program for the replenishment of the Navy. (Extract) It is planned that the following will be carried out during the period from the 1931 fiscal year to 1936 fiscal year.

Item

Necessary Expenses

Shipbuilding and replacement program

355,478,000 yen

Air strength reinforcement program

65,000,000 "

Various replenishment programs

80,000,000 "

Total (Extraordinary expenditure)

500,678,000 yen

--39--

Shipbuilding and replacement program

Category of warship

Standard
Displacement

Unit
construction
cost

No
of
ships
to
be
constructed.

Total
cost.

Warships
subject
to
the
treaty
limitation.

tons

yen

Cruisers

8,500

26,141,000

4

104,564,000 yen

Aircraft-carriers

9,800

29,000,000

1

29,000,000

Destroyers

1,400

5,750,000

18

103,500,000

Submarine-boats

Long cruising range type

1,900

4,444,000

1

4,444,000

Navy type large size

1,400

6,764,000

6

40,584,000

Medium size

700

4,372,000

2

8,744,000

Total

Tonnage:

80,700 tons

295,078,000 yen

Warships
on
the
exempt
list

Coast-defense ships

900

2,100,000

1

2,100,000

Gunboats

Large

900

2,000,000

1

2,000,000

Small

200

600,000

1

600,000

Minelayer

3,500

5,000,000

1

5,000,000

Minelayer

5,000

7,000,000

1

7,000,000

Light minelayers

600

1,700,000

5

8,500,000

Torpedo boats

600

2,600,000

8

20,800,000

Minesweepers

600

1,700,000

6

10,200,000

Submarine chasers (Small)

150

900,000

2

1,800,000

Survey ships

1,600

2,400,000

1

2,400,000

Total

Tonnage

23,400 tons

60,400,000 yen

Grand Total

Tonnage

104,500 tons

355,478,000 yen

Annual average for six years

Teenage

17,412 tons

59,246,000 yen

--40--

The estimated expenditure by fiscal year is as follows:

Fiscal year

"

"

"

"

"

1931

1932

1933

1934

1935

1936

yen 20,000,000

yen 75,000,000

yen 75,000,000

yen 75,000,000

yen 65,486,000

yen 44,992,000

Total 355,478,000 yen

Air strength replenishment program

The 16 units program: 65,000,000 yen.

Various replenishment programs

Expenditure: 80,200,000 yen

Appendix No. 2

Cabinet Decision Concerning Increase and Replenishment of Principal Naval Strength

11 November 1930

This program called for an expenditure of 424,000,000 yen, including 50,000,000 yen reserved for the construction and maintenance of two hew air units in and after the 1938 fiscal year. 247,080,000 yen was to be appropriated over six consecutive fiscal years from 1931 through 1936, for the construction of 39 naval vessels with a total tonnage of 75,300 tons, comprising 25 ships of those types placed under treaty limitations and 14 of those types outside the limitation.

The details are shown in the following table:

--41--

Urgent Program Increase and Replenishment of Principal Naval Strength

Classification

Expenditure

Remarks

Naval Vessels Construction and Replacement Program

247,080,000 yen

In addition 50,000,000 yen
appropriated for construction
of 2 air units, their maintenance, etc.

Air Strength Increase Program

81,970,000

Miscellaneous Replenishment Program

44,950,000

Total

374,000,000

50,000,000

For reference, the allocation of auxiliary naval vessels in total tonnage to Japan, Great Britain and the United States under the London Treaty is shown in the following comparison tables, (A) and (B), and the reply to the Throne made by naval members of the Supreme War Council upon the conclusion of said treaty is in (C).

--42--

(A) Comparative Table of Naval Craft Tonnage held by U. S. and Japan

Type of Vessel

Tonnage held by U.S.

Tonnage claimed by Japan

Tonnage limit under treaty

Difference
between claim
and treaty tonnage

Tonnage

Ratio (%)

Tonnage

Ratio (%)

Class-A Cruisers

180,000

126,000

70.00

108,400

60.22

17,600 ton

Class-B Cruisers

143,500

164,498

56.05

100,450

70.00

41,452

Destroyers

150,000

105,500

70.33

Submarines

52,700

77,842

Tonnage
considered
absolutely
necessary

52,700

100.00

25,142

Total

526,200

368,340

70.00

367,050

69.75

1,290

(B) Comparative Table of Naval Craft Tonnage held by Great Britain and Japan

Type of Vessel

Tonnage held by Britain

Tonnage claimed by Japan

Tonnage limit under treaty

Tonnage

Ratio (%)

Tonnage

Ratio (%)

Class-A Cruisers

146,800

126,000

85.83

108,400

73.84

Class-B Cruisers

192,200

164,498

48.07

100,450

52.26

Destroyers

150,000

105,500

70.33

Submarines

52,700

77,842

Tonnage
considered
absolutely
necessary

52,700

100.00

Total

541,700

368,340

68.00

367,050

67.75

--43--

(C) Reply to Throne adopted at meeting of the Supreme War Council concerning national defense in connection with Japanese naval strength as stipulated in London Treaty of 1930.

On 23 July 1930, a meeting of navy members of the councillors which was held in the Imperial Court, unanimously passed the following reply to the Throne: (Those present: Fleet-Admiral Togo, His Imperial Highness, Prince Fushimi, Councillor Okada, Councillor Kato, Minister, Chief of Navy General Staff, Chief of Operational Bureau, Chief of Military Affairs Bureau, Sumiyama, Aide to His Majesty.)

Reply to the Throne

The national defense policy sanctioned by Your Majesty in 1923 is the best policy to meet the present situation of the Empire. However, the recently concluded London Treaty creates a shortage in our naval strength required for the maintenance and execution of naval operation plans according to the established policy.

Accordingly, in order to minimize the effect of this shortage in strength after the treaty has gone into effect, the following measures must be taken by the end of 1936:

1. The full realization of the tonnage quotas stipulated in the treaty, improvement in the maintenance and of the potentiality of the existing naval vessels, and the increase of craft of those types which are outside the treaty limitation.

2. The expansion of air strength to an extent necessary for

--44--

the execution of the operation plan.

3. The improvement of defense installations, the strengthening of experimental and research organs, the improvement of training facilities, the encouragement of maneuvers and exercises, the increase of personnel and materials, the completion of land and sea installations, and the strengthening of preparations for tactical operations.

The enforcement of these measures is considered almost sufficient under the present situation to secure national defense, despite the restrictions imposed by the treaty. Nevertheless, since the disposition of the military forces of one nation should be determined according to the nation's own estimate of the situation in view of the nature of preparedness, we see it highly disadvantageous from the standpoint of national defense to remain for a long time under the restrictions imposed by this treaty. For this reason, we believe that the Empire should renew its efforts, upon the expiration of the treaty, for the completion of its defense setup with whatever policy is considered to be the best.

We submit this reply with the utmost reverence and humility.

23 July 1930

Signed by the Supreme War

Councillors

--45--

Appendix II

Navy General Staff Secret Document No 154

6 May 1933

From: Navy General Staff

To: The Navy Minister

Subject: Replenishment of Armament during and after the 1934 Fiscal Year

The international situation of the Empire has undergone unprecedented change since her withdrawal from the League of Nations, and the security of East Asia has come to depend entirely upon the actual power of the Empire.

Under these circumstances, the Japanese-American conflict of policies toward the Manchurian issue shows no sign of heading towards amicable settlement. Not only that but it appears that preparations for a solution by force of arms are being made in the United States. This is evidenced by the fact that her armament has steadily been increased since the Manchurian Incident and that her entire fleet has been concentrated on the Pacific coast, while air bases for use in time of war are being sought in central and southern China. Hereafter there may be some changes in the situation for better or for worse, but we must be prepared for the worst, as the general trend of affairs seems to be precipitating a crisis.

In view of the above-stated situation, it is deemed absolutely necessary that a national defense set-up strong enough to cope with

--47--

the crisis be created by supplementing, in the case of the Navy, the numerical inferiority of armament through the improvement of their quality, in addition to replenishment of air strength and warship construction during and after 1934 as envisaged in the communication, Navy General Staff Secret Document No 215 of 1932.

Your utmost efforts in the matter are hereby requested. (Postscript)

1. As to the construction of warships and the replenishment of air strength, it is expected that subsequent developments may require some modification of plans, at which time it is hoped to make further recommendations.

2. It is the intention of the Navy General Staff to have the Vice-Chief of the Navy General Staff confer with the Vice-Minister of the Navy on details of this communication.

Navy General Staff Secret Document No 199

14 June 1933

From: Chief of the Navy General Staff

To: Minister of the Navy

Subject: Construction and Replenishment of Naval Vessels and Replenishment of Air Strength

Navy General Staff Secret Document No 154 was forwarded to you previously with a view to coping with the general trends of future affairs. The steps which should be taken during and after 1934 in replenishment of armament were set forth in that communication. In view of steps now being taken by the United States to meet the new

--48--

situation in the Far East, especially in the light of their plans to push the replenishment of naval forces, it was deemed necessary to modify a section of plans outlined in Navy General Staff Secret Document No 215 of 1932. After careful deliberations, a plan envisaging the construction and replenishment of naval vessels as well as the augmenting of aerial forces, as given in the appended sheet, was formulated in order to effect adequate national defense and meet the international defense situation faced by our nation.

Your utmost efforts toward the realization of this plan are hereby requested.

--49--

Appendix to Navy General Staff Secret Document No 199

12 June 1933

From: Navy General Staff

Plan for Construction and Replenishment of Naval Vessels and Increase of Air Strength

1. In view of the Empire's international situation, brought about by the Manchurian Incident, and in anticipation of the various complications likely to arise during the forthcoming Disarmament Conference and subsequent to the expiration of the period of our notification of intention to withdraw from the League of Nations, there is a strong likelihood that Japan will face a still graver situation around 1935. Therefore, there is urgent need to replenish and equip the absolutely necessary forces to cope with the situation and provide adequate national defense.

However, the equipment of such forces, at this juncture, is impossible to accomplish immediately due to restrictions set forth in the London Treaty. Therefore, wherever possible, the execution of operations is to be facilitated by countering US naval rearmament by replenishing our forces within treaty limits, in accordance with the principles set forth in the Reply to the Throne made by the Supreme War Council at the time of the conclusion of the treaty in question.

Moreover, plans are to be formulated to see that our carrier-borne aircraft will not be inferior to those of the US Navy.

2. In the event that the US Navy's ship construction volume exceeds current expectations prior to the expiration of the London

--50--

Treaty, reinforcement of emergency air units is to be effected, while construction of vessels which are placed outside the limits is to be increased.

3. The plan is to be set into operation in the 1934 fiscal year and accomplished by the end of the 1936 fiscal year. However, the construction of one aircraft carrier and such types of vessels on which construction can be started, but which are not permitted under the treaty to be completed until the end of 1936, are scheduled to be completed at the end of the 1937 fiscal year.

Plan for Construction and Replenishment of Naval Vessels

Construction of naval vessels of restricted categories is to be carried out up to the limits prescribed by the treaty.

In the construction of naval vessels outside treaty limits, priority is to be given to the build-up of first line combat units, while in the case of defensive units, replenishment is to be made by employing, for the time being, obsolete vessels. At the same time forces are to be maintained at the minimum required strength in anticipation of an outbreak of hostilities.

Efforts are to be directed toward reinforcing cruising range and maneuverability of first line combat units.

--51--

SHIPS TO  BE CONSTRUCTED UNDER THE REPLENISHMENT PROGRAM

Ships Restricted by Treaty

Classification

Unit standard displacement Tonnage

Number of Ships

Maximum speed
(knots)

Cruising Range

Standard Armament

Description

Aircraft Carriers

10,050 tons

2

36

10,000 nautical miles at 10 knots

1. 20 mm guns 5 (equipped along center line)

2. 12.7 cm AA guns 20

3. Over 40 AA Machine guns

4. Aircraft (omitted)

1.  Internal combustion engines are to be used if possible.

2.  Number of planes that will be ready on the flight dock at any one time will consist of more than one half of the aircraft complement. Equipment will be so designed as to speed the take off and landing of the planes and also operation of the carrier. For this purpose, the number of planes in reserve may be decreased when necessary.

Cruiser Class-B

8,450 ton

2

10,000 nautical miles at 18 knots

1. 15.5 cm gun—triple mount 5 turrets

2. 12.7 cm AA guns—8

3. AA Machine guns—over 12

4. 61 cm Torpedoes—6 tubes mounts (broadside, upper deck)

5.  Catapults—4

6.  Aircraft-4

--52--

Ships to be Constructed under the Replenishment Program

(Ships Restricted by Treaty) - Cont'd

Classification

Unit standard displacement

Number of Ships

Maximum
speed

(knots)

Cruising Range

Standard Armament

Description

Destroyers

1,330 ton

14

over 36

4,500 nautical miles at 18 knots

1.  12.7 an guns—6

2. Over 4 AA Machine guns

3. 61 cm Torpedoes-8 tubes mounts

Submarines

1,900 ton

2

More than 21 on surface

14,000 nautical miles at 16 knots

1. 53 cm Torpedo tubes— 4 (bow)—2 (stern)

2. 12.7 cm AA guns—2

3. Anti-aircraft Machine guns more than 2

4. Catapult-1 Reconnaissance plane—1

1,400 tan

2

Over 23 surface

10,000 nautical miles at 16 knots

1.  53 on Torpedo tubes— 4 (bow)—2 (stern)

2. 10 cm AA guns more than 2

--53--

SHIPS NOT LIMITED BY TREATY

Classification

Unit
standard
displacement tonnage

Number
of ships
to be
constructed

Maximum
speed
(knots)

Cruising range
nautical miles

Description

Oil Tankers

10,000 ton

2

20

10,000 at 10 knots

Further Separate Communication

Seaplane Tender

9,000 "

3

20

8,000 at 16 knots

Torpedo Boats

600 "

16

34

3,000 at 6 knots

1. 12.7cm guns

4

2. AA Machine cans

more than 2

3. 61cm Torpedoes

4 tubes mounts

Submarine Chasers

300 "

20

1,500 at 14 knots

1. 40mm automatic cannon

2

2. Depth charges, depth-charge projector

(omitted)

150 "

12

20

i

500 at 14 knots

1. 40mm automatic cannon

1

2. Depth charges, depth-charge projector

(omitted)

Gunboats

1,000 "

2

20

more than
2,500 at 14 knots

1. 15cm guns

2

2. 15cm gen

1

3. AAMG

1

4. Internal-combustion engine used

200 "

1

18

over 1,500 at 14 knots

1. 15cm gun

1

2. AA Machine guns

more than 2

3. Internal-combustion engine used

Mine layers

5,000 "

1

20

5,000 at 14 knots

1. 15cm guns

4

2. Mines

omitted

3. AAMG

more than 4

--54--

Ships not limited by Treaty - Cont'd

Classification

Unit
standard
displacement

Number
of ships
to be
constructed

Maximum
speed

(knots)

Cruising
range
nautical
miles

Description

Repair ship

10,000 ton

1

10

8,000 at 14 knots

1. 12.7cm AA guns

4

2. AA Machine guns

more than 4

Emergency net
layer

2,000 "

1

20

2,000 at 14 snots

1. 12.7cm antiaircraft guns

3

2. Type 14 antisubmarine nets

(omitted)

3. AA Machine guns

as required

4. Depth-charge projectors

(omitted)

5. Depth-charges

as required

Coast-defense
ship

1,200 "

4

20

more than
5,000 at 14 knots

1. 12.7cm AA guns

4

2. AA Machine guns

as required

3. Depth-charge projectors

(omitted)

4. Depth-charges

as required

Minesweeper

600 "

6

more
than
20

3,000 at 14 knots

1. 12.7cm AA guns

3

2. AA Machine guns

as required

Survey ships

1,600 "

2

20

5,000 at 14 knots

1. 12.7cm AA guns

4

2. AA Machine guns

as required

Mine layer

2,000 "

1

20

3,000 at 14 knots

1. 12.7cm AA guns

3

2. Mines

(omitted)

3. Depth-charge

(omitted)

4. Dept-charge projectors

(omitted)

5. AA Machine gene

as required

Auxiliary
Mine
layer

450 "

5

more
than

20

1,500 at 14 knots

1. 40mm automatic cannon

2

2. Mine

(omitted)

3. Dept-charge projectors

(omitted)

4. Depth-charges

as required

--55--

Ships not Limited by Treaty - Cont'd

Classification

Unit
standard
displacement
tonnage

Number
of ships
to be
constructed

Maximum
speed

(knots)

Cruising
range
nautical
miles

Description

Net Tender

600 ton

2

20

1,500 at 14 knots

1. 40 mm automatic cannon

2

2. Nets

(omitted)

--56--

The plan for increasing air strength:

1. Purport

a. Aircraft carriers and plane-carrying ships (excluding escort carriers and converted vessels) are to be replenished so as to retain in peacetime all the crew which may be needed in wartime.

b. The replenishment and reinforcement of projected land-air groups is to be carried out so that air crew members will be available to man escort carriers, converted vessels and air groups (including specially established air groups) in the event of war.

c. Air reservists (including personnel in the first and second reserves) are to be replenished in addition to the rapid training of air crew members, should the occasion require, as no time is to be lost in augmenting the shortage of the crew which we might need in wartime.

2. (omitted)

3. Land air groups

(First part omitted)

a. Nine understrength units among the existing air groups are to be reorganized.

b. Among the projected groups, 3 1/2 groups are scheduled for completion in the 1936 fiscal year.

c. Eight new groups are to be established.

d. The 21 existing groups, 10 projected groups, and eight groups to be reinforced, are to be equipped by the 1936 fiscal year.

4. Air reservists (including those in the first and second

--57--

reserves) who are subject to call in wartime and are capable of assuming various air duties after supplementary training of less than five months, are to be assigned to units cited in paragraph c, above

--58--

APPENDIX III

OUTLINE OF SECOND NAVAL REPLENISHMENT PLAN

Category

Number of Vessels

Tonnage per Vessel

Total Tonnage

Class of Warship

Keel Laid

Completed

Aircraft carrier

2

10,050

20,100

Hiryu Class

Nov 1934

Jul 1939

Light cruiser

2

8,500

17,000

Tone Class

Dec 1934

hay 1939

Destroyer

14

1,368 (4)

20,472

Shiratsuyu Class (4)

May 1935

Jun 1939

(Usikaze and others)

1,500 (10)

Asashio Class (10)

Submarine

4

1,950 (2)

6,700

Large Cruising Type (2)

1,400 (2)

Navy Type Large size (2)

Sep 1934

Dec 1938

Seaplane tender

3

9,000

Chitose Class and Mizuho

Nov 1934

Feb 1939

Submarine tender

2

12,000

24,000

Tsurugizaki Class (Takasaki
was converted into an aircraft
carrier in the course of building)
Originally designed as tankers
(9,500 x 2 - 19,000) converted into
submarine tenders on 15 Sep 38

Jan 1938

Dec 1940 (Aircraft carriers)

Torpedo boat

16

595

9,520

Otori Class (8)

Nov 1934

Sep 1937

Cancelled (8)

Submarine chaser

4

270 (1)

780

No. 1 Class (1)

Apr 1935

Jul 1939

170 (3)

No. 51 Class (3)

--59--

Outline of Second Naval Replenishment Plan - Cont'd

Category

Number of Vessels

Tonnage per Vessel

Total

Class of Warship

Keel Laid

Completed

Repair ship

1

9,000

9,000

Akashi

Jan 1937

Total

48

134,572

A four-year program with a budget of 431,688,000 yen was approved.

--60--

Appendix IV

Disposition of Air Units After Completion of Plan 2 - End of 1936

Program

Old Program (17 units)

Program NO. 1 (14 units)

Program No. 2 (8 units)

Grand Total

Number of units after Reorganization

Description

Location

Type of Aircraft

Yokosuka

Tateyama

Kasumigaura

Sasebo

Omura

Ominato

Konoya

Meizuru

Chinkoi

Total

Yokosuka

Tateyama

Kasumigaura

Yokohama

Chinato

Kure

Sasebo

Omura

[entire column unreadable]

Total

Yokosuka

Yokohama

[]

Chinato

Saeki

Omura

Kanoya

Total

Land Trainer

1/2

2 1/2

3

3

3

Reorganized and strengthened from 2 carrier-born reconnaissance plane units, 1/2 carrier-borne units, 1/2 carrier-borne attack plane [ ] unit & 1/2 small size flying boat unit.

Sea
trainer

1/2

2 1/2

3

3

3

Carrier-borne fighter

1/2

1/2

1

2

1/2

1/2

1/2

2

1/2

1/2

1/2

1

2 1/2

6 1/2

6 1/2

Carrier-borne bomber

1/2

1/2

1 1/2

1/2

2

2

Carrier-borne
attack plane

1

1

1 1/2

1

1/2

1/2

5

5

Medium-size attack plane

1

1/2

1/2

1/2

2 1/2

1/2

(1/2)

(1/2)

(1)

1/2 (2)

3 (2)

5

Reorganized and added from 1 1/2 small-size flying boat units.

Large-size
attack
plane

1 (1)

1/2 (1)

1/2 (1)

1 1/2

Reconnaissance
seaplane

1/2

1/2

1

1/2

1/2

1/2

4

1

1/2

1/2

[ ]

6

6

Small-size flying boat

1/2

1/2

1/2

1/2

1 1/2 units reorganized into medium-size attack plane units.

Medium-size flying boat

1

1

[ ]

3

3

Large-size flying boat

1

1

(1)

(1)

1 (1)

2

"Research"

1/2

1/2

1

1/2

1/2

1 1/2

Total

3

2

6 1/2

1

2 1/2

1/2

1/2

1/2

1/2

17

3 1/2

3

1

1

1/2

1

1

1/2

[ ]

1/2

(1)

1

(1)

1/2 (1/2)

1/2

1/2 (1/2)

1

(1)

4

(4)

35

(4)

39

Note

1. 1/2 reconnaissance seaplane units each for Matsura and Chinoki [in] Old Program column was changed in Program No. 2 to 1/2 reconnaissance seaplane unit for Tatoyam and Kure.

2. 1/2 medium-size attack plane each for Omura, Ominate and Kanoya [in] Old Program column was changed from 1/2 small-size flying boat unit for Sasebo, Tateyama and Saoki after reorganization.

3. Numbers of units in parenthesis in Program No. 2 column indicated units not yet organized as of end of fiscal year 1936.

Navy Aeronautical Department, General Affairs Bureau, 2nd Section

1 September 1936

 

Japanese Monograph No. 149

OUTLINE OF NAVAL ARMAMENT AND PREPARATIONS FOR WAR

Part II

PREPARED BY MILITARY HISTORY SECTION HEADQUARTERS, ARMY FORCES FAR EAST

DISTRIBUTED BY OFFICE OF THE CHIEF OF MILITARY HISTORY DEPARTMENT OF THE ARMY

FOREWORD

This is the second of a series of six monographs in regard to Japan's naval armament in preparation for and during the Pacific War.

Additional monographs covering Japan's naval armament plans are:

Mono No

Outline of Naval Armament and Preparations for War, Part I

145

Outline of Naval Armament and Preparations for War, Part III

160

Outline of Naval Armament and Preparations for War, Part IV

169

Outline of Naval Armament and Preparations for War, Part V

172

Outline of Naval Armament and Preparations for War, Part VI

174

--iii--

Preface

Through Instructions No. 126 to the Japanese Government, 12 October 1945, subject: Institution for War Records Investigation, steps were initiated to exploit military historical records and official reports of the Japanese War Ministry and Japanese General Staff. Upon dissolution of the War Ministry and the Japanese General Staff, and the transfer of their former functions to the Demobilization Bureau, research and compilation continued and developed into a series of historical monographs.

The paucity of original orders, plans and unit journals, which are normally essential in the preparations of this type of record, most of which were lost or destroyed during field operations or bombing raids rendered the task of compilation most difficult) particularly distressing has been the complete lack of official strength reports, normal in AG or G3 records. However, while many of the important orders, plans and estimates have been reconstructed from memory and therefore are not textually identical with the originals, they are believed to be generally accurate and reliable.

Under the supervision of the Demobilization Bureau, the basic material contained in this monograph was compiled and written in Japanese by former officers, on duty in command and staff units within major units during the period of operations. Translation was effected through the facilities of Allied Translators and Interpreters Service, G2, General Headquarters, Far East Command.

This Japanese Operational Monograph was rewritten in English by the Japanese Research Division, Military History Section, General Headquarters, Far East Command and is based on the translation of the Japanese original. Editorial corrections were limited to those necessary for coherence and accuracy.

--v--

TABLE OF CONTENTS

Page

Chapter I

The Third Replenishment Plan

1

The Plan and Subsidiary Means Used to Replenish Naval Surface Strength

2

Air Strength Plan

7

Chapter II

Acceleration of War Preparations and Supplementary Armament Plans Caused by Outbreak of China Incident

11

Acceleration of War Preparations

11

Supplementary Armament Plan

14

Extraordinary Military Expenditure

16

The Fourth Replenishment Plan

17

Appendix I

Third Replenishment Plan

25

Ship Construction

25

Aircraft Preparation - Land-based

27

Aircraft Preparation - Land-based Air Group

27

Appendix II

Expected Air Strength at the Time of the Completion of the Third Replenishment Plan

29

Appendix III

Outline of the First War Preparations Analysis Conference

31

Appendix IV

Fourth Replenishment Plan of the Naval

34

Aircraft Preparation - Land-based Air Group

34

Shipboard Air Strength

35

Ship Construction

37

--vii--

TABLE OF CONTENTS (CONT'D)

Page

Chart No. 1

Approved Budget (Fiscal year 1937)

3

Chart No. 2

Ship Construction Progress of Third

6

Chart No. 3

Budget (Fiscal year 1939)

20

Chart No. 4

Ship Construction Progress of the Fourth

21

--viii--

Chapter I The Third Replenishment Plan

In December 1934, Japan submitted notification of the abrogation of the Washington Treaty. At the same time, after intensive research for the coming disarmament conference, it was found that Japan did not have the facilities, material or money to compete with the western powers in naval armament. It was planned, therefore, that in order to safeguard herself, Japan would stress the point of finding the common upper limit of naval strength and of reducing or entirely abolishing offensive vessels, such as battleships and aircraft carriers. It was felt that the naval ratio that had been adopted both in the Washington and London Treaties was unreasonable and would not guarantee the security of Japan.

The Naval Disarmament Conference of the five powers, Japan, Great Britain, United States, France and Italy was held in London in December 1935. Since Great Britain and the United States not only disagreed in principle with Japan's contention that the naval treaty was unreasonable, but ignored it, Japan withdrew from the conference in January 1936. Thus, with the expiration of both the Washington and First London Naval treaties, Japan was no longer committed to any treaty obligations with Britain and the United States.

These events combined to make Japan feel herself in an isolated position in regard to the Occidental powers. In addition, from the time of the establishment of Manchukuo the Chinese people had openly

--1--

shown their resentment against Japan, and, especially in North China, armed clashes were frequent. With the marked increase of clashes in Asia between Japan and China and between Japan and the Soviet Union, Japan began to feel pressure from all sides, which she believed would have to be overcome at any cost.

In March 1936, Great Britain requested the Japanese Government to take part in the limitation of guns on capital ships provided in the Second London Naval Treaty (British-American-French Naval Qualitative Limitations Treaty) but Japan declined the invitation. Since the end of 1935, in view of the unexpected delay in carrying out the Second Naval Replenishment Plan, Japanese naval authorities had been preparing for the next armament replenishment plan. As a result, the Third Replenishment Plan, extending over five years (four years in the case of aircraft) beginning in the 1937 fiscal year, was formulated. This plan called for a total of 66 ships (including two battleships) amounting to approximately 270,000 tons; also included in the plan were 14 new air units, bringing Japan's total air strength to 53 units. (See Appendix I) The approved budget for shipbuilding was approximately 800,000,000 yen. (3 1/2 yen = $1.00) (See Chart I) The progress of ship construction is shown in Chart 2.

The Plan and Subsidiary Means Used to Replenish Naval Surface Strength

This was the first plan made and put into effect by the Japanese Navy after it had been freed from obligations of international dis-

--2--

Chart — 1 Approved Budget (Fiscal year 1937)

Type of Ship

Tonnage

Number of Ships

Cost (in 1,000 yen)

Total (in 1,000 yen)

Battleships

35,000

2

98,000

196,000

Aircraft Carriers

24,500

2

80,850

161,700

Minelayer (Class A)

11,600

1

24,940

24,940

Minelayer (Class B)

5,400

1

9,750

9,750

Emergency Net Layers

2,000

2

4,500

9,000

Escort Ships

1,200

4

3,060

12,240

Gunboats (Class A)

1,000

2

3,300

6,600

Gunboats (Class B)

270

2

1,174.5

2,349

Destroyers

2,000

18

9,000

162,000

Submarines (Class A)

2,600

2

14,560

29,120

Submarines (Class B)

2,100

12

12,180

146,160

Minesweepers

600

6

2,130

12,780

Naval Transport

10,000

1

4,400

4,400

Survey Ship

1,600

1

3,760

3,760

Light Minelayers

700

5

2,450

12,250

Subchasers

300

9

2,450

13,500

Total

70

806,549

Budget Appropriation for Each Fiscal Year (in 1,000 yen)

Total

1937

1938

1939

1940

1941

806,549

48,007

206,342

232,392

229,057

90,751

In addition, on account of a rise in prices, a 57,669,038 yen increase was authorized for the fiscal year 1941.

--3--

armament treaties. Every effort was to be made to compensate for lack of quantity in naval strength by the improvement of quality. To do this, it was necessary to re-equip vessels in order to make each ship as effective as possible.

Battleships

Due to lack of facilities, materials and the time necessary for construction. and from the viewpoint of expense, it was realized that it would be impossible to raise the ratio of battleships. Therefore, as the Japanese Navy could not compete with the United States Navy in regard to the number of battleships, it was decided to construct the two largest and most effective battleships in the world, the Yamato and Musashi.

Since 1931, with each armament plan, the modernization of capital ships had been carried out. The conversion of the nominal training ship Hiei back to a battleship was begun in 1937, when the ship was freed from treaty limitations.

Aircraft Carriers

In view of the vulnerability of aircraft carriers, quantity rather than quality of carriers was given first consideration, and a policy was adopted whereby the ratio of Japanese aircraft carriers would be kept equal to, if not greater than, that of the United States.

It was considered that the two aircraft carriers of the Shokaku class, which had been included in the Third Replenishment Plan (See

--4--

Chart 2) would easily be able to balance the United States Navy in the number of carriers completed in accordance with the First Vinson Plan. However, since 1937 the United States had been planning an increase in aircraft carriers. It was also reported that the number of carriers to be constructed according to the Second and Third Vinson Plans would total between 8 and 10. It seemed therefore that, in spite of the Japanese plan to maintain parity with the United States, this would not be realised. Under the circumstances the Japanese Navy decided to conduct intensive research and investigation into the progress of the United States naval armament, and, if necessary, in order to obtain parity, to requisition and convert first-class merchant ships into aircraft carriers.

Cruisers

The Japanese Navy's most favorable ratio with the United States Navy, under treaty restrictions, was cruisers. Generally speaking, however, the number of Japanese cruisers could not exceed 70 percent of the United States cruisers. The Japanese Navy, therefore, adopted a policy of equipping each cruiser with as many guns and torpedoes as possible. Furthermore, with the removal of treaty restrictions, it was able by the end of the 1938 fiscal year to complete the Conversion of the light cruisers Mogami and Mikuma into heavy cruisers, by replacing 155mm guns with 200mm guns.

The light cruisers Kumamo and Suzuya, which were of the same type as the Mogami, and the Tone and Chikuma, which were based on the

--5--

Chart-2 Ship Construction Progress of Third Naval Replenishment Plan

Type

Period of Construction

Ships

Battleships

Nov 37 to Aug 42

Yamato Musashi

Carriers

Dec 37 to Sep 41

Shokaku Zuikaku

Seaplane tender

Nov 38 to Jan 42

Nisshin

Minelayer

Jul 39 to Oct 41

Tsugaru

Emergency Netlayer

Apr 38 to Jun 40

Hatsutake Aotaka

Escort Ships

Hot 38 to Mar 40

4 - Shimsihu Class

Gunboats (Class A)

Feb 39 to Apr 41

Hashidate Uji

Gunboats (Class B)

Aug 38 to May 40

Fushimi Sumida

Destroyers

Sap 37 to Jun 41

15 - Kagero Class

Submarines (Class A)

Jan 38 to Oct 41

1 - I-9 Class 1 - I-10 Class

Submarines (Class B)

Jan 38 to Oct 41

6 - I-15 Class

Submarines (Class C)

Aug 37 to Oct 41

5 - I-16 Class

Subchasers

Oct 37 to Aug 39

6 - No. 7 Class

Naval transports

Jul 39 to Jul 40

Kashino

Survey ship

Jan 40 to Jan 42

Tsukushi

Light Minelayer

Jun 37 to Oct 40

5 - Sokuten Class

Minesweepers

Oct 37 to Jun 39

9 - No. 4 Class

TOTAL: 66 ships, approximately 277,000 toss.

(Note) Construction of three destroyers and one submarine was cancelled in order to divert the funds to the construction of the two super-battleships, Musashi and Yamato

--6--

Second Replenishment Plan, were in the process of construction, so that they could be completed as heavy cruisers, without going through the process of conversion.

Thus, when the Second Replenishment Plan was fully carried out, the number of heavy cruisers in the Japanese Navy totalled eighteen. In spite of the fact that the Third Replenishment Plan did not include the construction of cruisers, it appeared that, as far as cruisers were concerned, the Japanese Navy would be able to maintain an almost equal strength with the United States Navy.

Air Strength Plan

Although the budget appropriation approved for the preparation of air strength of approximately 140,000,000 yen, reaching a total of about 200,000,000 yen by the addition of various other subsidiary expenditures, may appear small when compared with the 800,000,000 yen for shipbuilding scheduled in the Third Replenishment Plan, this was actually not so. The expenditure for the maintenance and replacement of 53 land-based air units and about 600 shipboard aircraft, when this plan was carried into effect, totalled an extraordinarily large amount. Moreover, with the rapid increase in air strength, airfields had to be constructed and expanded. Factories also were established under the administration of the Naval Aeronautical Department for the manufacture, maintenance and repair of aircraft equipment.

--7--

With the commencement of the Third Replenishment Plan, not only did the Naval Aeronautical Department become more and more important as a training control unit, but its duties as a repair and construction control organ brought it more closely in line with the Naval Technical Department. This situation resulted in subsequent approved budgets being almost equal for both organs.

Soon after the commencement of the Third Replenishment Plan, the China Incident broke out, so that the operational loss of naval aircraft showed a rapid increase, with the resultant difficulties in executing armament plans and activating forces. Measures were taken at this time to obtain unanimous approval of the Extraordinary Military Expenditure (See p. 16). Increase of industrial production was intensified with the expansion of the war front, and, in spite of the fact that it became necessary to increase various emergency armament and war preparations for the China Incident, their completion was successfully expedited. The bulk of the land-based air force (totalling 12 units excluding one unit of medium attack planes and one unit of medium flying boats) was completed by the end of the fiscal year 1938; the uncompleted unit of medium attack planes was completed within the fiscal year 1939 and the medium flying boats within the fiscal year 1940. The completion of shipboard strength was realised between 1938 and 1941 (except for aircraft for the Musashi which was completed in 1942) according to the time of completion of shipbuilding.

--8--

The grand total of air strength at the time of the completion of this plan was roughly estimated as shown in "Expected Air Strength at the Time of Completion of the Third Replenishment Plan" (See Appendix II) though it was subject to many additions and changes with the development of the China Incident.

The preparation of land air bases steadily progressed with the preparation of aircraft. Land-based air groups which were activated by the end of 1940 were as follows:

Name of Air Group

Date of Activation

Note

1

YOKOSUKA

1 Apr 1916

According to the Second Replenishment Plan

2

SASEBO

1 Apr 1918

3

KASUMIGAURA

1 Nov 1922

4

OMURA

1 Nov 1922

5

TATEYAMA

1 Jun 1930

6

KURE

1 Jun 1931

7

OMINATO

1 Nov 1933

8

SAEKI

5 Feb 1934

According to the Second Replenishment Plan

9

MAIZURU

1 Oct 1935

10

KISARAZU

1 Apr 1936

11

KANOYA

1 Apr 1936

12

CHINKAI

1 Oct 1936

13

YOKOHAMA

1 Oct 1936

--9--

14

TAKAO

1 Apr 1938

According to the Third Replenishment Plan

15

SUZUKA

1 Apr 1938

16

OITA

5 Dec 1938

17

TSUKUBA

5 Dec 1938

18

KASHIMA

5 Dec 1938

19

CHICHI JIMA

1 Apr 1939

20

USA

1 Oct 1939

21

CHITOSE

1 Oct 1939

22

YATABE

1 Deo 1939

23

HYAKURIHARA

1 Dec 1939

24

IWAKUNI

1 Dec 1939

25

TSUCHIURA

5 Nov 1940

26

MIHORO

1 Oct 1940

According to the

Fourth Replenishment Plan

27

GENZAN

1 Oct 1940

28

TOKO

1 Oct 1940

29

HAKATA

5 Not 1940

--10--

CHAPTER II

Acceleration of War Preparations and Supplementary Armament Plans Caused by Outbreak of China Incident

Acceleration of War Preparations: At the time of the outbreak of the China Incident in July 1937, the Third Replenishment Plan was already under way, and the subsidiary preparations to modernise existing ships and reorganize air groups were making steady progress. In order to prevent obstructing the execution of the armament program, the Japanese Government and the Navy desired to localise the Incident. However, the Incident spread to Central and South China, causing a general clash between Japan and China.

In early and middle July the Navy made preparations to cope with the situation (See Monograph No. 144; "Political Strategy prior to Outbreak of War," Part I, 1931-1939, Chapter II.) These preparations included:

a. Reorganisation of units and deployment of necessary strength for emergency to include the activation, preparations for deployment and alerting of two Special Combined Air Groups and a Special Naval Landing Force.

b. Drafting of necessary personnel.

c. Acceleration of manufacturing and stockpiling of equipment, war materials (especially materials impossible to import in wartime), bombs and machine gun ammunition.

--11--

d. Preparation for requisitioning necessary ships and complete equipment of navy vessels.

e. Establishment of necessary facilities for defense of key positions.

By the middle of August, the main results obtained from the above preparations were:

a. The Aoba and Kinugasa, having been repaired, were engaged in army transportation as guard ships.

b. The Belfast Maru, Kinugasa Maru and Choko Maru had been requisitioned.

c. The Asahi Maru had been requisitioned and converted into a hospital ship, while a special sick bay had been organized aboard the hospital ship Muroto.

d. The First Naval Harbor Master's Department had been established aboard the naval auxiliary ship Asahi, and this ship attached to the Third Fleet and used for salvage and repair.

e. The necessary facilities for the transportation of a Special Naval Landing Force to the Tsingtao area had been installed on the Settsu and Yakaze.

On 13 August 1937, the Chinese Army made an attack on a Japanese naval land combat unit at Shanghai, which precipitated the two armies into a full-scale war.

Believing that the Incident would continue to expand for a considerable time, and that friction with the Three Powers would necessarily increase during that period, the Navy determined to

--12--

accelerate war preparations immediately to cope with the situation. On 23 August, in order that the Chief of Navy General Staff might present his views to the Navy Minister, the First War Preparations Analysis Conference was held. (See Appendix III)

In spite of the capture of Nanking in November 1937, the China Incident dragged on, and cases of protest and interference by the Three Powers occurred so frequently that the execution of war preparations based on the conferences held on all such occasions between the Navy Ministry and the Navy General Staff became standard procedure. Moreover, preparations covering a long period were to be given priorities by weighing their importance with the existing and next armament plans, and by advancing their completion dates in the form of additional armament. Special emphasis was placed on:

Replenishment of aircraft lost in operations

Obtaining and training aircraft personnel

Completion of operational air bases and strengthening of their defenses

Gradual overhaul or modernization of all existing navy vessels

Gradual requisitioning and conversion of ships and construction of miscellaneous small ships

Procurement, increased production, storage and supply of required war materials

Strengthening of various land and sea facilities along with the completion of the above strength and equipment.

--13--

Supplementary Armament Plan

In order to achieve the objectives agreed upon by the Navy Ministry and the Navy General Staff, it became obvious that it would be necessary to execute an additional armament plan for the period between the Third and Fourth Replenishment Plans.

Ship Strength

In the fiscal year 1938, a budget appropriation of 17,200,000 yen for the construction of three ships — two training ships (three requested) and one storeship (two requested) — was approved as an expenditure extending to 1941. The construction of these ships was to be carried cut together with the Third Replenishment Plan.

The obsolete ships used for training had always been regarded as a disgrace and, with the sharp increase in the number of cadets, and the tremendous development in ships' equipment and tactics, it became absolutely necessary to replace them. The Katori and Kashima (displacement tonnage per ship 5,800 tons) were completed and commissioned as training ships in April and May 1940 respectively.

One storeship, the Irako (displacement tonnage, 9,570 tons) was completed and commissioned in December 1941. However, with the expansion of the area of fleet training and the extension of the training period, this one storeship was considered completely inadequate to cope with the situation.

--14--

Air Strength

The Navy General Staff requested 75 additional medium attack planes for the war with China within the fiscal year 1937. This meant almost doubling the existing strength of medium attack planes within half a year. Every effort was made to accelerate production by advancing to the utmost the date of completion of two and a half units of medium attack planes in accordance with the Third Replenishment Plan, completing three units of medium attack planes as an additional armament plan in 1938, and reinforcing the Kanoya and Takao Air Groups with the above units, thus expediting the replenishment of loss by the operational forces.

It required great effort to replenish and maintain air strength even in peacetime. It was, therefore, found extremely difficult to maintain combat strength by the prompt replenishment of losses in the China operations, and, at the same time, to plan the increase in strength demanded by the armament plan, For instance, the number of aircraft which was scheduled to be completed by the third year of the China Incident as a replenishment, or strengthening, of war preparations for the Incident, in addition to aircraft scheduled in the existing armament plan (excluding the above mentioned additional armament of three units of medium attack planes) was estimated as shown below:

--15--

Carrier Fighters

131

Carrier Bombers

57

Carrier Attack Planes

71

Reconnaissance Seaplanes

59

Medium Attack Planes

72

Heavy Attack Planes

0

Transports

0

Total

390

Needless to say, these figures indicated the budgetary strength which was estimated after considering the Extraordinary Military Expenditure appropriation, not the actual strength which was assigned and committed to the China operations. It is interesting to note that the actual number of aircraft completed in a year was much the same as the total number of aircraft scheduled in past armament plans covering several years.

Extraordinary Military Expenditure

With the outbreak of the China Incident, measures were taken to obtain unanimous approval of the Extraordinary Military Expenditure. This was done not only from the standpoint of urgency of operations and preservation of secrets, but it was also a very effective means of accelerating armament and war preparations.

In the past the expenditure of the budget had been restricted within narrow limits. The Extraordinary Military Expenditure made lt possible to divert money from one item or expenditure to

--16--

another or to expend it for a new item in accordance with changes in plans.

The Fourth Replenishment Plan

Soon after the outbreak of the China Incident, the Chinese Government submitted a protest to the League of Nations. The United States Government in October 1937, as though in concert with this action accused Japan of violating the Kellogg Pact. Anti-Japanese feeling in both Great Britain and the United States was aggravated at this time by the Panay and Lady Bird Incidents, caused in connection with the capture of Nanking. Although these incidents, themselves, were settled by diplomatic measures, with the expansion of operations in Central and South China, cases of violations of rights and interests, particularly of Great Britain and the United States, occurred so frequently that anti-Japanese feeling became increasingly evident. This, together with the acute situation in Europe, caused both Great Britain and the United States to greatly accelerate the strengthening of armament and war preparations.

The German-Austrian Anschluss and the German invasion and annexation of the Sudeten area, which were carried out in the spring and fall of 1938, seemed to be drawing Europe closer to a great cataclysm. World conditions caused Great Britain and France to place themselves on a quasi-wartime footing, and the United States to further step up armament and war preparations against the Axis Powers.

--17--

The armament of the United States Navy, according to the First Vinson Plan for the fiscal year 1934, was to be expanded to the limit permitted by the treaty. Moreover, a budget for an increase of 2 battleships, 20 destroyers, 6 submarines and 333 aircraft was approved in 1936. In addition, a plan for a huge amount of armament, totalling 81 vessels, was announced for the fiscal year 1937: 2 battleships, 3 aircraft carriers, 11 cruisers, 16 submarines, 48 destroyers and 1 gunboat. Besides this, a budget for the construction of two replacement battleships from the fiscal year 1939 onward was requested. Furthermore, in May 1938, the Second Vinson Plan, requiring 46 combat ships (including three battleships and two aircraft carriers), 26 auxiliary ships, 950 aircraft and one airship was signed by the President. The Second Vinson Plan was a ten-year plan. At the same time, a budget for about 1,100,000,000 dollars was passed for land and sea facilities.

In view of the United States increase in strength according to the plan for the fiscal year 1937, and the Second Vinson Plan, which was approximately four times that of the Third Replenishment Plan for the Japanese Navy, Japan, in spite of her difficulties in China, felt forced to cope with the situation at any cost by means of another armament plan.

The Japanese Navy was confronted with the absolute necessity of completing its armament, while on the other hand, operations on

--18--

the Chine mainland necessarily required priority of Army armament. This gave rise to a number of problems in regard to the financial and material limits of the country. In the meantime, the Navy Ministry and the Navy General Staff, upon investigating the contents of the two huge armament plans of the United States Navy, advanced the next armament plan, aiming at Japan's ship strength to at least equal one of the American plans, and her air strength to be on parity. They continued negotiations with the ministries concerned until at last in 1939 the budget passed the Diet. This was known as the Fourth Replenishment Plan of the Naval Armament Completion Plan for the fiscal year 1939. (See Appendix IV) An approved budget of approximately 1,200,000,000 yen was appropriated for the construction of 83 vessels (including two battleships). (See Chart 3) The progress of construction of these vessels is shown in Chart 4. In air strength, this plan called for 75 units as a nucleus comprising 34 1/2 operational units and 40 1/2 training units, both of which belonged to land-based air forces. About 300,000,000 yen was appropriated solely for the construction of aircraft. This plan was intended to cover six years (five years in the case of air strength) from the fiscal year 1939 to 1944.

The Third Naval Replenishment Plan aimed to double the naval air strength in five years, in spite of the fact that it had taken over 20 years to build it to its present strength. The Navy did

--19--

Chart — 3 Budget (Fiscal year 1939)

Type

Tonnage

Number

Cost (in 1,000 yen)

Total Cost (in 1,000 yen)

Battleships

40,000

2

130,000

260,000

Carrier

28,500

1

101,175

101,175

Cruisers (Class B)

6,600

4

26,400

105,600

Cruisers (Class C)

8,200

2

31,160

62,320

Destroyers (Class A)

2,100

18

10,605

190,890

Destroyers (Class B)

2,600

6

12,090

72,540

Cruising Submarines (Class A)

2,600

1

16,640

16,640

Cruising Submarines (Class B)

2,200

15

14,190

212,850

Submarines (Navy Large Type)

1,600

10

10,480

104,800

Training Ship

6,000

1

7,200

7,200

Seaplane tender

5,500

1

11,825

11,825

Light Minelayers

700

10

2,660

26,600

Mine sweepers

700

6

2,660

15,960

Subchasers

300

4

1,620

6,480

Emergency net layer

2,000

1

4,900

4,900

Oil tanker

5,000

1

6,000

6,000

Total

83

1,205,780

Annual Budgets (in 1,000 yen)

1939

1940

1941

1942

1943

1944

Total

60,150

119,250

289,785

384,184

290,080

62,330

1,205,780

These budgets were approved as general accounts. However, they were included in the extraordinary military expenditure after the fiscal year 1942.

--20--

Battleship 110

Apr 40 to Dec 40

Construction in progress

Dec 40 to Jun 42

Construction suspended

Jun 42 to Nov 44

Converted to carrier Shinano

Battleship 111

Nov 40 to Dec 40

Construction in progress

Dec 40 to Mar 43

Construction suspended

Mar 43

Dismantled

Carrier

Jul 41 to Mar 44

Taiho

Cruiser (Class B)

Jun 40 to Nov 44

4 Agano Class cruisers

Cruisers (Class C)

1939

1 ship - construction suspended.

Feb 41 to Feb 43

Oyodo

Destroyers (Class A)

May 39 to Jul 43

3 Kagero Class

12 Yugumo Class

1 Shimakaze

Destroyers (Class B)

Jul 40 to May 43

6 Akitsuki Class

Submarine (Class A)

Apr 40 to May 42

I-11 Class Submarine

Submarine (Class B)

Jun 39 to Apr 43

I-14 I-15 Class Submarines

Submarine (Navy Large Type)

Jun 40 to Aug 43

10 I-176 Class submarines

Training ship

Oct 39 to Jul 41

Kashii

Seaplane tender

Nov 40 to Apr 42

Akitsushima

Light Minelayer

Sep 39 to Jul 43

1 ship - construction suspended

9 Improved Sokuten Class

Subchaser

Jul 39 to Mar 41

4 No. 13 Class Subchasers

Minesweeper

Sep 40 to Mar 43

6 No. 19 Class Minesweepers

Emergency Netlayer

Dec 40 to Not 41

Wakataka

Tanker

Mar 42 to May 43

Sunosaki

Note: Although the budget approved by Diet showed a total of 83 ships to be constructed, the Navy decided to build only 80 ships and to use the extra appropriations to construct two super battleships. Later, it was found that this plan

not practical and Battleship 110 was converted into the Carrier Shinano, while, after suspending construction on Battleship 111 in December 1940, lt was finally dismantled in March 1943.

--21--

not have complete faith in this ambitious program, however, it was felt necessary to attempt this goal in order to instill the "air strength first" idea into the naval armament plan. About this time aircraft production had made unexpected progress as a result of the China Incident. Taking advantage of this momentum, this plan aimed at developing the low aircraft production capacity of Japan at any cost to carry out the Fourth Replenishment Plan. Therefore, subsequent to the commencement of this plan, it was made a rule to give priority to the naval air armament plan within the limits of scheduled manpower, materials and facilities. Accordingly, from that time forward, naval air armament was not restricted for financial reasons. The building up of air power, however, was retarded by the fact that, in spite of the vision of the few who could see the tremendous importance of air power, with many the basic idea of huge warships and big guns as a nucleus of sea power, with air power as auxiliary strength, still predominated.

With the Third Replenishment Plan almost completed, but before the Fourth Replenishment Plan was completely drafted, in October 1938, naval air armament under the Fourth Replenishment Plan was begun. The plan made unexpectedly good progress due to strong advocacy of "air strength first" in naval armament. Production facilities were expanded and aircraft production techniques were much improved.

--22--

When the situation became critical in August 1941, the order was given to advance the plan by one year, changing it to a four-year plan to be completed in the fiscal year 1942. Not only was this plan completed as revised, but, during this time, a large amount of the strength lost due to the China Incident was replaced. From 1941 onward, although each supplementary armament plan and each new armament plan was put into effect in advance, they were rarely completed in the specified time.

The number of aircraft completed in the fiscal years 1940 and 1941 to replace the expended aircraft was estimated to be:

Carrier fighters

75

Carrier bombers

37

Carrier attack planes

36

Reconnaissance seaplanes

43

Medium attack planes

102

Total

293

Thus, from a practical angle, the air strength of the Japanese Navy at the time of the outbreak of the Pacific War was almost equal to the expected strength at the time of the completion of the Fourth Replenishment Plan. Details of the plan in connection with other war preparations and armament plans will be mentioned in monograph No 160.

Compared with the preparation and replenishment of the above air groups, the expansion of aircraft production and the training of air personnel lagged far behind. The greatest difficulties encountered in air preparation and armament throughout the Pacific war, and even in pre-war days, were the poor aircraft equipment and the shortage of well-trained air personnel.

--23--

Appendix I

Third Replacement Plan

Ship Construction

Tonnage
per Ship
(Standard Displacement)

Number of
ships

Total Tonnage

Speed
(knots)

Cruising
Range

Principal Armament

Remarks

Battleships

64,000

2

120,000

27

16 knots

7,200 nautical miles

460mm guns

9

155mm guns

12

127mm Dual Purpose guns

12

Aircraft

6

Aircraft Carriers

20,000

2

60,000

34

18 knots

9,700 nautical miles

12.7mm Dual Purpose guns

16

Aircraft-96/Fighter/Primary

18

Fighter/Secondary

8

Bomber/Primary

54

Bomber/Secondary

18

Seaplane

Tender

9,500

1

9,500

22

16 knots

8,000 nautical miles

140mm guns

6

Originally planned for minelayers

Reconnaissance Seaplane Primary

20

Reconnaissance Seaplane Secondary

5

Facilities for boarding Type A
Midget Submarines

Minelayer

4,000

1

4,000

21

14 knots

6,400 nautical miles

127mm guns

4

Depth Charge Thrower

1

Mines

600

Minelayer (Emergency Net Layers)

1,600

2

3,200

20

14 knots

4,100 nautical miles

40mm Machine guns

2

Depth Charge Thrower

1

Antisubmarine Nets

24

Escort Ships

860

4

3,440

20

14 knots

8,000 nautical miles

120mm guns

3

Depth Charge Thrower

1

Gunboats (Class A)

990

2

1,980

19.5

14 knots

2,500 nautical miles

120mm Dual Purpose guns

3

Gunboats (Class B)

320

2

640

17

14 knots

1,400 nautical miles

Torpedo Tube

1

Destroyers

2,000

15

30,000

35

18 knots

5,000 nautical miles

120mm guns

6

The approved budget was for 18 vessels. The budget for three of them was diverted to battleship construction.

Torpedo Tubes

8

Submarines

(Class A)

2,200

2

4,400

Surface 23.5

16 knots

16,000 nautical miles

140mm gun

1

Torpedo Tubes

6

Aircraft

1

Submarines

(Class B)

1,950

6

11,700

Surface

23.6

16 knots

14,000 nautical miles

140mm gun

1

The approved budget was for 12 vessels. The budget for one of them was diverted to battleship construction.

Torpedo Tubes

6

Aircraft

1

Submarines

(Class c)

2,100

5

10,900

Surface

23.4

16 knots

,000 nautical miles

140mm gun

1

Torpedo Tubes

8

Minesweepers

630

6

3,700

20

14 knots

2,000 nautical miles

120mm guns

2

Depth Charge Throwers

2

Naval

Transport

10,360

1

10,360

14

14 knots

8,000 nautical miles

120mm Dual Purpose guns

(Equipped with facilities for the transportation of 460mm gun)

2

Survey ship

1,400

1

1,400

20

16 knots

8,000 nautical miles

120mm guns

4

Light

Minelayers

720

5

3,600

20

14 knots

2,000 nautical miles

80mm Dual Purpose guns

1

Depth Charge Throwers

2

Subchasers

290

9

2,610

20

14 knots

2,000 nautical miles

40mm Machine guns

TOTAL

66

269,510

--25--

Aircraft Preparation - Land-based Air Croup

Classification

Number of Units

Number of Aircraft

Total Number of Aircraft

Per Unit

Scheduled

Primary

Secondary

Primary

Secondary

Operational Air Group

Carrier Combers

1

12

4

12

4

16

Land Attack Planes

2.5

12

4

30

10

40

Reconnaissance Seaplanes

1.5

8

4

12

6

18

Medium Flying Boats

1

4

2

4

2

6

Total

6

58

22

80

Training Air Group

Primary

1

12

18

12

18

30

Intermediate

5

12

12

60

60

120

Combat Trainers

2

12

4

24

8

32

Total

8

96

86

182

GRAND TOTAL

14

154

108

262

NOTE: The total of 14 units in the above chart is some times regarded as included in the Third Replenishment Plan, because the completion of shipboard air groups mas delayed along with the progress of ship construction.

Shipboard Air Strength

Classification

Number of Aircraft

Total
Number of
Aircraft

Primary

Secondary

Carrier Fighters

48

12

60

Carrier Bombers

144

48

190

Reconnaissance Seaplanes (Ship board)

38

4

42

Total

230

64

294

NOTE: There was a budget appropriation for carrier bombers but for attack planes. This was a budget problem with the appearance of new carrier bombers.

--27--

Appendix II

Expected Air Strength at the Time of the Completion of the Third Replenishment Plan [two page table]

Aircraft type

Group

Operational air group

Plan

Former Plan (after reorganization)

First Plan

Second Plan

Third Plan

Total

Former Plan

(after reorganization)

First Plan

Classification of Number

Number of Units

Number of aircraft

Number of Units

Number of aircraft

Number of Units

Number of aircraft

Number of Units

Number of aircraft

Number of Units

Number of aircraft

Number of Units

Number of aircraft

Number of Units

Number of aircraft

Primary\ Auxiliary

Total

Primary\ Auxiliary

Total

Primary\ Auxiliary

Total

Primary\ Auxiliary

Total

Primary\ Auxiliary

Total

Primary\ Auxiliary

Total

Primary\ Auxiliary

Total.

Carrier fighters

1.5

18\6

24

1.0

12\4

16

2.5

30\10

40

5.0

60\20

80

0.58

6\2

8

1.0

12\4

16

Carrier bombers

1.0

12\4

16

1.0

12\4

16

Carrier attack planes

1.0

12\4

16

3.5

42\14

56

4.5

54\18

72

0.5

6\2

8

3.0

36\12

42

Carrier Reconnaissance planes

2.0

24\8

32

Medium attack planes

1.0

9\3

12

2.5

30\10

40

2.5

30\10

40

6.0

69\23

92

Large attack planes

1.5

12\3

15

12\3

15

Reconnaissance planes

2.5

20\10

30

1.0

8\4

12

1.5

5.0

40\20

60

2.0

16\8

24

Shipboard Reconnaissance Seaplanes (other than carriers)

Small flying boats

1.5

12\6

18

1.J

12\6

18

0.5

4\2

4

Medium flying boats

3.0

12\6

18

1.0

4\2

6

4.0

16\8

24

Large flying boats

1.0

2\0

2

1.0

2\0

2

2.0

4\0

4

Primary trainers

3.0

30\54

90

Intermediate trainers

Combat trainers

13\4

Research planes

1.0

4

16

0.5

8\2

8

Total

7.5

71\29

100

9.5

76\28

104

7.5

74\23

97

6.0

58\22

80

30.5

279\102

381

9.0

104\80

184

4.5

54\18

72

Armament Plan

Classification\Plan

Former Plan

First Plan

Second Plan

Third Plan

Total

Land-based operational air strength

100

104

97

80

381

Land-based training air strength

184

72

8

182

446

Carrier and shipboard air strength

510

284

294

1,088

Total

970

389

556

1,915

 

 

 

Land-based air group

Shipboard air strength

Grand Total

Training air group

Total

Second Plan

Third Plan

Total

Number of Units

Number of aircraft

Number of Units

Number of aircraft

Number of Units

Number of aircraft

Number of Units

Number of aircraft

Ships up to and in First Plan

Second Plan

Third Plan

Total

Primary\ Auxiliary

Total

Primary\ Auxiliary

Total

Primary\ Auxiliary

Total

Primary\ Auxiliary

Total

Primary\ Auxiliary

Total

Primary\ Auxiliary

Total

Primary\ Auxiliary

Total

Primary\ Auxiliary

Total

Primary

Auxiliary

Total

0.5

4\2

8

2.0

24\8

32

7.0

84\28

112

81\30

111

36\18

54

48\12

60

165\60

225

249

86

337

1.0

12\4

16

144\48

192

144\68

192

156

52

208

3.5

42\14

56

8.0

96\32

128

154\60

214

84\42

126

240\102

342

336

134

470

2.0

24\8

32

2.0

24\8

32

24

8

32

6.0

89\23

92

69

23

92

1.5

12\3

15

12

3

15

2.0

16\8

24

7.0

56\28

84

20\0

20

72\18

90

92\8

110

148

46

196

122\41

163

14\0

14

38\4

42

174\45

217

174

45

219

0.5

4\2

6

2.0

16\9

24

14

8

24

4.0

16\8

24

14

8

24

2.0

4\0

4

4

0

4

1.0

12\8

30

4.0

48\72

120

4.0

48\72

120

48

72

120

5.0

60\60

120

5.0

60\60

120

5.0

60\60

120

60

60

120

2.0

24\8

32

2.0

24\8

32

2.0

24\8

32

24

8

32

1.5

18\6

24

1 5

18\6

18

6

24

0.5

6\2

8

8.0

96\86

182

22.5

260\186

446

53.0

539\288

379\131

510

206\78

284

230\64

294

815\273

1,088

1,354

561

1,915

--29--

Appendix III

Outline of the First War Preparations Analysis Conference

23 August 1937

Matters for Consultation Concerning War Preparations

Arrangements and Explanations

Policy

In anticipation of the China operations being protracted, war preparations which are of direct necessity will be completed. In addition, part of the war preparations required for sea operations will be accelerated in order to brush off interference, if any, of the Three Powers.

Outline

Surface Units

The completion of the following ships being re-equipped or reinforced will be accelerated. Akagi, Yamashiro, Mogami, Submarine I-71

The re-equipment of ships which are slated to be completed by the end of 1937 will bo continued as scheduled. The re-equipment of four ships mentioned in the left column is slated to be completed in the first half of 1938, and the date of completion is set as the end of January 1938 with the exception of the Akagi, which requires special preparation in order to strengthen sea-air strength.

The construction of the following ships will be accelerated: Soryu, Tsurugizaki, Takasaki. Chitose. Subchasers and other ships nearing their completion in accordance with the Naval Replenishment Plan for the fiscal year 1937.

Besides the above, the existing surface units of the strength included in the war organisation plan for the fiscal year 1937 will be equipped so as to execute operations effectively.

Emphasis will be laid on the acceleration of preparation of ships under repair or under overhaul. However, obsolescent ships such as the Hirato, Yahagi and Karazaki are excluded from such preparation.

Necessary ships will be requisitioned.

Converted seaplane tenders 4; converted combined collier and oil tanker 1; converted

--31--

Converted aircraft carriers equipment and materials required for conversion work will be prepared for three ships of Asama Maru class.

gunboats 4; converted ships Ko 12; converted subchasers 4.

Motors to be used for operating lifts, the lifts themselves, other materials and blueprints for conversion plans.

Air Strength

Medium attack planes and their equipment. Manufacturing and completion of the above a according to Navy Secretariat Secret Document No 2893, will be accelerated to the utmost.

Other aircraft and their equipment. The losses of the existing strength will be replenished. Aircraft and its equipment will be completed to achieve strength on wartime footing for the fiscal year 1937.

Besides those now being assembled, 75 aircraft will be completed in 1937.

A monthly output of 120 aircraft is scheduled. It will be increased to 350 by the end of the fiscal year 1937.

Defense

It will be completed in accordance with the Secondary and the Tertiary Defense in the Essentials of Naval Defense Program for the fiscal year 1937.

Facilities

Air bases

Effort will be made to complete immediately air bases

under construction and other necessary facilities.

Communications facilities

Communications facilities necessary for the above-mentioned defense will be completed.

The air bases mentioned on the left will be established chiefly on South Sea Islands and the Kuriles. Places necessary to establish new air bases are Genzsan and Chitose (in Hokkaido).

To be established: Second Transmitting Station of Shanghai Land Combat Unit; Harbin Radio Receiving Substation; Rashin Communications Unit; Niigata

Radio Finder Station; Mikuriya Radio Direction Finder Station. Completion of Equipment for Communications Units.

Construction and repair facilities

Efforts will be made to complete facilities required for the prepara-

--32--

tion of above strength and of the Sixth Expeditionary Preparation Materiel.

Personnel

Efforts will be made to train the personnel required for the operation and maintenance of the above strength and facilities.

Personnel on First and Second Reserve Lists to be called to active service. Aircraft personnel to be trained.

Preparation of Expeditionary Materiel

Based on the above strength, preparations will be made for the completion of materiel for the opening of hostilities in accordance with the Expeditionary Preparations Regulations for the fiscal year 1937. Every effort will be made for the procurement and preparation of fuel, raw materials, bombs and other necessary arms.

Air defense equipment: Dual purpose guns; machine guns; range finders; sound locators.

Anti-Submarine equipment:

Mines; antisubmarine nets with mines; hydrophones.

Shells, powder and other equipment.

--33--

Appendix IV

Fourth Replenishment Plan of the Naval Armament Completion Plan Aircraft Preparation - Land-based Air Group

Classification

Operational air groups

Training air groups

Transport planes

Total

Number of Units

34.5

40.5

75

Number of aircraft

566

877

35

1,443 Plus 35

NOTE: If the strength of former plans is included, the total strength will amount to 128 units (2270 aircraft) 65 operational units (947 aircraft) and 63 training units (1323 aircraft) and 35 transports.

Details of this air strength are:

Classification

Number of Units

Number of aircraft

Per Unit

Total

Primary

Secondary

Total

Primary

Secondary

Total

Operation air group

Carrier fighters

6.5

12

4

16

78

26

104

Carrier attack alarms

2.0

12

4

16

24

8

32

Medium attack Planes

18.5

12

4

16

222

74

296

Reconnaissance seaplanes

7.5

8

4

12

60

30

90

Medium flying boats

Reorganized Two groups reduced

8

4

12

No increase or decrease in number

Large flying boats

Reorganized Two groups increased

8

4

12

28

16

44

Total

34.5

412

154

566

Training air group

Primary trainers

7.5

12

18

30

90

135

225

Intermediate trainers

15.5

12

12

24

186

186

372

Combat trainers

17.5

12

4

16

210

70

280

Total

40.5

486

391

877

Transport planes

Large transport planes

24

Medium transport planes

11

Total

35

GRAND TOTAL

75.0

898

545

1,443 Plus 35

--34---

NOTE: Approval was obtained to include the 3.0 medium attack plane units planned in the 1938 • Extraordinary Military Expenditure in the 18.5 medium attack plane units in this plan.

Subtracting 597 trainers from 1443 aircraft, there were 846 operational aircraft in all. This number corresponded to the number of navy aircraft in the Second Vinson Plan.

Shipboard Air Strength

Classification

Number of aircraft

Remarks

Primary

Secondary

Total

Carrier fighters

24

12

36

Carrier aircraft

Carrier bombers

24

12

36

"

Carrier attack planes

36

18

54

"

Reconnaissance seaplanes

48

0

48

Shipboard aircraft

Total

132

42

174

NOTE: The first completion expenditure for shipboard air strength is included in the ship budget in each armament plan.

It was planned to organise air groups at Komatsushima, Tainan, Misawa, Katori, Tokushima, Matsushima, Shinchiku, Mikawa Bay, Chitose and Genzan (as well as eight training air groups). However, the plan was to be changed as occasion demanded in accordance with the establishment of airfields, training programs or other situations that might arise.

--35--

Appendix IV(Cont'd)

Fourth Replenishment Plan of the Naval Armament Completion Plan - 1939

Ship Construction

Tonnage (Displacement

tonnage)

Number

Total Tonnage

Speed

(knots)

Cruising Range (knots-nautical miles)

Principal Armament

Note

Battleships

64,000

2

128,000

27.0

16-7,200

460mm guns

9

One ship's construction suspended and ship dismantled.

One a ship converted to carrier.

155mm guns

12

100m dual purpose guns

12

Aircraft

6

Carrier

30,360

1

30,360

33.3

18-10,000

100m dual purpose guns

6

Aircraft

52

Cruisers (Class B)

6,500

4

26,000

35.0

18-6,000

150mm guns

6

80mm dual purpose guns

4

Torpedo tube

8

Cruisers (Class C)

8,000

2

16,000

35.0

18-8,700

155mm guns

6

One ship's construction suspended

100m dual purpose guns

8

Destroyers (Class A)

2,000

16

32,000

35.0

18-5,000

127mm guns

6

The budget for 18 destroyers was approved, but the amount for the ten destroyers was diverted to the construction of super-battleships.

Torpedo tubes

8

Destroyers (Class B)

2,700

6

16,200

33.0

18-8,000

100m dual purpose guns

8

Torpedo tubes

4

Submarines (Class A)

2,200

1

2,200

Surface Speed

23.5

Surface Speed 16-16,000

140mm gun

1

Torpedo tubes

6

Aircraft

1

Submarines (Class B)

1,950

14

27,300

23.6

16-14,000

140mm gun

1

The budget for 15 submarines was approved, but the amount for one submarine was diverted to the construction of super-battleships.

Torpedo tubes

6

Aircraft

1

Submarine (Navy Large Type)

1,500

10

15,000

23.1

16-8,000

25mm machine guns

4

Torpedo tubes

6

Training ship

5,800

1

5,800

18.1

12-10,000

140mm gun

4

127m dual purpose guns

3

Flying boat tender

4,650

1

4,650

19.1

14-8,000

127mm dual purpose guns

4

(Facilities for landing 1 large type flying boat)

Minelayer

1,600

1

1,600

20.0

14-3,000

80mm dual purpose guns

2

Depth charge throwers

1

Light

minelayers

720

10

7,200

20.0

14-2,000

80mm dual purpose guns

1

Depth charge throwers

2

Minesweepers

630

6

3,780

20.0

14-2,000

120mm gun

1

Large minesweeping equipment

Subchasers

440

4

1,760

16.0

14-2,300

80mm dual purpose guns

1

Depth charge throwers

2

Oil tanker

4,460

1

4,460

18.0

14-9,000

120mm dual purpose guns

2

Gasoline supply equipment for an aircraft carrier at sea.

Total

60

322,310

--37--

 

Japanese Monograph No. 160

OUTLINE OF NAVAL ARMAMENT AND PREPARATIONS FOR WAR

Part III

PREPARED BY MILITARY HISTORY SECTION HEADQUARTERS, ARMY FORCES FAR EAST

DISTRIBUTED BY OFFICE OF THE CHIEF OF MILITARY HISTORY DEPARTMENT OF THE ARMY

This is the third of a series of six monographs in regard to Japan's naval armament in preparation for and during the Pacific War.

Additional monographs covering Japan's naval armament plans are:

Mono No

Outline of Naval Armament and Preparations for War, Part I

145

Outline of Naval Armament and Preparations for War, Part II

149

Outline of Naval Armament and Preparations for War, Part IV

169

Outline of Naval Armament and Preparations for War, Part V

172

Outline of Naval Armament and Preparations for War, Part VI

174

--iii--

Preface

Through Instructions No. 126 to the Japanese Government, 12 October 1945, subject: Institution for War Records Investigation, steps were initiated to exploit military historical records and official reports of the Japanese War Ministry and Japanese General Staff. Upon dissolution of the War Ministry and the Japanese General Staff, and the transfer of their former functions to the Demobilization Bureau, research and compilation continued and developed into a series of historical monographs.

The paucity of original orders, plans and unit journals, which are normally essential in the preparations of this type of record, most of which were lost or destroyed during field operations or bombing raids rendered the task of compilation most difficult; particularly distressing has been the complete lack of official strength reports, normal in AG or G3 records. However, while many of the important orders, plans and estimates have been reconstructed from memory and therefore are not textually identical with the originals, they are believed to be generally accurate and reliable.

Under the supervision of the Demobilization Bureau, the basic material contained in this monograph was compiled and written in Japanese by former officers, on duty in command and staff units within major units during the period of operations. Translation was effected through the facilities of Allied Translators and Interpreters Service, G2, General Headquarters, Far East Command.

This Japanese Operational Monograph was rewritten in English by the Japanese Research Division, Military History Section, General Headquarters, Far East Command and is based on the translation of the Japanese original. Editorial corrections were limited to those necessary for coherence and accuracy.

--v--

TABLE OF CONTENTS

Chapter

Page

I

GENERAL SITUATION

1

Preparation of Armament Against the United States

3

First Requisition, Conversion and Equipment of Vessels

6

Extraordinary Supplementary Armament Plan

7

Urgent Armament Plan

15

Second Requisition and Equipment of Vessels

29

Acceleration of other War Preparations

30

War Preparations Upon Decision to Go to War

31

Organization of Special Naval Units

32

Progress of Armament and Other War Preparations at the Time of the Outbreak of War

34

II

OUTLINE OF THE FIFTH AND SIXTH NAVAL ARMAMENT REPLENISHMENT PLANS

41

 

Charts

 

No. 1

Extraordinary Supplementary Armament Plan
Other Supplementary Armament Plans between

the Fourth Armament Replenishment Plan
and the Urgent Armament Plan

9

2

Progress of Shipbuilding

13

3

Urgent Armament Plan

17

4

Urgent Armament Plan Approved Budget

21

5

Urgent Armament Plan Progress of Shipbuilding

23

6

Air Strength at time of Outbreak of War

37

--vii--

7

Roster of Naval Officers at time of Outbreak of War

39

8

Fifth Armament Replenishment Plan

42

--viii--

Chapter I

General Situation

With the outbreak of World War II on 1 September 1939, the United States policy appeared to be to assist Great Britain and France in every way possible. The arms embargo was lifted at the beginning of November 1939, and, at the same time, the construction of an additional 40 US destroyers was approved. To offset the preponderance of German submarines in the spring of 1940, the United States leased 50 escort destroyers to Great Britain and extended positive aid in regard to the strengthening of the escort provided Europe-bound merchant ships.

In November 1939, having been notified of the commencement of the Japanese Fourth Armament Replenishment Plan, the United States Navy submitted to Congress the Third Vinson Plan, and, on 4 June 1940, it was signed by the President. The plan called for the construction of 3 aircraft carriers, 8 cruisers, 52 destroyers and 32 submarines, having a total tonnage of 400,000 tons. Also included in the plan was the construction of auxiliary vessels amounting to 125,000 tons, making a total tonnage of 525,000 tons. In addition, provision was made for 6,000 Navy planes and 36 flying boats. The appropriations for this plan amounted to $1,300,000,000, and the year of completion was set at 1944. It was estimated that the United States would have a main strength totaling more than 2,100, 000 tons, with a nucleus of 23 battleships, when this plan was completely realized.

--1--

In the spring of 1940, at the same time as the Third Vinson Plan began to get under way, the United States Navy decided to station permanently in the Hawaiian area the main force of the fleet then bound for that area to take part in large-scale maneuvers.

It was felt that the tightening of the political and economic encirclement of Japan by the United States, Great Britain, the Netherlands, Australia and China, coupled with the protraction of the China Incident, was making Japan's position more and more untenable. In order to surmount this difficulty, Japan took steps to strengthen her tripartite ties and to advance to the south. This caused the Anglo-American bloc to stiffen their attitude toward Japan. To cope with this critical situation, the Japanese Navy carried out various emergency measures. In 1941, to counteract the Third Vinson Plan, the Fifth Armament Replenishment Plan was adopted. (See Chapter II) However, on 19 June 1941, the astronomical United States' Stark Plan was approved. The Stark Plan was a two-ocean fleet plan with a 70 percent increase in the total tonnage of naval vessels and an increase in Navy planes to 15,000. The appropriation for this 6-year plan was $10,000,000,000.

Although it was realized that the fulfillment of the Fifth Armament Replenishment Plan would be most difficult from the standpoint of finance, materials and equipment, Japan considered it necessary to continue in the naval armament race, which resulted in the drafting of the Sixth Armament Replenishment Plan. (See Chapter II)

--2--

The strained relations between Japan and the United States led the navies of the two nations to compete in an unlimited and endless armament race.

Preparation of Armament Against the United States

The armament policy of the Japanese Navy had hitherto been based on the requirements of the national defense policy which aimed to maintain a strength in the ratio of 7:10 with the United States. The object of the national defense policy was to guarantee the security of the nation by securing the supremacy of sea and air in the Western Pacific. The 7:10 ratio was based on the tactical principle accepted at that time by the navies of all countries, which concluded that the strength of the offensive force must be at least 50 percent superior to that of the defensive force. While a navy of 7:10 ratio would be insufficient for offensive warfare, it would be enough for defensive warfare.

Because of the completion of the naval armament replenishment plans in the United States, the Japanese Navy's policy for maintaining the 7:10 ratio with the United States became futile, and it was estimated that in a short space of time the ratio of Japan's strength would decrease to less than 6:10 with the United States. Consequently, strenuous efforts were made to offset the quantitative deficiency by such means as effective armament preparations, skilled strategy and an effort to meet quantity with quality. Toward the end of 1940 Japan was forced to revise the armament policy generally as follows:

--3--

As it was predicted that in the near future the ratio of battleships would become less than 5:10 with the United States, the idea of meeting quantity with quantity was abandoned. It was decided that by building such huge battleships as the Musashi and Yamato quantitative deficiency would be balanced by the superior power of individual vessels. In accordance with the sudden change in the situation at the end of 1941, however, the construction of battleships, other than the almost completed Musashi and Yamato, was suspended. After the defeat in the Midway Battle in June 1942, it was decided to complete the reconstruction of the battleship Shinano into an aircraft carrier by the end of 1944.

Aircraft Carriers

Although at the end of 1940 there was no real difference in strength between the United States and Japan in regard to this type of vessel, there was every possibility that the United States would build more aircraft carriers in the near future. Therefore, without adhering to the tonnage ratio, Japan adopted a policy of creating parity on the number of vessels built by the United States. Finally, having exhausted her capacity for shipbuilding, Japan decided to convert first-class merchant ships into aircraft carriers. This plan was studied for some years before being put into operation. Cruisers

It was felt that there would be no difficulty in maintaining the 7:10 ratio with the United States in regard to cruisers, as

--4--

Japan was in quite a favorable position in regard to this type of vessel, especially in regard to heavy cruisers. It was decided, therefore, that the Japanese Navy policy of giving priority to superiority of fire power, torpedo power and speed should be continued.

Destroyers

Although the ratio with the United States in regard to destroyers was approximately 7:10, it was felt that within a short period of time the difference in strength would be great, because of the United States' gigantic armament plans, and her capacity to reduce the time required in shipbuilding. Another factor was that the Japanese Navy required their destroyers to carry heavy torpedo equipment to be used for night combat. This meant that the destroyers had to be larger, and, in consequence, not able to build as many.

Submarines

From the start, the quality and number of this type of vessel was not based on the ratio with the United States. As the Japanese Navy employed these vessels chiefly in interception actions and fleet warfare, they were all large, but they were few in number. In order to remedy this defect, midget submarines were built. Aircraft

Until the Third Armament Replenishment Plan, which counteracted the Second Vinson Plan, Japan aimed generally at an equal number of planes with the United States, but because no measure could be taken to cope with the Third Vinson Plan, which called for 6,000 Navy planes lost in the China Incident, it became more and more difficult

--5--

to maintain the ratio. By estimating the potential air strength of the United States which could be engaged in an offensive in the Far East, the minimum strength required to intercept this force was to be maintained. There was a tendency, however, to underestimate the power of the United States, and the Japanese Navy hoped that the lack of planes could be compensated by the mobility of the forces stationed at dispersed air bases.

First Requisition, Conversion and Equipment of Vessels

At the outbreak of the China Incident, vessels were requisitioned and equipped as part of the preparations for war. The Japanese Navy being unable to take any measures to counteract the Third Vinson Plan, decided on 15 November 1940 to requisition a total of 550,000 ship tons. These ships would be converted into aircraft carriers, transports, cruisers, gunboats and other auxiliary vessels as well as used as general naval transports. The work was undertaken gradually and, for the most part, was completed within six months.

In contrast to the nine aircraft carriers built under the Vinson Plans and supplementary armament plans, Japan's Third and Fourth Replenishment Plans made provisions for only three carriers. In consequence, in order to maintain parity, Japan had to make further plans. As a result, it was decided to convert first-class merchant ships. The Kasuga Maru was requisitioned and the Isumo Maru and Kashiwara Maru were purchased. The work of converting them into aircraft carriers was started in early 1941. The Taiyo (Kasuga Maru)

--6--

15,000 tons was completed 25 August 1941; the Junyo (Kashiwara Maru) 19,000 tons was completed 3 May 1942, and the Hiyo (Izumo Maru) 19,000 tons was completed 31 July 1942. It was planned that after careful study and preparation other merchant ships and some warships would be converted into aircraft carriers in order to increase the aircraft carrier strength.

In accordance with the Fourth Armament Replenishment Plan, the keels of the battleships Shinano and Kii were laid at Yokosuka and Kure Naval Yards respectively, and their construction up to double-bottoms was completed. The work was suspended temporarily on account of the delay in the construction of armour, and later, because of the major changes in armament and war preparation plans affected by the outbreak of war, it was decided to discontinue construction. Because of the sudden decrease in carrier strength caused by losses in the Battle of Midway, however, it became necessary to convert the Shinano into an aircraft carrier.

Extraordinary Supplementary Armament Plan

The Navy Ministry and the Naval General Staff agreed on the details of the Fifth Armament Replenishment Plan in order to counteract the Third Vinson Plan, but it looked as though there might be some difficulty in obtaining the necessary finances, materials and plants from the Finance Ministry, Planning Board and War Ministry respectively.

It was thought wise for the Naval General Staff to consult the Army General Staff in regard to the Fifth Armament Replenish-

--7--

ment Plan. The Army General Staff agreed to the plan under the following conditions: that it should be discussed again if it showed signs of hampering the established armament plan of the Army; that the Army would deliberate the matter of allocation of materials included in the material mobilization plan; and that it would decide the allocation of necessary manpower. Since the outbreak of the China Incident, the Japanese Navy had recognized the necessity for giving priority to the Army in regard to armament replenishments, in consideration of the nature of the operations. Unless priority was granted to the Fifth Replenishment Plan, however, it would be impossible to realize the plan. Therefore, the conditions imposed by the Array made it clear that they were rejecting the plan. From this time forward there was a constant struggle between the two services in regard to munition production.

The Japanese Navy felt keenly the necessity for taking extreme measures in order to accelerate their war preparations, and in May 1941 it established, and immediately put into execution, the Extraordinary Supplementary Armament Plan, known in Japanese as the "Maru Rin." (For details see Chart 1.)

Additional Supplementary Plans were placed into effect between the Fourth Armament Replenishment Plan and the Urgent Armament Plan and their progress, on the whole, was satisfactory. (See Charts 1 and 2)

There was no new plan for air armament. The air armament plan of the Fourth Armament Replenishment Plan had progressed compara-

--8--

Chart 1 - Extraordinary Supplementary Armament Plan

Standard Displacement per Vessel

Number of Vessels

Total Tonnage

Speed

Main Armament

Remarks

Submarines (Medium)

970

9

8,730

19.5 (Surface)

80mm gun

1

Approved budget the fiscal year 1941

General account: ¥196,424,750.00

25mm machine guns

2

Torpedo tubes

4

Submarines (Small)

525

9

4,725

14.2 (Surface)

25mm machine guns

2

Torpedo tubes

4

Gasoline tankers (Medium)

7,950

2

15,900

16.0

127mm gun

4

Gasoline tankers (Small)

4,460

4

17,840

16.0

120mm gun

2

Subchasers

440

16

7,040

16.0

80mm dual purpose gun

1

Auxiliary minesweepers

215

6

1,290

9.5

80mm gun

1

Approved budget the fiscal rear 1941

Extraordinary military expenditure: ¥21,030,000.00

Auxiliary minelayers

280

4

1,120

9.5

80mm gun

1

Refrigerator ships

920

3

2,760

14.0

80mm gun

1

Motor torpedo boats

20

4

120

35.0

25mm machine guns

2

Total

59

59,525

¥220,934,750.00

--9--

[--10-- blank]

Chart 1 - Other Supplementary Armament Plans between the fourth Armament Replenishment Plan and the Urgent Armament Plan

Standard Displacement per Vessel

Number of Vessels

Total

Speed

Main Armament

Remarks

Cable laying boats

1,564

4

6,256

14.0

80mm dual purpose gun

1

Approved budget the fiscal year 1939

Extraordinary military expenditure: ¥13,667,000.00 (of which ¥3,480,000.00 allotted to not or torpedo boats)

Refrigerator ship

920

1

920

14.0

80mm dual purpose gun

1

Refrigerator ship

640

1

640

13.0

80mm dual purpose gun

1

Suchasers

440

7

3,080

16.0

80am dual purpose gun

1

Approved budget the fiscal year 1940

Extraordinary military expenditure: ¥8,820,000.00

Training ship

5,800

1

5,800

18.0

140mm guns

4

Approved budget the fiscal year 1941

General account ¥7,660,000.00

127mm dual purpose guns

2

Torpedo tabes

4

--11--

[--12-- blank]

Chart 2 — Progress of Shipbuilding

Extraordinary Supplementary Armament Plan:

Type of Vessel

Class

Name of Vessel

Number of Vessels

Period of Construction

Remarks

Submarines (Medium)

Ro 35 Type

Ro 35 & others

9

Oct 41 to Dec 43

Submarines (Small)

Ro 100 Type

Ro 100 & others

9

Jun 41 to Apr 43

Gasoline tankers (med)

Ashizuri class

Ashizuri & others

2

Jul 41 to Nov 43

Gasoline tankers (small)

Sunozaki class

Takasaki

1

Jul 42 to Sep 43

Gasoline tankers (small)

Sunozaki class

3

Construction suspended

Subchasers

No 13 Type

No 24 & others

16

Hay 41 to Feb 43

Auxiliary Minesweepers

No 1 Type

No 1 & others

ft

Jun 41 to Oct 42

Auxiliary Minelayers

No 1 Type

No 1 & others

4

Jun 41 to Aug 42

Refrigerator ships

Kinozuki class

Hayasaki & others

3

Dec 41 to May 43

Motor Torpedo boat

No 1 Type

No 1 & others

6

Nov 41 to Dec 41

Total

59

56\3

May 41 to Dec 43

Completed

Other Supplementary Plans between the Fourth Armament Replenishment Plan and Urgent Armament Plan:

Type of Vessel

Class

Name of Vessel

Number of Vessels

Period of Construction

Remarks

Cablelayers

Kashima class

Kashima & others

4

Oct 39 to Aug 41

Refrigerator ships

Kinozaki class

Kinozaki & others

2

Oct 39 to Mar 41

Subchasers

No 13 Type

No 17 & others

7

Oct 40 to Nov 41

Training ship

Katori class

Yashiwara

1

Aug 41 to Oct 41

Construction suspended

Total

14

13\1

Oct 39 to Nov 41

Completed suspended

--13--

[--14-- blank]

tively well due to the stalemate in the China Incident with resulting small losses in aircraft. In addition, ¥100,000,000 was allotted for the immediate preparation and activation of 17 of the 93 units of the Training Air Group included in the Fifth Armament Replenishment Plan. (See Chart 8)

Urgent Armament Plan

At the liaison conference between Imperial General Headquarters and the Government, held on 2 July 1941, the "Outline of the National Policy of the Japanese Empire in connection with the Change of Circumstances," which emphasized the drive southward and the inevitability of war with the United States and Great Britain to achieve Japan's objective, was agreed upon. In order to comply with this policy, the Japanese Navy, being well aware of its great deficiency in armament as compared with the United States, realized that it was necessary to speed up war production. In the latter part of August 1941 it decided on the over-all execution of the Expeditionary Preparation Plan. As part of it, the Wartime Armament Preparation Plan was immediately enforced. This plan became known as the Urgent Armament Plan. (See Charts 3, 4 and 5)

In order to equip oil tankers to carry airplanes, an additional ¥10,264,000 was approved for 1944 (¥2,566,000 for each vessel). Because it was decided to construct an aircraft carrier of 12,500 tons instead of a cruiser, a further ¥10,610,000 was approved for 1945.

--15--

Chart 3 - Urgent Armament Plan

Type of Vessel

Number of Vessels

Total Tonnage
(Standard Displacement)

Speed

Main Equipment

Remark

Aircraft carrier

1

17,150

34

127mm dual purpose guns

12

UNRYU

25mm machine guns

31

Aircraft

49

Cruisers

2

24,400

35

200mm guns

10

After launching one cruiser converted into aircraft carrier (IBUKI Class), but conversion work suspended. Construction of 1 cruiser suspended.

127mm dual purpose guns

8

Torpedo tubes

14

Aircraft

3

Destroyers (Class A)

16

41,104

35

127mm guns

6

Construction of 8 destroyers suspended.

Torpedo tubes

8

Destroyers (Class B)

10

27,000

33

100mm dual purpose guns

8

Construction of 1 destroyer suspended.

Construction of 3 destroyers cancelled.

Torpedo tubes

4

Submarines (Class B)

6

13,110

Surface 23.6

140mm gun

1

Torpedo tubes

4

Aircraft

1

Submarines
(Class C)

6

13,060

Surface 23.6

140mm gun

1

Construction of 3 submarines cancelled.

Torpedo tubes

8

Submarines
(Medium)

12

11,412

Surface 19.7

80mm guns

1

Construction of 4 submarines cancelled.

Torpedo tubes

4

Submarines
(Small)

9

4,662

Surface 14.2

25mm machine guns

2

Torpedo tubes

4

Seaplane tender

1

4,620

19

127mm dual purpose guns

4

Construction suspended.

(Installation for carrying one large flying boat)

--17--

[--18-- blank]

Urgent Armament Plan (Cont'd)

Type of Vessel

Number of
Vessels

Total
Tonnage
(Standard
Displacement)

Speed

Main Equipment

Remark

Escort ships (Class B)

16

15,040

19.7

127mm dual purpose gun

1

120mm dual purpose gun

1

Depth charge throwers

2

Escort ships (Class A)

14

12,040

19.7

120mm guns

3

Depth charge thrower

1

Minesweepers

28

18,200

20

120mm guns

3

Construction of 17 minesweepers cancelled.

Large sweep cables

6

Auxiliary

16

3,360

95

80mm gun

1

Light minelayers

14

10,080

20

80mm dual purpose gun

1

Construction of 13 minelayers cancelled.

Depth charge throwers

2

Subchasers

20

8,800

16

80mm dual purpose gun

1

Construction of 1 subchaser cancelled.

Depth charge throwers

2

Auxiliary subchasers (wooden)

100

13,000

11

13mm machine gun

1

Motor Torpedo boats

18

1,350

29.5

Torpedoes

12

Construction of 3 torpedo boats suspended.

Construction of 7 torpedo boats cancelled.

Oil tanker

1

18,850

Construction cancelled.

Oil tanker

2

36,800

16.5

120mm dual purpose gun

3

Later equipped to carry 6 airplanes.

Oil tanker

1

6,000

Construction cancelled.

Total

293

300,058

--19--

[--20-- blank]

Chart 4 — Urgent Armament Plan

Approved Budget

Type of Vessels

Tonnage

Number
of Vessels

Cost of one
Vessel

(Unit of
¥1,000)

Total
Cost

(Unit of
¥1,000)

Cruisers

12,000

2

60,000.0

120,000.0

Aircraft Carrier

17,100

1

87,039.0

87,039.0

Destroyers (Class A)

2,570

16

17,424.6

278,793.6

Destroyers (Class B)

2,980

10

17,820.4

178,204.0

Submarines (Class B)

2,280

12

20,497.2

245,966.4

Submarines (Medium)

1,000

12

7,920.0

95,040.0

Submarines (Small)

550

9

4,713.5

42,421.5

Flying Boat Tender

11,00

1

47,410.0

47,410.0

Escorts

1,200

30

5,112.0

153,360.0

Light Minelayers

720

14

4,334.4

60,681.6

Minesweepers

700

28

3,738.0

104,664.0

Auxiliary
Minesweepers
(Fishing Boat Type)

300

16

1,431.0

22,896.0

Subchasers

400

20

2,921.6

58,432.0

Auxiliary

Subchasers

(Wooden)

100

100

780.0

78,000.0

Oil Tankers

18,400

4

14,720.0

58,880.0

Motor Torpedo Boats

100

18

2,262.0

40,716.0

Total

293

1,672,504.1

--21--

[--22-- blank]

Chart 5 - Urgent Armament Plan

Progress of Shipbuilding

Type of Vessel

Class

Name of Vessel

Number of Vessels

Period of
Construction

Remarks

(Total)

293

228

Completed

7

Dec 41 to Apr 45

Work suspended

58

Construction cancelled

Cruisers

Suzuka class

Ibuki

2

1

Apr 42 to Mar 45
(Converted into aircraft carrier)

Work for conversion into aircraft carrier suspended

1

Jun 42 to Sep 42
(suspended)

Work suspended

Aircraft carrier

Remodeled Hiryu class

Unryu

1

Aug 42 to Aug 44

Seaplane tender

Akitsushima class

Chihaya

1

Jul 42 to Oct 42
(suspended)

Work suspended

Oil tanker

Kazahaya class

Kazahaya and others

4

2

Oct 42 to Apr 44

(Large)

1

Construction suspended

(Small)

1

Construction cancelled

Escort ships (class A)

Remodeled Shimushu class

Etorofu and others

14

Feb 42 to Feb 44

Escort ships (class B)

Mikura-class Ukuru-class

Mikura & others

16

Oct 42 to Nov 44

--23--

[--24-- blank]

Chart 5 - Urgent Armament Plan (Cont'd)

Type of Vessel

Class

Name of Vessel

Number of Vessels

Period of

Construction

Remarks

Destroyers(class A)

Yugumo class

Hayanami & others

16

8

Jan 42 to May 44

Yugumo class

8

Construction cancelled

Destroyers (Class B)

Akitsuki class

Shimotsuki & others

6

Jul 42 to Apr 45

Akitsuki class

Mitsutsuki & others

1

Jan 44 to Mar 44
(suspended)

Work suspended

Akitsuki class

Kiyotsuki & others

3

Construction cancelled

Submarine (Class B)

Type I-15

I-40 and others

6

Mar 42 to Feb 44

Submarine (Class C)

Type I-16

I-46 and others

6

3

Dec 42 to Aug 44

Type I-16

I-49 and others

3

Construction cancelled

Submarine (Medium)

Type Ro-35

Ro 44 and others

12

8

Feb 42 to Sep 44

Type Ro-35

Ro 51 and others

4

Construction cancelled

Submarine (Small)

Type Ro-100

Ro 109 and others

9

May 42 to Jan 44

Minesweepers

Type No 19

No 25 and others

28

11

Apr 42 to Jul 44

Type No 19

No 31 and others

17

Construction cancelled

--25--

[--26-- blank]

Chart 5 — Urgent Armament Plan (Cont'd)

Type of Vessel

Class

Name of Vessel

Number of Vessels

Period of Construction

Remarks

Subchasers

Type No 13

No 40 and others

20

19

Feb 42 to Jul 44

Type No 13

No 59

1

Construction cancelled

Light minelayers

Remodeled Hirashima class

Ajiro

14

1

Sep 43 to Jul 44

Ajiro class

Kamishima & others

13

Construction cancelled

Auxiliary minelayers

Type No 1

No 7 and others

16

Feb 42 to Oct 44

Auxiliary subchasers

Type No 1

No 1 and others

100

Dee 41 to Mar 44

Motor torpedo boats

Type A

No 10 and others

18

8

Jul 42 to Feb 45

Type No 10

No 18 and others

3

Mar 44 to Jun 44
(suspended)

Work suspended

Type No 10

No 21 and others

7

Construction cancelled

--27--

[--28-- blank]

as only three, months had elapsed since a part of the Fifth Armament Replenishment Plan (air section) had been put into effect, and that only after long deliberation and preparation, it was considered impossible to establish another supplementary plan to further augment air strength without causing confusion. As the Fourth Armament Replenishment Plan was progressing smoothly, it was decided to advance the date of completion of this plan by one year, the plan to be completed by the end of the 1942 fiscal year instead of 1943. The remarkable success of the Japanese Navy Air Force at the beginning of the Pacific War, and the idea of giving priority to air armament which resulted from the above decision, not only enabled the general completion of the Fourth Armament Replenishment Plan within the prescribed time, but also led to the realization of the Revised Fifth Armament Replenishment Plan.

Second Requisition and Equipment of Vessels

The vessels obtained through the First Requisition were almost completely equipped and were steadily being added to the fleet strength. Under the firm policy adopted in the summer of 1941, it was decided that an additional 600,000 tons of vessels would be requisitioned for use as converted vessels or for increasing the number of supply and transport vessels.

Included in the vessels requisitioned in accordance with this plan was the Nitta Maru, which was converted into the aircraft carrier Chuyo, and such ships as the Aikoku Maru and the Hokoku Maru, which later distinguished themselves as converted cruisers

--29--

raiding merchant shipping. Most of these vessels were completely equipped by the end of 1941, but, because it was to be used to carry the mission dispatched for the conference between President Roosevelt and Premier Konoye at Juneau, Alaska, the equipping of the Nitta Maru was not started until June 1942. It was completed as the converted aircraft carrier Chuyo (15,000 tons) in the latter part of November 1942.

Acceleration of Other War Preparations

The activation of the wartime organization of the Imperial Japanese Navy was proclaimed on 1 September 1941, and the Fleet rose to unprecedented strength.

Following this, all vessels were subject to necessary repair before going into action. It was scheduled that, because of the state of emergency, this work would be completed by the end of November. The greatest problem in connection with the execution of the Expeditionary Preparation Plan was the lack of war materiel. The war materiel stockpile planned during peacetime was virtually nothing compared to the quantity required by the huge number of. units organized and for the vessels to be constructed under this plan. There was available only 10 to 30 percent of the required quantity of such materiel as large bombs, Type 91 torpedoes, 20mm. machine guns and ammunition, all of which were vital to air war. Moreover, as the output of these items was very slow, it was believed that, within several months after the outbreak of war, stockpiles would be completely exhausted. Consequently, efforts

--30--

were made by the Navy Ship and Ordnance Department to increase the production of large bombs by converting shells of 16-inch guns, aircraft torpedoes and machine guns. At the same time, in order to increase the production of the Navy's weapons, and also to produce the strength called for in the Fifth Armament Replenishment Plan, preparations were made for the establishment of a number of Navy plants.

Although it was planned that the facilities for producing Type 93 torpedoes for surface vessels would be converted into those for Hype 91 torpedoes for aircraft, such a conversion required a complete change-over of materials, parts, machinery, etc. As no plans had been made during peacetime for this change-over, it was expected that there would be a blank period of several months before the increased production of Type 91 torpedoes could be achieved. However, this precaution prevented the disruption of supplies in regard to air operations after the outbreak of war.

War Preparations Upon Decision to Go to War

At the conference in the Imperial Presence held on 5 November 1941, a decision was reached on the "Outline for the Execution of the National Policy of the Empire," the main point of which was "to continue negotiations with the United States, but, in case no accord can be reached, a resolution to declare war will be adopted and preparations for operations will be undertaken. If a diplomatic settlement cannot be reached by the beginning of December, the decision to declare war will be made immediately."

--51--

As a result of this decision, actual responsibility concerning Navy war preparations was shifted from the naval administration authorities to the Supreme Command. In preparation for the unprecedented operations against the United States and Great Britain, the strongest and wealthiest nations in the world, in a theater covering almost the entire Pacific area, the Navy Ministry and all sections in charge of construction, repairs, replenishment and supply had to make all-out efforts under conditions of top secrecy.

With the launching of the United States' Stark Plan, Japan intended to set up the Sixth Armament Replenishment Plan. Just when the problem of how to adjust this plan with the Fifth Armament Replenishment Plan was being studied, the decision to declare war was reached. The Japanese Navy, therefore, ordered the construction of 32 submarines and one bombing target ship to be included in the Fifth Armament Replenishment Plan. At the same time, they ordered the increased production of both operational and training aircraft.

It was decided that an additional 500,000 tons of vessels, including the Yawata Maru, would be requisitioned for the purpose of supplementing the lack of all types of ships. Work was begun on the Yawata Maru in January 1942, and toward the end of May it was completed as the converted aircraft carrier Unyo (15,000 tons).

Organization of Special Naval Units Construction Battalions

Eight construction units were organized for the purpose of

--32--

constructing airfields in occupied territories. The plan was to dispatch five units to the Philippines, two to the Fourth Fleet area (Inner South Seas Area) and one to the Malay area. Regular

officers had no experience in this type of work. The units, therefore, were composed mostly of nonmilitary men who were compelled to carry a large amount of equipment with them. It was extremely difficult under the circumstances to conduct preparations and transportation at a top secret level. A meeting to discuss the duties of the leaders was delayed until after 10 November, and the men were dispatched toward the end of the month in order to join their assigned units in time for the operations.

Special Landing Units

Two units were organized and trained in each naval district. They were assigned to the respective invasion forces and dispatched rapidly.

The airborne units which were being trained in the Tateyama Sector under the command of the Yokosuka Natal District were the first of their kind in Japan. They were well trained and on 20 November were assigned to the Combined Fleet.

Fuel Exploitation Unit

As it was presumed that all oil refining facilities would be destroyed by the authorities in the Dutch East Indies, the 101st Naval Fuel Depot was established for the purpose of restoring such facilities speedily and effecting the greatest output in production. It was planned to send this unit to Dutch Borneo simultaneously

--33--

with the occupation of that area. As a large quantity of machinery was necessary and technical aid from commercial firms was required, it was especially difficult to maintain secrecy with this project.

Other Units

Preparation for the dispatch of fire-fighting units for oil fields, personnel for military post offices and weather units was undertaken simultaneously. No great difficulty was encountered with these units.

On 5 November 1941, the Chief of the Naval General Staff issued directives to all naval operational forces to commence defensive preparations in conformity with plans regarding their deployment. All surface units strove for the early completion of the planned emergency war preparations and all Naval Districts made efforts to intensify security patrols by organizing garrison units, comprised of members of the former naval barracks.

Progress of Armament and Other War Preparations at the Time of the Outbreak of War

Prior to the outbreak of war, successive supplementary armament and other war preparations had been undertaken and their completion had been accelerated to the utmost. The resultant progress in ship construction at the time of the outbreak of war on 8 December 1941 was generally as shown below. In addition, the Fourth Armament Replenishment Plan was almost completed and such preparations as the requisitioning and completion of converted vessels, strengthening of ground and port defenses, and procurement and

--31--

transportation of equipment and the necessary war materials were in progress.

Number of Ships at the Time of the Outbreak of War

Battleships

10

301,400 tons

Aircraft Carriers

10

152,970 tons

Heavy Cruisers

18

158,800 tons

Light Cruisers

20

98,855 tons

Destroyers

112

165,868 tons

Submarines

65

97,900 tons

Others

156

490,384 tons

Total

1,466,177 tons

Ships under construction

Battleships

2

128,000 tons

Aircraft Carriers

4

77,860 tons

Light Cruisers

4

42,700 tons

Destroyers

12

27,120 tons

Submarines

29

42,554 tons

Others

37

57,225 tons

Total

88

375,459 tons

Requisitioned Vessels

By the middle of 1940, the vessels requisitioned for the purpose, of continuing the China Incident amounted to 200,000 tons. At the end of 1940 it was decided to requisition an additional 1,650,000 ship tons and to continue to convert these vessels until the outbreak of war. At the time of the outbreak of war, the state of these vessels was:

Completely equipped converted vessels

522

approximately 1,150,000 tons

Converted vessels being equipped

41

approximately 170,000 tons

Vessels to be converted or equipped

180

approximately 290,000 tons

--35--

Requisitioned vessels which would not be converted

approximately 200,000 tons

Total

approximately 1,810,000 tons

Air Strength

Details of air strength at the time of the outbreak of war are shown on Chart 6.

Naval Personnel

The number of naval personnel at the time of the outbreak of war was as shown hereunder:

Active Service

Recalled

Reserve

Total

Officers

10,000

506

1,338

11,844

Special Duty Officers

2,997

775

3,772

Warrant Officers

5,262

3,415

8,677

Petty Officers and men

238,235

60,312

298,547

Total

65,008

1,338

322,840

The number of officers, according to their rank and branch of service, is shown on Chart 7.

--36--

Chart 6 — Air Strength at time of Outbreak of War

Details

Operational
Air
Group

Training
Air
Group

Shipborne

Total

Outer
Combat
Force

Inner
Combat
Force

O*

R*

O

R

O

R

O

R

O

R

Fighters

Interceptors

180

51

36

12

50

31

149

10

415

104

Night fighters

Carrier bombers

9

5

36

12

38

19

135

3

218

39

Carrier attack planes

6

2

42

14

165

189

9

402

108

Land reconnaissance planes

18

6

18

6

Land bombers

Land attack planes

255

84

80

20

4

2

339

106

Patrol planes

Transports

38

38

Fighter

2-seater reconnaissance seaplanes

10

4

28

14

24

12

99

12

161

41

3-seater reconnaissance seaplanes

16

7

28

16

40

20

74

11

158

54

Submarine reconnaissance planes

Flying boats

36

12

13

5

49

17

Land trainers

286

286

286

286

Sea plane trainers

94

94

94

94

Utility

84

84

84

84

Total

568

171

263

785

631

646

45

2262

940

O - Operational R - Reserve

--37--

Chart 7 — Roster of Naval Officers at Time of Outbreak of War

LINE

ENGINEER

PAYMASTER

MEDICAL

PHARMACY

SHIPBUILDING

ENGINE MANUFACTURING

ORDNANCE MANUFACTURING

TOTAL

TOTAL

Active

Recall

Reserve

Active

Recall

Reserve

Active

Recall

Active

Recall

Active

Active

Active

Active

Active

Recall

Reserve

Admiral

11

11

11

Vice-Admiral

62

4

3

3

2

1

1

72

4

76

Rear-Admiral

151

21

16

18

5

1

8

199

21

220

Captain

492

232

185

11

84

12

73

15

13

49

911

255

1,166

Commander

695

26

316

2

112

2

90

4

22

13

35

1,287

30

1,317

Lt Commander

720

33

12

338

4

112

2

208

27

7

19

13

52

1,469

66

12

1,547

Lieutenant

887

8

275

338

1

77

263

2

382

112

14

38

36

170

2,126

125

352

2,603

Lt (Jr Grade)

455

1

461

144

115

427

468

29

55

122

288

1,988

7

576

2,571

Ensign

636

240

157

158

62

45

8

14

49

244

1,215

398

1,613

Midshipman

440

96

47

6

30

101

720

720

Total

4,549

325

988

1,574

18

350

1,126

18

1,287

145

62

176

278

948

10,000

506

1,338

11,844

--39--

Chapter II

Outline of the fifth and Sixth Naval Armament Replenishment Plans

The Fifth Naval Armament Replenishment Plan was deliberated with the object of counteracting the Third Vinson Plan, but, in consideration of the huge scale of the Third Vinson Plan, and the fact that the United States had been adopting supplementary plans each year, calling for considerable strength, it was impossible for Japan, from the standpoint of her economic and industrial power, to establish a plan to counteract these plans. The Japanese Navy studied the situation carefully during 1940, and finally an understanding was reached between the Navy Ministry and the Navy General Staff around May 1941, to execute a plan starting from simple and prepared armament. At the same time, it was decided that, in regard to the budget, formal steps would be taken later. Details of the strength of vessels and air armament included in armament preparations requested in a preliminary discussion between the Navy Ministry and the Navy General Staff are shown in Chart 8.

The Navy Ministry studied these requests and decided that, in view of the budget, the materials on hand and the production facilities available, the plan for ship construction should be a 9-year plan starting in 1942 and ending in 1950. The necessary expenditure was estimated at ¥4,400,000,000 (¥4-$1). Although it was difficult to estimate the completion date of the air armament program, it was believed that it would require a shorter period

--41--

Chart 8 — Fifth Armament Replenishment Plan

Vessel strength requested

Battleships (Yamato-Class)

3

Super cruisers (new Type)

2

Aircraft carriers (Taiho Class)

3

Seaplane tenders

2

Flying boat tender (Large)

1

Flying boat tenders (Small)

6

Cruisers (Medium)

5

Cruisers (Light)

4

Submarine tenders

2

Minelayers

2

Netlayer

1

Destroyers (Class A)

16

Destroyers (Class B)

16

Submarines (Class A)

2

Submarines (Class B)

12

Submarines (Medium)

9

Submarines (Small)

9

Submarines (Navy Type large)

10

Submarines (Supply)

3

Gunboat (Large)

1

Gunboats (Small)

2

Escort ships (Class A)

4

Minesweepers

10

Subchasers

18

Light minelayers

8

Naval auxiliaries (Transport)

3

Naval auxiliary (Survey)

1

Naval auxiliary (Provision)

1

Naval auxiliary (Icebreaker)

1

Naval auxiliaries (Repair)

2

Total

159

650,000 tons

--42--

Chart 8 - Air strength requested (cont'd) Operational Air Group

Type of aircraft

Number of Units

Number of aircraft

Land fighters

14

336

Fighter-bombers

10

240

Land reconnaissance planes

2

48

Fighter seaplanes

12

288

Bomber seaplanes

2.5

40

Flying boats (Medium)

10

120

Flying boats (Large)

8

96

Patrol planes

6.5

104

Transports

2

48

Total

67 units

1,320

The grand total at the time of completion was 132 units.

Fifth Armament Replenishment Plan (Cont'd)

Training Air Group

Type of aircraft

Number of Units

Number of aircraft

Land trainers

10

240

Seaplane trainers

9.5

228

Utility trainers

21.5

516

Land combat planes (Small)

22.5

608

Combat seaplanes (Small)

11

198

Land combat planes (Medium)

10.5

252

Combat seaplanes (Medium)

8

96

Total

93

2,138

The grand total at the time of completion was 156 units.

--43--

of time than the ship program. The estimated amount required for the air armament program was ¥2,000,000,000.

As a tremendous amount of expansion would be required in both land and sea installations to cope with this program, ¥1,900, 000,000 was set aside for installations for increasing production capacity and ¥500,000,000 for training installations.

In order to achieve this objective, it was necessary for naval armament preparations to receive priorities in regard to securing personnel and materials, and the Army was asked to make concessions in this regard.

In accordance with the above, the Navy Ministry decided to convert two of the three Taiho-class aircraft carriers into Hiryu-class vessels and to support the over-all plan of the Navy General Staff.

In July 1941, just when various plans were gradually taking shape after the basic plan of the Fifth Armament Replenishment Plan was informally decided, the United States suddenly announced the Stark Plan, with its astronomical naval armament plans. This clearly demonstrated the United States' determination to dominate the seas. The plan was a great shock to the Japanese Navy and a quick counter-plan was sought. The Navy Ministry and the Navy General Staff conferred in regard to the over-all adjustment of the Fifth and Sixth Armament Replenishment Plans, and, toward the end of October, the Navy General Staff formally presented the Fifth and Sixth Armament Replenishment Plans simultaneously to the Navy Ministry. The Navy Ministry replied that utmost efforts would be

--44--

made for the execution of both plans in accordance with the decision to declare war, although nothing definite could be said about the Sixth Armament Replenishment Plan. In the meantime, air armament and the completion of 32 submarines of the Fifth Replenishment Plan would be undertaken, while other armament preparations contained in the same plan would be conducted after the budget of the following fiscal year was approved.

Immediately after the outbreak of the Pacific War, successive war preparation projects were undertaken. Japan was faced with a basic revision of the ratio between air and sea strength. Equipment of large ships called for in the ship plan was suspended and efforts were concentrated on small vessels and local strength. The Fifth Armament Replenishment Plan was first changed to the Revised Fifth Armament Replenishment Plan and later to the Third Stage Revised Armament Production Plan. The details of this revision are given in Monograph No 169, "Situation from Outbreak of War to Revised Fifth Armament Naval Armament Replenishment Plan."

The strength requested by the Navy General Staff of the Navy Ministry for the Sixth Armament Replenishment Plan was:

Ship strength: 197 vessels totaling approximately 800,000 tons, including 4 battleships, 4 super cruisers, 3 aircraft carriers, 12 cruisers, 34 destroyers and 67 submarines.

Air strength: 68 operational air groups (making a total of 200 groups after completion.)

Despite the fact that nothing definite was established in regard to such matters as the budget, because details of strength

--45--

had not been decided, the Navy Ministry acknowledged the Sixth Armament Replenishment Plan. When war broke out, however, through battle experiences, a complete revision of plans for shipbuilding was brought about and the Sixth Armament Replenishment Plan ended as a mere paper plan.

As a condition of going to war, the Navy requested 1,450,000 tons of steel (including the priority allotment of secondary materials) and received an allotment of 1,100,000 tons as compared to the Army's 700,000 tons. This was tantamount to national priority being granted to naval armament preparation, and greatly contributed to the acceleration of naval armament in preparation for war.

--46--

Japanese Monograph No. 169

OUTLINE OF NAVAL ARMAMENT AND PREPARATIONS FOR WAR

Part IV

PREPARED BY

MILITARY HISTORY SECTION

HEADQUARTERS, ARMY FORCES FAR EAST

DISTRIBUTED BY

OFFICE OF THE CHIEF OF MILITARY HISTORY

DEPARTMENT OF THE ARMY

FOREWORD

This is the fourth of a series of six monographs in regard to Japan's naval armament in preparation for and during the Pacific War.

Additional monographs covering Japan's naval armament plans are:

Mono No

Outline of Naval Armament and Preparations for War, Part I

145

Outline of Naval Armament and Preparations for War, Part II

149

Outline of Naval Armament and Preparations for War, Part III

160

Outline of Naval Armament and Preparations for War, Part V

172

Outline of Naval Armament and Preparations for War, Part VI

174

26 July 1952

--iii--

PREFACE

Through Instructions No. 126 to the Japanese Government, 12 October 1945, subject: Institution for War Records Investigation, steps were initiated to exploit military historical records and official reports of the Japanese War Ministry and Japanese General Staff. Upon dissolution of the War Ministry and the Japanese General Staff, and the transfer of their former functions to the Demobilization Bureau, research and compilation continued and developed into a series of historical monographs.

The paucity of original orders, plans and unit Journals, which are normally essential in the preparations of this type of record, most of which were lost or destroyed during field operations or bombing raids rendered the task of compilation most difficult; particularly distressing has been the complete lack of official strength reports, normal in AG or G3 records. However, while many of the important orders, plans and estimates have been reconstructed from memory and therefore are not textually identical with the originals, they are believed to be generally accurate and reliable.

Under the supervision of the Demobilization Bureau, the basic material contained in this monograph was compiled and written in Japanese by former officers, on duty in command and staff units within major units during the period of operations. Translation was effected through the facilities of Allied Translators

--v--

and Interpreters Service, G2, General Headquarters, Far East Command.

This Japanese Operational Monograph was rewritten in English by the Japanese Research Division, Military History Section, General Headquarters, Far East Command and is based on the translation of the Japanese original. Editorial corrections were limited to those necessary for coherence and accuracy.

--vi--

TABLE OF CONTENTS

Page

Chapter I

Situation from Outbreak of War to Revised Fifth Naval Armament Replenishment Plan

1

General Situation

1

Air Armament

1

Combat Air Groups

2

Training Air Groups

3

Transport Planes

4

Shipborne Planes

5

Air Personnel

5

Emergency War Production Expediting Department

5

Battleship Construction Stipulated in Fourth Plan

7

Increase of Aircraft Carriers

13

Chapter II

Revision of Fifth Naval Armament Replenishment Plan (Revised Fifth Plan)

19

Progress of Revised Fifth Plan

20

Ship Strength

20

Air Strength

30

Supplementary Adjustments to Revised Fifth Plan

41

Supplementary Ship Construction Plan to Revised Fifth Plan

42

Appendix I

Naval General Staff Secret No 191

49

Appendix II

Official Reply from the Ministry of Navy: Secretariat Secret Document No 9599-2

51

--vii--

Charts

Page

Chart No 1

Rearrangement of Titles of Plans

9

Chart No 2

Status of Plans

10

Chart No 3

Program for Expediting War Preparations

11

Chart No 4

Flan for Increasing Aircraft Carriers

15

Chart No 5

Shipbuilding Plan

21

Chart No 6

Approved Extraordinary Military Appropriations for Fiscal Year 1943

25

Chart No 7

Status of Naval Vessels in the Scheduled Shipbuilding Plan End of June 1942

29

Chart No 8

Detailed Status of Shipbuilding Plan End of June 1942

31

Chart No 9

Results' of Ship Construction Under the Revised Fifth Plan

35

Chart No 10

The Air Strength Increase Plan for Fiscal Year 1942 (Combat air group) (Shipborne air strength) (Training air group)

37

Chart No 11

Ships to be Completed End of Fiscal Year 1944

45

Chart No 12

Ships to be Completed End of Fiscal Year 1945

46

Chart No 13

Approved Budget and Actual Results Achieved 1944

47

--viii--

CHAPTER I

Situation from Outbreak of War to Revised Fifth Naval

Armament Replenishment Plan

General Situation

The smooth progress of operations in the initial phase of the Pacific War led those in charge of the departments for war production to believe that the policy pertaining to such production was adequate. Later this was proven wrong and it became necessary to revise and strengthen methods of maintaining and stockpiling munition supplies. During this period, despite the fact that the Air Force played a vital part in the naval action off the Malayan coast, little attention was given to implementation of air armament or to the building up of the air force. The optimistic attitude of the time also led to delay in general national mobilisation, especially student mobilization for flight personnel.

As the lack of merchant shipping during the past few years had been held due to the expansion of naval armament, it was felt that in order to achieve the most effective results, the control of all shipbuilding should be under one head — the Navy Ministry. This was done soon after the outbreak of war.

Air Armament

In early February 1942, as it appeared that the Fourth Naval

--1--

Armament Replenishment Plan would be completed on time and the Fifth Naval Armament Replenishment Plan was moving forward smoothly, it was decided to regard the two plans as one from the beginning of the 1942 fiscal year.

The combat air groups, totalling 132 groups, were to be completed in five years according to previous plans and reorganization of air units was to be effected. Wartime strength was to be twice the planned peacetime strength.

A plan for training 156 air groups was to be completed in five years and the reorganization of the air units accomplished. Also, a total of 457 transport planes were to be prepared and maintained.

Combat Air Groups

The strength of combat air groups was to be more than double that of the Fourth Naval Armament Replenishment Plan and the plane complement aimed at approximately triple that of the Fourth Plan. An over-all change of air unit organization was to be made.

The reorganization of the Fourth Plan called for 65 groups with 1,032 aircraft as a normal complement and a reserve of 344, totalling 1,376 planes.

Reinforcements were to be 67 groups with 990 aircraft as a normal complement and a reserve of 330, totalling 1,320 planes.

The strength at the completion of the Fifth Plan would, therefore, be 132 groups with 2,022 aircraft as a normal complement and 674 as a reserve, totalling 2,696 aircraft. These air-

--2--

craft were to comprise:

Type of Aircraft

Number
of
Group

Number
of
Aircraft

Fighter

22

528

Fighter and bomber

13

312

Land reconnaissance plane

2

48

Medium land attack plane

15

360

Large land attack plane

10

240

Seaplane fighter

12

288

Seaplane bomber

9

144

Medium flying boat

12

144

Large flying boat

12

144

Patrol plane

8

128

Carrier fighter

3.5

84

Carrier attack plane

5.5

132

Reconnaissance seaplane

6

96

Large transport plane

2

48

Total

132

2,696

Training Air Groups

It was decided that the strength of the training air groups would be approximately two and a half times that stipulated in the Fourth Plan.

Up to the Fourth Plan 63 groups were completed with 894 aircraft as a normal complement and 639 as a reserve, totalling 1,533.

Reinforcements were to be 93 groups, comprising 1,270 aircraft as a normal complement and 848 as a reserve, totalling 2,118.

--3--

The total number of training air groups was to be 156, with 2,184 as a normal complement and 1,487 as a reserve, totalling 3,671 aircraft. This was to include 37 combat aircraft units to be reorganized.

The strength at the time of the completion of the Fifth Plan was to be:

Type of Aircraft

Number
of
Group

Number
of
Aircraft

Land training planes

30

720

Training seaplanes

16.5

396

Utility trainers

26.5

636

Small land combat planes

45.5

1,229

Medium land combat planes

10.5

252

Small combat seaplanes

19

342

Medium combat seaplanes

8

96

Grand total

156

3,671

Transport Planes

In consideration of the lessons learned from the China Incident and with the increase in land-based air strength, the necessity for a tremendous increase in the number of transport planes was recognized. A plan was formulated to prepare and maintain 457 aircraft by the end of 1946, comprising the following:

Large land aircraft

176

Large seaplanes

114

Small aircraft

167

Total

457

--4--

Shipborne Planes

A gradual increase in shipborne planes to 1,584, in accordance with the completion of vessels, was planned.

Air Personnel

The plan called for 31,578 pilots — 10% officers, 40% special and warrant officers and 50% non-commissioned officers. Ordnance maintenance personnel was to total 10,013, including 250 officers, and aircraft maintenance personnel 35,078, including 1,335 officers,

Emergency War Production Expediting Department

Hitherto, the supervision of war production had been actually the responsibility of the section chiefs and their subordinate officers, but with the imminence of war it was felt that the chiefs of the bureaus and departments should, themselves, assume responsibility for the stepping up of production of vital war materials. The War Preparations Examination Department had been established for this purpose but it was a committee-type organization which drew up plans rather than executed them. Consequently, the Emergency War Production Expediting Department was established in November 1941 to supervise the execution of these plans. Headed by the Vice Minister of the Navy, its members comprised the chief of each bureau of the Navy Ministry, and of such departments as the Technical, Aeronautical and Civil Engineering, as well as the First (Operation) and Second (War Preparation) Bureau of the Naval General Staff. The Chief of the First Section of the Naval Affairs

--5--

Bureau was appointed secretary of the department.

Meetings were held weekly and extraordinary meetings were called whenever the occasion demanded. Reports were submitted on the actual progress of war production and explanations given of future plans.

The Emergency War Production Expediting Department functioned efficiently for the entire duration of the war as a center of war production activities.

The Emergency War Production Expediting Department first drew up a plan for expediting war production. This covered a period to March 1944, and every means available was used to complete the required armament and other war materiel requirements by that time.

During the second period - from April 1944 onward - special study was made on the execution of plans for the anticipated Revised Fifth Plan and various supplementary amendments were completed and successively decided and enforced.

With the decision to execute plans for expediting war preparations during the first and second period, the relationship with the various past armament and war production plans became extremely complicated and it was feared that confusion would be created in the various enforcing headquarters concerning the titles of these plans. In order, therefore, to rearrange and standardize these titles, the Chief of the Naval Affairs Bureau issued the following notification soon after the outbreak of the war:

--6--

Naval Affairs 1, Top Secret Document No 79

2 February 1942

From: Chief of the Naval Affairs Bureau, Navy Ministry

To: Chiefs of All Bureaus Concerned in Navy Ministry

Chief of Naval Technical Department

Chief of Naval Aeronautical Department

Chief of Naval Civil Engineering Department

Chief of the 1st and 2d Bureau of the Naval General Staff

Chiefs of Staff of All Naval Districts

Chiefs of Staff of All Guard Districts

Notification Regarding Rearrangement of the Title of the Execution Plans for Expediting War Preparations.

An order has been issued to start the first period execution plan for expediting war preparations. As to the second period execution plan, it has also been decided that all quarters concerned should pursue its study. In recognition of the fact that the relationship of these plans with the existing plans for war preparations have become fairly complicated, we beg to inform you that it has been decided the titles of all plans are to be rearranged and standardised henceforth as shown in the attached table (See Charts 1, 2 and 3).

Battleship Construction Stipulated in Fourth Plan

The following program for the construction of two battleships specified in the Fourth Plan was approved by the Navy Minister on 1 April 1939.

Temporary Name

Place of Construction

To be Started

To be Completed

No. 110 Warship Yamato-type

Yokosuka Navy Yard

Early April of 1940

Late March of 1945

No. 111 Warship Yamato-type

Kure Navy Yard

Early May 1941

Late October of 1945

--7--

The construction of No. 110 warship was initiated on 4 April 1940 as scheduled, and No. 111 warship on 7 November 1940, six months earlier than scheduled. The construction work on No. 110 was started with great enthusiasm as the project was the first of its kind in Yokosuka Navy Yard since the completion of the battleship Mutsu in 1921. In late 1940, soon after the keel had been laid, the work was delayed for approximately three months because of the design which called for reinforcement of the double bottoms under the engine compartments. Early in 1941 the progress of construction of these battleships was slowed down and finally ceased. The main reasons for this were the necessity to prepare existing large ships for battle, insufficient production of armor plates, and arguments on the advisability of continuing construction on battleships whose vulnerability was revealed by the battle lessons in the initial phase of the war. However, since considerable progress had already been made on the framework of No. 110 at Yokosuka Navy Yard, and its dismantlement would have been very difficult, it was decided to continue construction on this ship. Both navy yards, however, were confronted with the difficult task of meeting urgent war requirements and were unable to continue construction work on the battleships. After the Battle of Midway it was decided to convert No. 110 warship into an aircraft carrier.

As construction of No. 111 warship at the Kure Navy Yard had been started six months later than No. 110 warship, work had not progressed so far and it was considered possible to dismantle it.

--8--

Chart No 1

Rearrangement of Titles of Plans

Plan

Existing Abbreviations

Readjusted
Abbreviation

Classification of War Expediting Execution

Plan for fiscal year 1939

Fourth

Fourth

Plan for the first period

execution of expediting war preparations. Abbreviated as "War Expediting, First".

Supplementary temporary military appropriations for fiscal year 1941

Extraordinary

Wartime, First

Maritime shipbuilding program for fiscal year 1941

Urgent

Supplementary appropriations advanced from fifth Plan

Supplement

(March 1944)

Plans for fiscal year

Fifth

Wartime, Second

Plan for the second period execution of expediting war preparations. Abbreviated as "War Expediting Second".

+ A

Supplement

to Fifth

- B

Deletion from Fifth

A and B will be decided by the request of the Naval General Staff

Remarks

War Expediting, First = Wartime, First + Bulk of remainder of Fourth 4 + Advanced preparation of Fifth

(Note) Wartime, First = Extraordinary + Urgent + Supplement

War Expediting, Second = Wartime, Second + Discontinued or suspended part of Fourth + Remainder of Wartime, First

(Note) Wartime, Second = Fifth + A - B

(B contains the advanced preparation of Fifth to War Expediting, First)

--9--

Chart No 2

Status of Plans

--10--

Chart No 3

Program for Expediting War Preparations

--11--

This was done after the Battle of Midway.

Increase of Aircraft Carriers

The Fifth Plan had a relatively smooth start, but, as a result of the Battle of Midway, an immediate and basic change in the plan became necessary. Four aircraft carriers (the main strength of the naval air forces) had been lost. To cope with this situation, the Naval General Staff immediately initiated a study to change the basic policy of armament and war production having the increase of air strength and the construction of aircraft carriers as its main objectives. The Naval Technical Department drafted a plan for the immediate construction of aircraft carriers which it submitted to the Bureau of Naval Affairs and the Naval General Staff. It was later approved by the Ministry of the Navy. This plan, which was confirmed on 30 June 1942, was known as the Navy Secretariat Secret Document No. 8107.

The plan called for the conversion into aircraft carriers, as soon as possible of the Izumo Maru, Nitta Maru and Taigei Maru which were scheduled for completion during 1942. During 1943, the Argentina Maru, Scharnhorst, 2 seaplane tenders and the Brazil Maru were to be converted into aircraft carriers. A study was ordered on the replacement and use of destroyer engines for the Brazil Maru, however, the ship was sunk in August 1942, before work could be begun on it.

--13--

The actual dates of completion were:

Name of Ship

Scheduled
Date
of
Completion

Actual
Date
of
Completion

HIYO (IZUMO Maru)

31 Jul 42

31 Jul 42

CHUYO (NITTA Maru)

End of Nov 42

25 Nov 42

RYUHO (Submarine Tender TAIGEI)

End of Oct 42

30 Nov 42

KAIYO (ARGENTINA Maru)

End of Jul 43

23 Nov 43

SHINYO (SCHARNHORST)

End of Jul 43

15 Dec 43

CHITOSE (Seaplane Tender)

End of Aug 43

1 Jan 44

CHIYODA (Seaplane Tender)

End of Dec 43

31 Oct 43

BRAZIL Maru

(Plan was dropped)

No. 110 warship was to be converted into an aircraft carrier and work to be accelerated so that it would be completed by December 1944.

The construction of fourteen (14) Hiryu-type ships, including the No. 302 warship, and six (6) No. 130 warship-type ships, including the No. 130 warship, was to be accelerated to the utmost degree. (See Chart 4.)

In regard to equipping aircraft carriers, a study was ordered to be made to simplify equipment as much as possible, and any improvements learned from battle lessons were to be applied, as long as they did not delay the period of completion.

--14--

Chart No 4

Plan for Increasing Aircraft Carriers

Type of ship

Fiscal year

1942

1943

1944

1945

1946

1947

1948

HIRYU type

3

5

4

2

No. 130 warship type

1

1

2

2

Converted ships

3

1 (No. 110 warship)

Total

3

5

5

5

5

4

2

Remarks

A. Those under consideration are not included.

B. This plan may be changed in the future.

--15--

In accordance with the above-mentioned plan ships to be newly built are shown according to their types in the following table:

Classification

Type or Name of Ships

Number of Ships

Number of ships According to Fifth Plan

Remarks

Under the new shipbuilding plan

No. 302 type (HIRYU Type)

4

1

Six ships ware included under the initial plan, but ad a result of the decision to convert No. 101 warship late an aircraft carrier, two ships allocated to the Yokosuka Navy Yard were cancelled, reducing the total to four ships.

Improved Type (improved type of HIRYU)

9

0

Improved Type 130 (improved type of TAIHO)

5

2

Total

18

3

Under the existing shipbuilding plan

No. 110 warship (SHINANO)

1

Conversion of a battleship from Fourth Plan

No. 130 warship (TAIHO)

1

Fourth Plan

No. 302 warship (UNRYU)

1

Urgent Plan

Total

Grand Total

21

Chart No 4 (cont'd)

Classification

Name of Ship

Scheduled
Date
of
Completion

Date
of
Completion

Remarks

New Warships

SHINANO (No. 110 Warship)

End of Dec 44

19 Nov 44

TAIHO (No. 130 Warship)

End of Jun 44

7 Mar 44

UNRYU (No. 302 Warship)

End of Sep 44

6 Aug 44

AMAGI (No. 302 Type)

End of Dec 44

10 Aug 44

KUTSURAGI (No. 302 Type)

End of Mar 45

15 Oct 44

KASAGI (No. 302 Type)

End of Jun 45

(Unfinished 34%)

Launched on 19 October 1944.

Work suspension order issued on 1 Apr 1945.

ASO (No. 302 Type)

End of Sep 43

(Unfinished 60%)

Launched on 1 November 1944.

Work suspension order issued on 9 November 1944.

IKOMA (Improved Type)

End of Oct 45

(Unfinished 60%)

Work suspension order issued on 9 November 1944.

1944

Disposed of 17 November 1944.

Improved Type, 8 ships

(Building suspended)

Improved No. 130 Type, 5 ships

(ditto)

Chart No 4 (cont'd)

--17--

A special study was also ordered to be made of the problem of converting commercial ships into aircraft carriers for transporting aircraft. At the same time three ships of the Asama Maru class were to be converted into aircraft carriers, employing destroyer engines.

It was decided that shipbuilding and conversion work, in accordance with this plan, would be undertaken by the Yokosuka and Kure Navy Yards, as well as by the Kawasaki and Mitsubishi-Nagasaki Shipyards and that the manufacture of the required armor plates, elevators, windscreens, cranes etc. would be effected as emergency measures.

Emergency aircraft construction work progressed smoothly until the middle of 1943. After that, however, the sudden increase in urgent repair work on damaged ships, and the scarcity of materials and labor hindered this shipbuilding plan.

--18--

CHAPTER II

Revision of Fifth Naval Armament Replenishment Plan

(Revised Fifth Plan)

After the Battle of Midway, the Naval General Staff immediately revised the previously decided armament plan and the Fifth Plan. The main points of the new plan were:

Air strength was to be increased rapidly. The 132 units scheduled in the Fifth Plan were to be increased to 347, an increase of 215, and 100 units above the maximum wartime strength of 232 units authorised by the Fifth Plan.

The number of aircraft carriers was to be increased immediately with the strength based on the Navy Secretariat Secret Document No. 8107.

More than 100 submarines were to be built and such forces as escorts, subchasers and other small anti-submarine ships were to be immediately increased.

The building of battleships and cruisers according to the Fourth Plan and Urgent Plan was to be suspended with the exception of the No. 110 warship which was to be converted into the aircraft carrier Shinano.

Front-line air bases were to be expanded and organized as quickly as possible against probable U. S. attacks.

Details of the plan were set forth in a formal request forwarded by the Chief of the Naval General Staff to the Minister of

--19--

the Navy. This request was known as Naval General Staff Secret Document No. 191 dated 30 June 1942. (See Appendix I.)

The official reply from the Ministry of the Navy on 3 August 1942, known as Secretariat Secret Document No. 9599-2 approving the plan and giving details of priorities to be followed is shown in Appendix II.

Progress of Revised Fifth Plan

Ship Strength

The Revised Fifth Plan, incorporating an enormous expansion in aircraft carriers, was an unprecedentedly large scale plan involving 361 ships with total tonnage of 1,156,061 tons. The shipbuilding plan and approved Extraordinary Military Appropriations for the fiscal year 1943 are shown on Charts 5 and 6. Furthermore, the prearranged work on naval vessels which the Naval Technical Department had on hand at the start of this plan (the end of June 1942), namely, the number of vessels called for in the earlier plan, which had not yet been completed, amounted to 410, as shown on Chart 7. Although the building of one battleship and two cruisers was cancelled with the implementation of the Revised Fifth Plan, it was decided to complete the work on the building of a total of approximately 780 craft, including eight converted aircraft carriers. Under the circumstances, it war most difficult to formulate the work allocation plan.

The spectacular military achievements during the initial stages

--20--

Chart No. 5

Shipbuilding Plan

Category

Individual
Tonnage
(standard displacement)

Number
of Vessels

Total Tonnage

Type
of
Vessel

Maximum
Speed and
Cruising Range

Main Armament

Remarks

Aircraft Carrier

17,460

2

34,920

Hiryu Type

34.0

12.7cm Twin Mount Guns

6

18 - 8,000

25mm Triple Mount Machine Guns

13

Aircrafts

57

"

17,260

2

34,520

"

32.0

18 - 8,000

"

17,500

9

107,500

Improved Hiryu Type

34.0

12.7cm Twin Mount Guns

6

18 - 8,000

25mm Triple Mount Machine Guns

13

Aircrafts

53

"

30,360

5

151,800

Taiho Type

33.3

10cm Twin Mount Guns

8

18 40,000

25mm Triple Mount Machine Guns

22

Aircrafts

54

Flying Boat Tender

4,650

3

13,950

Akisushima Type

37.5

12.7cm Twin Mount Guns

2

14 - 7,500

25mm Triple Mount Machine Guns

2

Aircraft

1

Cruiser Otsu

8,520

2

17,040

New Type

37.5

15cm Twin Mount Guns

4

18 - 6,000

8cm Triple Mount Guns

4

25mm Triple Mount Machine Guns

3

Quadruple Torpedo Tubes

2

Aircraft

2

Submarine Tender

12,479

3

37,437

"

21.0

12.7cm Twin Mount Guns

2

16 -10,000

25mm Triple Mount Machine Guns

4

Aircraft

1

Emergency Net Layer

1,608

1

1,608

Improved Wakataka Type

20.0

8cm Triple Mount Guns

2

14 - 3,000

13cm Twin Mount Guns

2

Destroyer Ko

2,077

8

16,616

Yugumo Type

35.0

12.7cm Twin Mount Guns

3

18 - 5,000

25mm Triple Mount Machine Guns

2

Quadruple Torpedo Tubes

2

Destroyer Otsu

2,701

23

62,123

Akizuki Type

33.0

10cm Twin Mount Guns

3

18 - 8,000

25mm Triple Mount Machine Guns

2

Quadruple Torpedo Tubes

2

Submarine Ko

2,390

3

7,170

I-13 Type

17.7

14cm Gun

1

Speed and Cruising Range show those on surface.

The same applies to other submarines.

16 - 22,000

25mm Triple Mount Machine Guns

4

Torpedo Tubes

6

Aircrafts

1

"

2,486

3

7,458

New Type

22.4

14cm Gun

1

16 -16,000

25mm Triple Mount Machine Guns

4

Torpedo Tubes

6

Aircraft

1

Submarine Otsu

2,140

14

29,960

I-54 Type

17.7

14cm Gun

1

16 - 21,000

25mm Triple Mount Machine Guns

2

Torpedo Tubes

6

Aircraft

1

"

2,330

18

41,940

New Type

22.4

14cm Gun

1

16 -14,000

25mm Machine Guns

2

Torpedo Tubes

8

Aircraft

1

Submarine Hei

2,095

15

31,425

I-52 Type

17.7

14cm Guns

2

16 - 21,000

25mm Machine Guns

2

Torpedo Tubes

6

"

2,285

25

57,125

New Type

22.4

14cm Guns

1

16 -14,000

25mm Machine Guns

2

Torpedo Tubes

8

Submarine Medium

965

43

41,495

Ro-35 Type

19.7

8cm Gun

1

16 - 5,000

25mm Machine Guns

2

Torpedo Tubes

4

--21--

[--22-- blank]

Shipbuilding Plan (Cont'd)

Category

Individual Tonnage (standard displacement)

Number of Vessels

Total Tonnage

Type of Vessel

Maximum Speed and Cruising Range

Main Armament

Remarks

Submarine Special

3,530

18

63,540

New Type

19.7

14cm Guns

2

14 - 30,000

25mm Machine Guns

6

Torpedo Tubes

8

Aircraft

3

Escort

940

34

31,960

Ukuru Type

19.7

12cm Twin Mount Gun

1

16 - 5,000

12cm Gun

1

25mm Twin Mount Machine Gun

2

Depth Charges

120

Mine Sweeper

646

36

23,256

No 19 Type

20.0

12cm Guns

3

14 - 2,000

25mm Twin Mount Machine Gun

1

Depth Charges

36

Submarine Chaser

440

30

13,200

No 13 Type

16.0

8cm Guns

3

14 - 2,000

13mm Twin Mount Machine Gun

1

Depth Charges

36

Oil

Tanker

18,300

7

128,100

Hayasui Type

16.5

12.7mm Twin Mount Machine Guns

2

9,000 tons of heavy oil and others for supply.

16 - 9,000

25 mm Triple Mount Machine Gun

2

Aircraft

6

"

15,600

124,800

New Type

20.0

12.7mm Twin Mount Machine Guns

2

6,800 tons of heavy oil and others for supply.

18 -10,000

25 mm Triple Mount Machine Gun

2

Aircraft

14

Storeship

910

7

6,370

Kinesaki Type

14.0

8cm Gun

1

Provisions

846 tons

12 - 3,500

13 mm Twin Mount Machine Gun

1

Fresh water

58 tons

Depth Charges

8

"

9,719

1

9,719

Irako Type

17.5

14 - 6,600

"

5,300

2

10,600

New Type

18.0

2cm Guns

2

Fresh provision.

450 tons

16 - 8,000

25 mm Twin Mount Machine Gun

2

Production material.

100 tons

Fresh water

500 tons

Target

Ship

2,540

5

12,800

"

33.0

13 mm Twin Mount Machine Gun

2

18 - 4,000

Depth Charges

18

Repair

Ship

9,600

2

19,200

Akashi Type

19.2

12.7cm Twin Mount Guns

2

14 - 8,000

25 mm Twin Mount Machine Gun

2

Survey

Ship

1,399

1

1,399

Tsukushi Type

19.7

14 - 8,000

Ice

breaker

7,040

1

7,040

New Type

17.0

12.7cm Twin Mount Guns

2

Icebreaking capacity: Approximately one meter thick.

14 - 5,500

25 mm Twin Mount Machine Gun

4

Aircraft

1

Light Mine Layer

720

12

8,640

Ajiro Type

20.0

12cm Guns

1

14 - 2,000

25 mm Twin Mount Machine Gun

1

Depth Charges

34

Motor

Torpedo Boat

75

18

1,350

Improved No 10 Type

30.0

25 mm Twin Mount Machine Gun

1

28 - 410

Torpedoes

4

Depth Charges

18

Total

361

1,156,061

--23--

[--24-- blank]

Chart No 6

Approved Extraordinary Military Appropriations for Fiscal Year 1943

Category

Individual
Tonnage

Number
of
Vessel

Unit
Price
per
Ton
(in Yen)

Unit
Price
per
Individual
Vessel
(In
1,000 yen)

Total
Sum
for
the
Category
(in
1,000 yen)

Remarks

Cruiser (Otsu)

3,520

2

5,678

4[],380

96,760

Flying Boat Tender

4,650

3

5,221

24,273

72,834

Emergency Net Layer

1,610

1

4,890

7,873

7,873

Aircraft Carrier (No 302 Type)

17,250

13

5,417

93,442

1,214,746

Aircraft Carrier (Improved No 130 Type)

30,400

5

4,294

130,550

652,750

Destroyer (Ko)

2,600

8

7,048

18,325

146,600

Destroyer (Otsu)

2,930

23

6,441

19,194

441,462

Submarine (Ko)

2,490

6

8,676

21,604

129,624

Submarine (Otsu)

2,282

32

9,187

20,965

670,880

Submarine (Hei)

2,240

40

9,428

21,119

844,760

Submarine (Medium)

1,000

43

8,686

2,686

373,498

Submarine (Special)

3,500

18

3,246

28,861

519,498

Submarine Tender

12,580

3

2,672

33,612

100,336

Escort

1,200

34

5,167

6,200

210,800

Submarine Chaser

420

30

6,948

2,918

87,540

Line Sweeper

700

36

5,621

3,935

141,660

Light Mine Layer

720

12

6,232

4,427

53,844

Oil Tanker (No 304 Type)

13,400

7

827

15,216

106,512

--25--

[--26-- blank]

Approved Extraordinary Military Appropriations for Fiscal Year 1943 (Cont'd)

Category

Individual Tonnage

Number of
Vessels

Unit
Price
per
Ton
(in Yen)

Unit
Price
per
Individual
Vessel
(in
1,000
yen)

Total
for
the
Category
(in
1,000
yen)

Remarks

Oil Tanker (New Type)

15,900

8

1,062

16,883

135,064

Icebreaker

6,800

1

2,432

16,538

16,538

Storeship (No 74 Type)

9,600

1

1,310

17,378

17,378

Storeship (New Type)

5,500

2

2,389

15,391

31,782

Storeship (No 261 Type)

1,000

4

2,923

2,928

11,712

Seven in the Plan

Survey Ship

1,600

1

4,710

7,536

7,536

Repair hip

9,420

2

2,444

23,027

46,054

Bomb Target Ship

3,000

5

3,355

10,064

50,320

Motor Torpedo Boat

100

18

23,850

2,385

42,930

Total

358

6,231,791

 

Note: The following was added in the fiscal year 1944 to equip oil tankers to carry aircraft.

No 304 Type

29,064,000 yen for seven ships; (¥ 4,152,000 per individual ship)

New Type

75,216.000 yen for eight ships; (¥ 9,402,000 per individual ship)

Total

104,280,000 yen

--27--

[--28-- blank]

Chart No 7

Status of naval vessels in the scheduled shipbuilding plan as at the end of June 1942.

Category

Not yet laid down

Already laid down

Already launched

Total

Remarks

Battleship

0

2

1

3

Third Plan:

MUSASHI

Fourth Plan

No 110 warship converted into aircraft carrier (SHINANO)

No 11 warship

suspended and dismantled.

Aircraft carrier

2

0

0

2

Flying boat tender

1

0

0

1

Cruiser

2

3

3

8

2 craft suspended (one each from Fourth & Urgent).
 Work on one craft temporarily suspended after launching (Urgent Plan: IBUKI)

Destroyer

25

8

6

39

Submarine

53

26

19

Escort

24

6

0

30

Minesweeper

24

6

1

31

Subchaser

15

9

4

28

Light minelayer

16

2

1

19

Auxiliary vessels

8

4

3

15

Light auxiliary vessels

96

39

1

136

Total

266

105

39

410

Of the total, three craft suspended or

cancelled.

Details are as shown in Charts 8 and 9

--29--

of the war added great impetus to the volume of work put out by all navy yards and private dockyards to which work was assigned.

However, with the increasing number of damaged ships entering the port, shortage of materials, and the gradual diminishing number of workers coupled with successive demands for newly planned smaller naval vessels arising from the new war situation, the substance of the Revised Fifth Plan changed daily. The results finally achieved are shown in Charts 8 and 9.

Air Strength

Combat Air Groups: The operational forces, together with the carrier and tender reserve forces at home and abroad, totalling 347 units (an increase of 219 units over the Fifth Plan and 83 units over the Fifth Wartime Plan) or 105 air groups (52 combat air groups assigned at home and 53 combat air groups assigned abroad) totalling 7,832 planes, combining the normal complement and immediate reserve, were to be maintained. (See Chart 10.)

Training Air Groups: 183 training air units (under 45 training air groups) were to be maintained. This was an increase of 27 units over the Fifth Plan. The normal complement of planes plus the immediate reserve was to be 4,939. (See Chart 10.)

Shipborne Air Strength: 129 units were to be maintained. The normal complement plus immediate reserve planes were to total 2,467. (See Chart 10.)

936 transport planes were to be maintained. (See Chart 10.)

--30--

Details - 2 -

Name of Plan

Category

Number
of
ships
planned

Number of Unfinished Ships

Remarks

Not
yet
laid
down

Already
laid
down

Already
launched

Total

"Urgent"

Cruiser

2

0

2

0

2

Ibuki and others

Aircraft Carrier

1

1

0

0

1

Unryu

Flying Boat Tender

1

1

0

0

1

Destroyer (Ko)

16

14

2

0

16

Hayanami and others

Destroyer (Otsu)

10

10

0

0

10

Shimozuki and others

Submarine (Otsu)

6

1

5

0

6

Submarine (Hei)

6

6

0

0

6

Submarine (Medium)

12

10

2

0

12

Submarine (Small)

9

7

2

0

9

Escort

30

24

6

0

30

Minesweeper

28

24

4

0

28

Subchaser

20

15

5

0

20

Light Minelayer

14

14

0

0

14

Auxiliary Subchaser

100

67

33

0

100

Auxiliary Minesweeper

16

11

5

0

16

Tanker

4

3

1

0

4

Kazahaya type

Motor Torpedo Boat

18

18

0

0

18

Total

293

226

67

0

293

"Supplement"

Submarine (Ko)

2

2

0

0

2

Submarine (Otsu)

12

9

3

0

12

Submarine (Medium)

15

15

0

0

15

Submarine (Refueling)

3

3

0

0

3

Target Ship

1

1

0

0

1

Total

33

30

3

0

33

--33--

[--34-- blank]

Chart No 9

Results of Ship Construction Under the Revised Fifth Plan

Category

Number of Ships

Planned

Completed

Under
construction

Not
yet
started
or
cancelled

Aircraft

18

2

3

13

Flying boat tender

3

0

0

3

Submarine tender

3

0

0

3

Cruiser

2

0

0

2

Emergency net layer

1

0

0

1

Destroyer

31

0

0

31

Submarine (Ko)

6

1

2

3

Submarine (Otsu)

32

0

0

32

Submarine (Hei)

40

0

0

40

Submarine (Medium)

43

0

0

43

Submarine (Special)

18

3

1

14

Escort

34

12

4

18

Minesweeper

36

0

0

36

Subchaser

30

3

0

27

Oil tanker

15

0

0

15

Storeship

10

0

0

10

Target ship

5

1

1

3

Repair ship

2

0

0

2

Survey ship

1

0

0

1

Ice breaker

1

0

0

1

Light minelayer

12

0

0

12

Motor Torpedo boat

18

0

0

18

Total

361

22

11

328

--35--

Flight personnel were estimated at 40,500. The number of teams of flight personnel for large planes was to be twice the number for the wartime plane complement and for other types of planes the number was to be one and a half times the normal complement. The required number of personnel for training groups was to be maintained constantly.

Flight engineers were estimated at 2,470 and the assigned personnel ratio was to be the same as for flight personnel. Aircraft engineers were to total 57, 800 and ordnance engineers 19,400.

In order to execute this plan, it was necessary to emphasize aircraft production as a national policy and to take measures to give top priority to the Navy with regard to the allotment of mate-rials.

It was evident from the Navy Minister's reply to the Chief of the Naval General Staff that it was considered that there were many problems to overcome. Principal among these was the fact that if the rate of consumption of materials in the future was to be assumed to be the same as that during the four months from the outbreak of war to the end of March 1942, a delay of a year could be anticipated in the completion of planes. The anticipated date of completion would then be the end of the fiscal year 1947. Also, if the complement of flight personnel were increased by the approximate rate of 1.2 times the plane complement, their training would be generally completed in parallel with the rate of manufacture of the planes.

--36--

Chart No 10

The Air Strength Increase Plan for Fiscal Year 1942 (The Revised Fifth Plan)

The combat air group

Air Strength

Category

Number
of
Planes

per
Air Unit

Required
Number
of

Air
Unit
in
Revised
Fifth Plan

Required
Number
of
Air
Units
in
Fifth
Plan
(Wartime
Strength)

Increase
or
decrease
of
Air
Units
In
Revised
Fifth
Plan

Land-based

air strength

Land fighter Plane

18/6

100

44

(+) 56

Fighter-bomber

60

26

(+) 34

Land reconnaissance Plane

9

4

(+) 5

Land attack

Large

10

20

(-) 10

Plane

Medium

60

30

(+) 30

Seaplane fighter

12

22

(-) 10

Seaplane bomber

12/4

18

18

0

Patrol Plane

26

16

(+) 10

Transport Plane

18/6

4

4

0

Flying Boat

Large

9/3

0

24

(-) 21

Medium

12

24

(-) 12

Air strength prepared

for converted

vessels

Carrier fighter

18/6

13

7

(+) 6

Carrier bomber

20

11

(+) 9

Carrier attack Plane

Carrier reconnaissance Plane

3

0

(+) 3

Seaplane fighter

0

2

(-) 2

Reconnaissance Seaplane

12/4

0

12

(-) 12

Total

347

264

(+) 33

Note: The strength of Large land attack planes in wartime is the same as that in peacetime.

The combat air group figures shown are wartime; the strength in peacetime was one half the wartime strength.

--37--

[--38-- blank]

Chart No 10 (cont'd)

Shipborne air strength

Carrier planes: 106 units (Number of aircraft of one unit: 18 normal complement and 6 immediate reserves)

Seaplanes: 23 units (Number of aircraft of one unit: seaplane fighters, 18 end 6; reconnaissance seaplanes, 12 and 4) Transport planes

To be assigned in accordance with the following:

Units to which planes will be assigned

Standard of assignment

Remarks

Land attack plane unit

Three large planes for one air unit

Flying boat unit

Two large planes for one air unit

Land base small plane unit

One large plane and one small plane for one air unit

Carrier plane unit

One-half of the number prescribed by the standard of assignment at the time of actual loading shall be maintained.

Shipborne seaplane unit

Training unit

One large plane and one small plane for one air group

Navy Ministry and Navy Guard Districts

One large plane and one small plane for each naval district and guard district; two large planes and two small planes for the central office.

Total..........926 planes

--39--

Chart No 10 (Cont'd)

The training air group

Category

Number of planes per unit

Required number of Air Units in revised Fifth Plan

Required number of Air Units in Fifth Plan

Training aircraft

12/12

93.0

183.0

73.0

156.0

Combat aircraft

Same as number of aircraft of combat air unit, but the number of combat aircraft of the pilot-observer training unit shall be the same as that of its reserve aircraft.

90.0

83.0

--40--

If the complement were increased by 1.5 times, the completion of the training would be delayed another year, or until the end of the fiscal year 1948.

Although the naval authorities started the plan with high hopes of its successful completion, many difficulties confronted them, both because of the unprecedentedly large size of the plan and also because the operational situation had begun to deteriorate. The production increase of aircraft failed to show the expected progress and losses increased tremendously. During the fall of 1942, in the Southeast Area, the annual loss of planes rose to 95 percent. Thus, the plan which was intended to be the main prop of strength maintenance until the termination of the war, had to be adjusted gradually with various emergency supplementary plans as operations developed, in order to meet new situations as they arose.

Supplementary Adjustments to Revised Fifth Plan

The whole substance of the Revised Fifth Plan, through successive heated deliberations since the outbreak of the war and through a drastic revision as the result of the Battle of Midway, was finally decided in early August, 1942 and put into motion. The Chief of the Naval Affairs Bureau of the Navy Ministry submitted the following notification to the authorities concerned on 30 September, 1942 in order to notify them that the name of the revised plan had been abbreviated to "Revised Fifth Plan" and to obtain a

--41--

unanimous understanding as to the relation between the Revised Fifth Plan and the War Preparation Acceleration and Execution Plan.

Naval Affairs Bureau First Secret Document No. 738

30 September 1942

From: Chief of Naval Affairs Bureau, Navy Ministry

To: Chiefs of Bureaus concerned, Navy Ministry

Chief, Naval Technical Department

Chief, Naval Aeronautical Department

Chief, Naval Civil Engineering Department

Chief, First Bureau, Naval General Staff

Chief, Second Bureau, Naval General Staff

Notification Concerning the Abbreviation of the Name of the New Armament Plan.

It shall be understood that those plans of the requested naval strength mentioned in the Naval General Staff Document No. 191 (Wartime Plan for the Fiscal Year 1942), with the exception of the plan for the fiscal year 1939 (Fourth) and the Wartime Plan for the Fiscal Year 1941" (Urgent) will be known by the abbreviated title of "Revised Fifth Plan".

It shall be known that in reference to the relation between the abovementioned plan and the War Preparation Acceleration and Execution Plan, the latter's strength will correspond to that which is represented by the formula "Fifth + A - B".

Supplementary Ship Construction Plan to Revised Fifth Plan

Soon after the Revised Fifth Plan was begun the war developed into a large scale war of attrition, struggling for the control of the Southeast Area. Therefore, the Naval General Staff demanded the construction of an additional 18 submarines (Type TEI) in October 1942, and 42 destroyers (Type TEI) in early 1943.

The following Naval General Staff Secret Documents No. 309 and No. 37 refer to this construction.

--42--

Naval General Staff Secret Document No. 309

21 October 1942

From: Chief of Naval General Staff

To: Navy Minister

Request concerning Additional Ship Construction to the Wartime Air Strength Expansion and Ship Construction and Replenishment Plan for Fiscal Year 1942.

In view of the development of the situation in the Greater East Asia War, I hope the abovementioned request will be accepted and initiated in accordance with the program mentioned in the annexed document.

(Annex Document)

Supplementary Wartime Ship Construction and Replenishment Plan for Fiscal Year 1942

The plan shall be commenced in fiscal year 1942 and completed by the end of 1944.

The ships to be constructed and their main essentials are shown on Chart No. 11.

Naval General Staff Secret Document No. 37

2 February 1943

From: Chief of Naval General Staff

To: Navy Minister

Request Concerning Additional Ship Construction for the Wartime Air Strength Acceleration and Ship Construction Replenishment Plan for Fiscal Year 1942.

In view of the development of the war situation since the start of the Greater East Asia War and taking into consideration its future development, we believe that it is of vital importance to increase the number of destroyers. Therefore, we hope that you will accept the request and initiate the execution of the project in accordance with the plan in the annexed document.

Annexed Document

The Second Supplementary Plan for Wartime Ship Construction and Replenishment Plan for Fiscal Year 1942

--43--

The plan shall be started in the fiscal year 1943 and completed by the end of the fiscal year 1945.

The ships to be constructed and their main essentials are shown on Chart No. 12.

The Navy Ministry fully acknowledged the operational demands of this plan but felt that if it were put into force at this time great confusion would result. The Revised Fifth Plan, had just been started and the Execution Plans for Expediting War Production (First Period) were under way. It was decided, therefore, that the execution of the proposed plan should be studied first and then woven into the Execution Plans for Expediting War Production (Second Period) which were to be determined in the near future. Moreover, budgets and items were to be disposed as supplements to the Revised Fifth Plan.

The approved budget and details of the actual results achieved are shown on Chart No. 13.

--44--

Chart No 11

Ships to be Completed End of Fiscal Year 144

Category

Number of Ships

Standard Displacement

Speed

Cruising Range

Other Essentials

Subseries (TEI)

11

approx 1,500 tons

Surface over 12 knots

Submerged speed approx 6 knots

Surface cruising range approx 15,000 s. miles at 10 knots. Submerged cruising range approx 60 m. miles at 3 knots.

1. 40 caliber 14cm gun

1

2. Two 25mm single mount machine guns. Portable type which can be mounted at the leading deck of the special type cargo lighters.

3. Two 53cm bow torpedo tubes

Two torpedoes

4. Main Personnel and Arms Loaded

a. Land combat personnel

approx 110

b. Land combat equipment

approx 10 tons

c. Special landing barges

2

d. Special rubber boats

several

5. Others

a. Submersible limit

75 meters

b. Continuous cruising endurance

approx 2 months

e. Special consideration shall be given for equipping so that loading and unloading will be done promptly and easily.

--45--

Chart No 12

Ships to be Completed End of Fiscal Year 1945

Category

Number
of

Ships

Standard
Displacement

Speed

Cruising
Range

Other Essentials

Destroyer (TEI)

42

1,250 tons

Approx 28 knots

Approx 3,500 n. miles at 18 knots

1. One 12.7cm twin mount dual purpose gun

One 12.7cm twin mount dual purpose gun

2. Four 25mm triple mount machine guns

3. One 53cm six mount torpedo tubes

Six torpedoes

4. Thirty-six depth charges

Two depth charge throwers

5. One echo ranging set

One hydrophone

6. One radar

7. Two 10 M Special cargo lighters

Two cutters

--46--

Chart No 13

Approved Budget and Actual Results Achieved 1944

Category

Tonnage

Number
of
Ships

Cost
per
Ton

in
yen

Cost
per
Ship
in
Thousand
Yen

Total
in Thousand Yen

Remarks

Destroyer (TEI)

1,260

32

7,041

9,326

29,432

Approved in the fiscal year 1944

"

"

10

7,430

9,614

96,140

Approved in the fiscal year 1945

Submarine (TEI)

1,500

11

6,289

9,426

103,686

Approved in the fiscal year 1944

Total

53

498,258

Total in Revised Fifth Plan

411

6,730,049

Actual Results

Category

Number of Ships

Planned

Completed

Under
construction

Not
yet
started
or
cancelled

Destroyer (TEI)

42

26

5

11

Submarine (TEI)

11

11

0

0

Total

53

37

5

11

Total in Revised Fifth Plan

414

59

16

339

--47--

Chart No 13 (cont'd)

Category

Individual
Tonnage
(Standard
Displacement)

Number
of
Ships

Total
Tonnage

Type

Top
Speed
and
Cruising
Range

Main Armament

Destroyer (TEI)

1,262

42

53,004

New Type

27.8 knots

3,500 n. miles at 16 knots

One 12.7cm twin mount gun

One 12.7cm single mount gun

Four 25mm triple mount machine gun

One 03 Type torpedo tube.

Submarine (TEI)

1,470

11

16,170

"

13.0 knots

15,000 n. miles at 10 knots

One 14cm gun

Two 25mm machine guns

Two torpedo tubes

Total

53

69,174

Total in Revised

Fifth Plan

414

1,225,235

--48--

Appendix I

Naval General Staff Secret No 191

30 June 1942

To: Minister of the Navy

From: Chief of the Naval General Staff

Request Concerning Increase of Wartime Air Strength and Building and Replenishment of Navy Vessels for Fiscal Year 1942.

In reference to the building and replenishment of Navy vessels and an increase in air strength, requests were previously forwarded for the plan for the fiscal year 1942, and later, with the opening of hostilities for the wartime plan for the fiscal year 1941. In view of subsequent developments and the enforcement of an enormous armament expansion program by the U.S. Navy, it has become urgently necessary to replenish and maintain wartime armament by revising a portion of the previously determined plans. Accordingly, I request you to take the necessary steps to execute this measure as set forth in the attached plan.

Attached Plan

Wartime Air Strength Expansion and Ship Replenishment Plan for Fiscal Year 1942.

In view of the battle lessons gained since the outbreak of war,

the development of the war situation and the enforcement by the U.S.

Navy of a gigantic armament expansion plan, strength most suitable

for bringing the war to a successful conclusion shall be selected

and be held in readiness.

--49--

In consideration of materials available and productive capacity, at this juncture, strength absolutely indispensable shall be held in readiness, according to the following order of urgency:

Aircraft

Aircraft carriers

Submarine and anti-submarine forces

Other naval vessels

With regard to the expansion of air strength, the contents of the Fifth Plan shall be revised in accordance with the following policy and the completion of the pre-arranged plans shall be expedited to the utmost.

Aircraft

In view of our progress in experiments in the light of current battle lessons and our production capacity, in order to meet the changing situation, production emphasis shall be placed on aircraft of such types as are most needed for promoting the war. Air Bases

Emphasis shall be placed on front-line bases according to the changes in the situation. The maintenance of air bases in the homeland area shall, for the time being, be limited to minimum requirements.

Expansion of Air Strength

The First Phase Air Strength Plan, included in Ship Replenish-

--50--

Chart. No 1

Land-based Air Strength

Strength

Kind of aircraft

Normal
plane
complement
for
one
air unit

Number
of
units required

Number
of
units
called
for
Fifth Plan

Increase
or
decrease
in
number
of
units
after
revision

Land based air strength

Land fighter plane

Interceptor

18

40

44

(+) 56

Long range fighter

60

Fighter-bomber

60

26

(+) 3A

Land reconnaissance plane

9

4

(+) 5

Land attack

Large

10

20

(-) 10

Medium

60

30

(-) 30

Seaplane fighter

12

22

(-) 10

Seaplane bomber

12

18

18

0

Patrol plane

26

16

(+) 10

Transport plane

18

4

4

0

Flying boat

Large

9

0

24

(-) 24

Medium

12

24

(-) 12

Air strength replacement for carrier borne planes

Carrier fighter

15

13

0

(+) 13

Carrier attack plans

20

0

(+) 20

Carrier bomber

Carrier reconnaissance plans

3

0

(+) 3

Total

347

232

(+) 115

--51--

ment and Air Strength Expansion Plan for Fiscal Year 1942 contained in Naval General Staff Secret Document No. 471, shall be revised as follows:

Land-based air strength

The land-based air strength shown on Chart I indicates wartime strength. The immediate reserve of planes shall be one-third of the normal plane complement.

Although the number of large land attack plane units is 10 for the time being, speedy construction of a further 10 units during and after the fiscal year 1947 shall be considered.

Although peacetime strength is considered to be generally one-half of the wartime strength, conferences shall be held in accordance with the situation at the time of the conversion.

Shipborne air strength

Kind of aircraft

Normal
plane
complement
for
one
air
unit

Number
of
units
necessary
for
standing
vessels

Number
of
units
necessary
for
converted
ships

Total
number
of
air
units

Carrier fighter

18

33

5

38

Carrier bomber

51

9

60

Carrier attack plane

Carrier reconnaissance plane

8

0

8

Seaplane fighter

2

0

2

Reconnaissance seaplane

12

13

8

21

Total

107

22

129

--52--

Land-based Air Strength

Strength

Kind of aircraft

Normal
plane
complement
for
one
air
unit

Number
of
units required

Number
of
units
called
for
Fifth Plan

Increase
or
decrease
in
number
of
units
after
revision

Land based air strength

Land fighter plane

Interceptor

18

40

44

(+) 56

Long range fighter

60

Fighter-bomber

60

26

(+) 34

Land reconnaissance plane

9

4

(+) 5

Land attack plane

Large

10

20

(-) 10

Medium

60

30

(+) 30

Seaplane fighter

12

22

(-) 10

Seaplane bomber

12

18

18

0

Patrol plane

26

16

(+) 10

Transport plane

18

4

4

0

Flying boat

Large

9

0

24

(-) 24

Medium

12

24

(-) 12

Air strength replacement for carrier borne planes

Carrier fighter

15

13

0

(+) 13

Carrier attack plane

20

0

(+) 20

Carrier bomber

Carrier reconnaissance plane

3

0

(+) 3

Total

347

232

(+) 115

The immediate reserve of planes shall generally be limited to approximately one-third of the normal plane complement, part of which shall be placed on board ships and the remainder held in readiness at the replacement bases for carrier-borne planes and inner combat bases.

Training air units

Kind of aircraft

Normal plane complement for one air unit

Number of units required

Total No. of air units

Training plane

12

93.0

183.0

Combat aircraft

Same as combat air unit

90.0

The immediate reserve of training planes shall consist of the normal plane complement.

The number of combat aircraft for pilot and reconnaissance training units shall be the same as the normal plane complement and for other training air units it shall be one-third of the normal plane complement, with the exception of flying boats, which shall be same as the normal complement.

Training planes

Transport planes shall be held in readiness in accordance with the following:

--53--

Units

Standard of assignment

Remarks

Land attack plane

3 large planes for one air unit

Equivalent to one-half of shipborne shall be held in readiness.

Flying boat

3 large planes for one air unit

Land based small aircraft

2 large planes for one air unit

Carrier plane

Shipborne seaplane

Training air group

1 large and 1 small planes for one air group

Navy District, Guard District and Navy Ministry

1 large plane and I small plane for Naval District, Guard District and Fleet Headquarters. 2 large planes and 2 small planes for the central authorities.

Flight personnel

In regard to the personnel of units committed in an operation, the number of teams shall be twice that required for large planes of wartime normal plane complement and one and a half times for other types of planes. The training shall train personnel so as to meet these requirements.

Ten thousand (10,000) pilots and observers shall be trained each year during the war after the fiscal year 1945, and, 10 percent of this number shall be earmarked as reserve personnel.

Up to 2,800 officers, shall be trained immediately and assigned

--54--

to posts of the Division Officer or lower posts.

Air Group and Air Base

Operational air bases and carrier-borne plane replenishment bases shall be organized by the end of the 1946 fiscal year in accordance with Chart 2 and the air groups and base units shall be organized according to the demand of the operations. The air group disposition program during the completion of this revised plan shall be as shown on Chart 3. However, it may be changed according to future operations and other conditions.

Construction and Replenishment of Ships

Ships Stipulated in the Construction Plan for Fiscal Year 1939

No. 110 Warship;

The warship shall be converted into an aircraft carrier by the end of 1944. Essential particulars shall be discussed later.

No. 111 Warship;

Construction shall be discontinued and the ship shall be immediately dismantled.

No. 137 Warship;

Construction shall be discontinued.

Ships Stipulated in the Wartime Construction Plan for Fiscal Year 1941

No. 300 Warship;

This ship shall be launched quickly but further work shall then be suspended.

--55--

No. 301 Warship:

The construction shall be discontinued.

The first period plan shown in the Naval General Staff Secret Document No. 471 shall be revised as shown in Chart 4 and completed by the end of 1947.

In regard to increasing the number of converted aircraft carriers, discussion shall be held later.

Ships to be constructed, both essential particulars of new and improved Fifth Plan type are as shown in Chart 5.

--56--

Appendix II

Official Reply from the Ministry of Navy:

Secretariat Secret Document No 9599-2

3 August 1942

From: Minister of Navy

To: Chief of Naval General Staff

Reply to the Request Concerning the Wartime Reinforcement of Air Strength and Additional Construction of Vessels for Fiscal Year 1942.

Although it is anticipated that, in view of the current situation, many difficulties will be encountered in executing the above-mentioned matters requested in the Naval General Staff Secret Document No 191, every effort will be exerted to meet your wishes. As for the details of the plan, the Vice-Minister of Navy, will communicate with the Vice-Chief of Naval General Staff in regard to details of the plan,

(The End)

Reference Material Added to the Reply

30 July 1942

From: Bureau of Naval Affairs, Navy Ministry

Prospect of maintaining the Strength Requested in Naval General Staff Secret Document No 191.

Air Strength: The date scheduled for the completion of air—

--57--

craft should be decided in accordance with production capacity and the rate of loss. Therefore, if we estimate the future rate of loss from the outbreak of war to the end of last March as a provisional basis, it is expected that the plan will be completed at the end of fiscal year 1947. The training of personnel will be approximately 20 percent more than the complement believed necessary generally for the completion of the plan. In case 50 percent more personnel than the complement is required, the completion of training will be delayed a further year.

As the maintenance of patrol planes and fighter-bombers cannot possibly meet the demand of the Naval General Staff, it is deemed necessary to substitute other types of planes for them and that further study and investigation be conducted as to the capabilities of maintaining air bases and disposing of strength.

Naval Vessels: The current situation is such that the completion of the construction of Navy vessels must inevitably be delayed approximately one year chiefly because of the shortage of materials and labor. Furthermore, there are many production installations of various types which, in executing this plan, require expansion or new construction. Although concrete measures are being studied, it is impossible, for the time being, to make ample preparations for expanding the dry docks, mooring docks and supply facilities required for the increase in strength of naval vessels. Furthermore, an increase in the number of damaged ships to be repaired will exert considerable influence upon the execution

--58--

of the plan.

Construction of Merchant Ships: Shipping space is an absolutely necessary factor in the prosecution of a war. In view of the fact that the construction of merchant vessels since the outbreak of the war has failed to make as good progress as anticipated, various emergency measures are now being studied. One is to put the construction of merchant vessels under the single control and jurisdiction of the Navy by regarding it as part of the naval armament; another is aimed at the smooth supply of materials and labor. It is impossible to maintain naval vessels by restricting the construction of merchant ships as was done before the war. It is the duty of the Navy to take the responsibility for the maintenance and strengthening of shipping.

Arms: In view of the present situation under which the supply of various kinds of arms is very difficult, increased production required by the projected expansion of naval strength cannot be achieved unless every possible means is taken and utmost effort are exerted. It is especially true in the case of air arms The productive capacity for fuel is expected to be increased to approximately 70 percent of present requirements.

Facilities: In view of the recent shortage of labor and materials, it is evident that the nation's production capacity is reaching its maximum. Consequently, in order to meet production requirements, it is imperative to further study the priority system.

--59--

Materials: For the execution of this program, a shortage of 300,000 to 400,000 tons in the annual quota of steel as well as a considerable shortage in aluminum is expected. The situation in regard to other special metals is also expected to worsen. Therefore, the Navy must plan an allotment increase in the material mobilization quota and the nation must expedite the development of resources for these materials and increase their production.

Transportation: As a result of the proposed expansion of armament and extension of operational lines, increase in transportation capacity would inevitably be required. However, present conditions make it impossible to meet these requirements. Unless these difficulties can be surmounted, the expansion of armament and preparations for war will be hindered to a considerable degree.

Military men: According to the program, the fixed number of commissioned personnel at the end of fiscal year 1947 is estimated at approximately 760,000 and that of the wartime personnel at approximately one million. The annual minimum number of the required conscripts is estimated at 150,000. However, according to the number of personnel to be allotted to the Navy, determined by the recent agreement between the Army and Navy, there will be an annual shortage of approximately 40,000. Consequently, it calls for further consideration by Army and Navy authorities.

Laborers: It is estimated that the total number of laborers required during the fiscal year 1947 will be more than 2,600,000 (at present it is estimated to be 1,600,000), inclusive of laborers

--60--

required by plants outside the Navy's direct control. Moreover, when the estimated average loss of laborers which at 10 percent, is taken into consideration, a further 300,000 to 350,000 laborers will be repaired each year. However, the annual allotment of conscript laborers expected by the Navy ranges at the most between 200,000 to 250,000. Such being the case, the shortage of laborers must be compensated for by the utmost utilization of Koreans, Formosans, prisoners of war and inhabitants on the spot, as well as by the reduction of personnel in charge of administrative affairs and by improving efficiency.

Expenses: Roughly estimated expenses necessary for the execution of the established armament and war preparation plans, as well as the existing plans, are as follows: (in 100 million yen)

Fiscal Year

1943

1944

1945

1946

1947

Organizational expenses

102

95

91

88

74

Maintenance expenses

26

38

49

59

70

Total

128

133

140

147

144

As the Army expenses required approximately the same amount, it became necessary to float loans to raise the money.

Conclusion: In view of the urgency of the situation, important items in this plan will be initiated. However, in view of the fact that there are many difficulties to be surmounted in order to accomplish Naval General Staff's Plan, utmost efforts will have to be made to realize it by adopting the priority system and by adjusting the relations between various departments to the fullest extent.

--61--

At the same time, in order to accomplish the proposed expansion of air strength (inclusive of aircraft carriers, communications and arms for aircraft, as well as many other items related to aircraft), it is necessary to prepare a plan to abandon, or postpone, the maintenance of other strength. Furthermore, it will be necessary to take various measures to give priority to the Navy with reference to the allocation of personnel and materials.

--62--

Japanese Monograph No. 172

OUTLINE OF NAVAL ARMAMENT AND PREPARATIONS FOR WAR

Part V

PREPARED BY

MILITARY HISTORY SECTION

HEADQUARTERS, ARMY FORCES FAR EAST

DISTRIBUTED BY

OFFICE OF THE CHIEF OF MILITARY HISTORY

DEPARTMENT OF THE ARMY

This is the fifth of a series of six monographs in regard to Japan's naval armament in preparation for and during the Pacific War.

Additional monographs covering Japan's naval armament plans are:

Mono No

Outline of Naval Armament and Preparations for War, Part I

145

Outline of Naval Armament and Preparations for War, Part II

149

Outline of Naval Armament and Preparations for War, Part III

160

Outline of Naval Armament and Preparations for War, Part IV

169

Outline of Naval Armament and Preparations for War, Part VI

174

18 September 1952

--iii--

Preface

Through Instructions No. 126 to the Japanese Government, 12 October 1945, subjects: Institution for War Records Investigation, steps were initiated to exploit military historical records and official reports of the Japanese War Ministry and Japanese General Staff. Upon dissolution of the War Ministry and the Japanese General Staff, and the transfer of their former functions to the Demobilization Bureau, research and compilation continued and developed into a series of historical monographs.

The paucity of original orders, plans and unit journals, which are normally essential in the preparations of this type of record, most of which were lost or destroyed during field operations or bombing raids rendered the task of compilation most difficult; particularly distressing has been the complete lack of official strength reports, normal in AG or G3 records. However, while many of the important orders, plans and estimates have been reconstructed from memory and therefore are not textually identical with the originals, they are believed to be generally accurate and reliable.

Under the supervision of the Demobilization Bureau, the basic material contained in this monograph was compiled and written in Japanese by former officers, on duty in command and staff units within major units during the period of operations. Translation was effected through the facilities of Allied Translators and Interpreters Service, G2, General Headquarters, Far East Command.

This Japanese Operational Monograph was rewritten in English by the Japanese Research Division, Military History Section, Headquarters, Far East Command and is based on the translation of the Japanese original. Editorial corrections were limited to those necessary for coherence and accuracy.

--v--

TABLE OF CONTENTS

Page

Second Stage War Production Plan (Second Revision of Fifth Plan) March 1943 - April 1945

1

Second Period War Production Acceleration Plan

2

Third Phase War Preparations Plan

3

Recommendations by Navy General Staff

4

The Naval War Preparations Research Committee Conference

5

Naval Aeronautical Department

5

Stores Bureau

11

Navy Technical Department

13

Navy Civil Engineering Department

14

Organization, Equipment and Capacity of Construction Units

14

Maintenance Plans for Construction Units

16

Personnel Bureau

17

Education Bureau

20

Military Preparation Bureau

22

Labor

25

Tentative Compromise Plan Proposed by the Navy Affairs Bureau ("HI" Study)

29

Negotiations with the Army in Regard to Allocation of Materials and Production Facilities for Aircraft Production

32

Interim Decisions

33

--vii--

Page

Problems Related to Administrative Inspection and Monitions Ministry

35

Execution Plan and Outline of its Progress

37

Shipbuilding Program

37

Aircraft Production

45

CHARTS

No.

1.

Naval Vessels Added to 1943 - 1944 Shipbuilding Plan

39

2.

Shipbuilding Program 1945

41

3.

Construction of Naval Vessels 1943 - 1944

43

4.

Actual Aircraft Production (Monthly and Quarterly) for 1943 and 1944, Also Figures for 1941, 1942 and 1945

49

APPENDICES

I.

Navy Ministry's Inquiry on the Formulation of the Second Period Execution Plan for the Acceleration of War Preparations, 15 March 1943

53

II.

Navy General Staff Top Secret Document No 142, 22 April 1943

57

III.

Navy Ministry's Reply Concerning the Wartime Construction and Replacement of Naval Vessels and the Strengthening of the Ground Defenses in the 1943 Fiscal Year

65

IV.

Material for the Ninth Meeting of the Naval War Preparations Research Committee of Imperial General Headquarters

73

--viii--

Second Stage War Production Plan (Second Revision of Fifth Plan) March 1943-April 1945

As the Revised Fifth Plan and the First Period War Production Acceleration Program were put into effect, each department was called upon to exert the utmost effort to complete its part in the program.

The Guadalcanal Campaign, begun on 7 August 1942, completely upset all calculations for these plans, as it became necessary for the Japanese Navy to commit cruisers, destroyers and submarines to this campaign which it had been previously planned to hold in readiness for the all-out decisive battle. Although the Japanese Navy inflicted considerable losses on the enemy during this period, the damage to Japanese ships and aircraft was far greater than anticipated.

In order to cope with this situation, the Naval General Staff requested the additional construction of 11 submarines and 42 destroyers. (See Monograph No 169, p. 14) The Navy Ministry and fleet authorities felt, however, that there was not sufficient time to undertake this work and that it was far preferable to construct high speed Navy transports of a new type, designed so that they could be mass produced. These ships could then be used exclusively for transporting troops and supplies. Another factor affecting the policy of the Navy Ministry was the sudden increase in shipping losses caused by enemy submarines after October 1942. (Monthly shipping losses up to September 1942 averaged 50,000 tons, but increased to 200,000 tons

--1--

after October 1942.) The Japanese Navy admitted that they had underestimated the efficiency of the United States submarines and recognised the need for speedily constructing Navy transports, antisubmarine vessels and small craft for local operations. This made a complete change necessary in war preparations. From the beginning of 1943, therefore, both the Navy Ministry and the Navy General Staff investigated the situation. As a result, the Second Period War Production Acceleration Plan was drawn up.

Second Period War Production Acceleration Plan

In order to minimize the confusion resulting from the constant change in war production plans and to speed up the work without waiting for agreement to be reached between the Navy Ministry and the Navy General Staff with respect to the change in naval strength in the Revised Plan, on 15 March 1943 the Naval Affairs Bureau requested information from the departments concerned in regard to formulating the Second Period Execution Program for the Acceleration of War Production. (See Appendix I.) After consultation with the section chiefs concerned, the details of this proposal were approved by the Emergency War Production Acceleration Committee on the same day.

In order to effect the drastic revision of policy necessary to meet the change in the operational situation, the Navy General Staff, after investigation of the situation, requested the Navy Ministry

--2--

for details of the Wartime Ship Construction Replenishment Program and the Land Defense Reinforcement Program described in the appended plan to Naval General Staff Secret Document No 142, dated 22 April 1943. (See Appendix II.)

The Navy Ministry stated that it was absolutely impossible to meet the demands of the Navy General Staff. It was felt that the Navy General Staff made new and unreasonable demands each time the war situation changed. It was not until June 1943, after investigating the suspension of old armament and war preparation plans and in coordination with the Revised Fifth Replenishment Plan, that the Navy Ministry was able to decide on the Second Phase War Preparations Plan. A formal reply outlining the execution of the plan was submitted to the Navy General Staff by the Navy Ministry on 3 June 1943. (See Appendix III.)

Since the Second Phase War Preparations Plan included only ships, and excluded air defense strength, the progress of the air defense program will be mentioned in conjunction with ship strength in the Third Phase War Preparations Plan.

Third Phase War Preparation Plan

Immediately after the commencement of the Second Phase War Preparations Plan, the war entered the Third Phase Operations. This may be considered as beginning with the withdrawal from Guadalcanal about 7 February 1943, although the Imperial General Headquarters

--3--

Navy Directive on this phase was not issued until 25 March 1943, and the Combined Fleet did not announce it officially until 15 August 1943. About this time, the Japanese Armed Forces lost the initiative in operations and were compelled to resort to defensive or passive warfare.

In April, the Commander in Chief of the Combined Fleet was killed in action. In May, the Japanese forces on Attu were wiped out. In the Solomons and New Guinea, the Japanese forces gradually retreated to the northwest under heavy pressure from the Allied forces.

Both Army and Navy headquarters as well as the Japanese Government were urged to take drastic measures to cope with the situation. Students were mobilized and all material previously discarded as outmoded was collected to assist in the production of necessary war machinery.

The third revision of the Fifth Replenishment Plan (Revised Fifth Plan) was the same as the Third Phase War Preparations Plan.

Recommendations by Navy General Staff.

On 11 August 1943, the Navy General Staff submitted a proposal for the Third Phase War Preparations Plan. (See Appendix IV.) They stated the number of planes, ships and personnel required, but gave no specific information as to how these were to be obtained, or the date on which work would be completed. The proposal was written in

--4--

the form of pamphlets which were distributed at the preliminary meeting with the Ministry. No formal documents were submitted, as had been the case in the past. The Navy General Staff requested that, upon completion of the study of these pamphlets by the Navy Ministry, a meeting be held of the Naval War Preparations Research Committee, at which the responsibilities of each department of the Ministry would be explained.

The Naval War Preparations Research Committee Conference

The Navy Ministry was somewhat reluctant to accept this proposal from the Navy General Staff, but, at the same time, was prepared to discuss bottlenecks which impaired the efficiency of the departments in preparing war materials. It was decided, therefore, that, as soon as the necessary study had been made of the proposal, it would be referred to the War Preparations Research Committee in order to obtain a compromise.

A conference was held with this Committee about 20 September 1943. A summary of the report prepared by the War Preparations Execution Department was as follows:

Naval Aeronautical Department

The present plan to produce 15,000 planes during the fiscal year 1944 was considered the absolute limit of the capacity of the aircraft industry. The Navy General Staff plan, however, aimed at

--5--

a drastic twofold increase in production. Under existing conditions the realization of this plan was quite impossible. However, it was recognized that the replenishment of naval air strength might prove an essential factor in finally deciding the destiny of Japan, and the cooperation of the entire Navy was required to overcome all difficulties. Further, it was necessary to obtain the cooperation of the Army so that various departments might work together to obtain the objective. It was, therefore, decided that:

During the fiscal year 1943, the number of planes to be manufactured would be increased to 9,800, upon the early completion of the previously established plan for the production of 8,200 planes. This was 86 percent of the planes requested by the Navy General Staff for the fiscal year 1943, but 1600 planes short of their stated requirements.

During the fiscal year 1944, 4,300 planes of the 30,200 planes requested by the Navy General Staff would be produced by diverting a part of the production capacity of the Array, while the remaining planes would be manufactured by relying on the full cooperation of the Navy Technical Department.

Flight Personnel: It was estimated that the number of flight personnel required to be maintained, in order to meet the request of the Navy General Staff, would be 17,000 at the end of the fiscal year 1943 and 42,000 at the end of 1944. The number to be trained in accordance with the present program during the fiscal year 1943

--6--

was 8,460 and during the fiscal year 1944 was 18,560, while an increase of that number by 917 in 1943 and 10,118 in 1944 would be possible under the new program. Should both these programs be fulfilled, and the personnel be trained, it would mean that 88.6 percent of the Navy General Staff's request would be met in 1943 and 84.1 percent in 1944. In order to accomplish this during the 1943 fiscal year it would be necessary to advance the graduation date to the end of March 1944 instead of the end of May. During the 1944 fiscal year this would mean an increase of 2,688 through graduation before the scheduled date and an increase of 7,430 through the reduction of training courses.

Flight engineers: If the present program were followed there would be a surplus in the number of flight engineers at the beginning of the fiscal year 1944, but at the end of fiscal year 1944 a shortage of 1,123 flight engineers would arise. This shortage was to be replenished by class B Primary Flight Enlisted Trainees (special class).

Aircraft maintenance personnel: Through the execution of the present program, a 100 percent replenishment of aircraft maintenance personnel could be expected in May 1945. However, the ratio between the graduates of ordinary course aircraft maintenance enlisted trainees and advanced course aircraft maintenance enlisted trainees would be 11 to 3, and aircraft maintenance capacity would be decreased. Therefore, beside the previously established plan, three

--7--

training air groups were to be newly established. Their ratio of 5 to 4 would be maintained at the beginning of fiscal year 1945 by appropriating the surplus training facilities of ordinary course aircraft maintenance enlisted trainees for training advanced course aircraft maintenance enlisted trainees as well as the capacities of the newly established training groups.

The number of specialists required to be maintained to meet the Navy General Staff's request by the end of the fiscal year 1943 was 34,017 and by the end of 1944 was 80,650. In accordance with the present program, the number of personnel to be increased during the fiscal year 1943 was 8,435 and during 1944 was 46,890. There was no further increase planned in accordance with the new program. Under the circumstances, the number of specialists was to be 57 percent or 14,322 men short of the Navy General Staff's requests. Non-specialists to meet the Navy General Staff's request were 52,178 at the end of the fiscal year 1943 and 141,410 at the end of the fiscal year 1944.

Equipment maintenance personnel: The six months' training course for ordinary equipment maintenance personnel would be reduced to five months. The period of the training course for photographers was to be four months. Moreover, efforts would be made to replenish the personnel by utilizing to full capacity the training air groups provided for in the previously established and present programs in order to effect 100 percent replenishment of equipment maintenance personnel in June 1945.

--8--

The number of specialists required to be maintained to meet the Navy General Staff's request at the end of the 1943 fiscal year was 13,929 and at the end of 1944 fiscal year it was 31,336. The number of personnel to be increased was 3,459 for the fiscal year

1943 and 12,550 during the fiscal year 1944. There were to be no personnel increased during 1943, but an increase of 7,125 during 1944 for the new program. This would mean that 48.3 percent of the personnel required by the Navy General Staff's request would be trained during the fiscal year 1943 and 78.7 percent during the fiscal year 1944. It was impossible to shorten the course further to increase the number of personnel. This left no alternative but to replenish the shortage of specialists by non-specialists. At the same time, the number of non-specialists required by the Navy General Staff's request was 5,154 during the fiscal year 1943, and 14,567 during the fiscal year 1944.

The principal matters necessary for the execution of this program requiring the careful consideration and cooperation of all Departments of the Navy and the Army were as follows:

Material and manpower: In order to cope with the personnel, technique, and construction capacity requirements, the extensive transfer and cooperation of the capacity of the Navy Technical Department was necessary.

This program was formulated under the condition that some priority would be given to the Navy air war preparations over the

--9--

Army air war preparations. Out of the 30,200 planes requested by the Navy General Staff, 4,300 were to be manufactured in the fiscal year 1944 by facilities to be transferred from the Army. For this purpose it was necessary to discuss and arrange with the Army for its limit of plane production at the present level. (13,000 planes were estimated for the fiscal year 1944.) Otherwise, there was little prospect of producing even 26,000 planes.

The most serious handicap in aircraft production was the shortage of materials. Besides the supply of materials in 1943 being insufficient, the production plan was pushed ahead by two months. Furthermore, since this program in the fiscal year 1944 aimed at increasing production twofold from that of the plan in the preceding year, it was absolutely necessary to obtain the materials at an average of six months in advance. At the same time, it was necessary to obtain part of the supply of materials for 1944 without delay. For this reason, a decision had to be made immediately as to whether or not this program would be followed. If so, the following items had to be decided upon immediately:

1. Institution of wartime special regulations for the aircraft industry.

2. Priority for the supply of metal machine tools and industrial manufacturing machines.

3. The necessary number of technicians and workers.

4. Priority use of the electric power, motive power, transport and billeting facilities.

--10--

Training of personnel: The bottleneck in training flight personnel emanated from inadequate training equipment. For this reason, should the production of aircraft be behind schedule or the aircraft be diverted in excess of the prearranged program to the use of units committed in operations, the number of trained flight personnel would obviously be reduced.

The greatest bottleneck in training maintenance personnel was the shortage of personnel detailed to train in maintenance. The following matters, therefore, had to be settled immediately:

Revision of the Army-Navy Agreement concerning the personnel detailed for training to ensure the necessary number of personnel.

The establishment of the maintenance branch primary enlisted trainee system required to be studied and efforts exerted for its realization.

Stores Bureau

The quantity of aviation fuel produced for the fiscal year 1945 was to be fixed at 1,800,000 kilolitres. (The goal presently to be achieved according to the Fifth Program was 1,200,000 kilolitres.) every possible measure was to be taken to obtain this objective. For this purpose, the quantity of heavy oil, ordinary gasoline and kerosene light oil to be obtained would inevitably be reduced.

Should the fulfillment of the various necessary conditions be impossible, a secondary plan for production of 1,500,000 kilolitres

--11--

of aviation gasoline in the fiscal year 1945 was to be prepared as a supplement.

The production of 15,000,000 kilolitres of crude oil in both Japan Proper and the Southern Area was to be aimed at in 1945.

The quantity of oil to be shipped from the Southern Area was fixed as follows:

Crude oil: Approx. 6,300,000 kilolitres

Refined oil: Approx. 3,550,000 kilolitres

Total: Approx. 9,850,000 kilolitres

The distilling capacity of crude oil and manufacturing capacity of issooctane and other oil was to be increased to handle the above output by expanding the installations.

The allotment of steel was as follows:

1943: Approx. 280,000 tons

1944: Approx. 300,000 tons

Approximately half the necessary man hours to be assigned to the Navy Technical Department for fuel production was:

Fiscal year 1943: Approx. 14,000,000 man hours

Fiscal year 1944: Approx. 15,000,000 man hours

Personnel was to be increased as follows:

Fiscal year 1943: 34,780 men

Fiscal year 1944: 38,600 men

Since aviation gasoline required for the maintenance and operation of the air strength of 14,546 planes from the beginning of the fiscal year 1945, as proposed by the Navy General Staff, was estimated

--12--

at 2,300,000 kilolitres a year, the amount requested by the Navy General Staff was 1,800,000 kilolitres or about 78 percent.

Navy Technical Department

The plan of the Navy Technical Department was based on the diagram of 25 July 1943, showing the second phase war preparations with the continuing armament and war preparations plan. Although reservations were made relative to suspension and deferment of construction of aircraft carriers, no decision was made on the final disposition of these matters. On the other hand, despite the request for large-scale construction of transports, landing craft, motor torpedo and miscellaneous boats, a drastic cut of necessary materials was anticipated.

In addition, the new plan of the Navy Aeronautical Department presupposed the extensive transfer of the capacity of the Navy Technical Department, but its extent and the details were unknown.

The Stores Bureau's plan also presupposed 14,000,000 to 15,000,000 man hours for a year to be allotted to the Navy Technical Department, but concrete details were unknown.

In regard to rapid reinforcement of the inner and the outer combat forces, establishment of the goal for manufacturing weapons to replenish equipment was still impossible.

As mentioned above, there were many basic factors requiring further study, so that it was impossible to report on a plan immediately. The allocation of materials had to be announced as quickly

--13--

as possible and the requests of each department or bureau to the Navy Technical Department had to be adjusted and decided.

Navy Civil Engineering Department

There were many impediments to the materialization of the Navy General Staff's War Preparations Plan in this department. Construction materials were in extremely short supply. This together with the shortage of personnel, developed a severe bottleneck in the realization of the plan. Immediate drastic revisions in the allotment of material were necessary and every effort was made to secure the required quantity,

The ratio of allocation to requirement of construction materials during the fiscal year 1943 did not exceed 36 percent for steel, 52 percent for cement or 41 percent for lumber. In the fiscal year 1944, taking into account the land defense and air armament plans currently being proposed by the Navy General Staff, and the land and sea defense programs already underway, the quantity of critical construction materials required for that year was enormous. The ratio of actual allocation of materials to requirements in 1944 could not exceed 25 percent for steel, 46 percent for cement or 60 percent for timber if the actual supply remained the same as the previous year's level.

Organization, Equipment and Capacity of Construction Units

In view of the fact that there was an acute shortage of personnel for appointment as commanders of construction units, and very

--14--

little time for training probationary technical officers (the training of the second group of junior technical officers was slated for completion about August 1944) and that there was also difficulty in obtaining workers, it was expected that the maximum number of construction units which could be organized during the 1944 fiscal year would be 30. This was assuming that the procurement of drafted workers would continue to be a difficult as it had proven during 1943. Even if steps were taken to increase the labor draft and construction of part of the Homeland installations was postponed, no more than 35 units could be organized yearly. This would fill approximately one-third of the Navy General Staff's request for the maintenance of 50 units in the fiscal year 1943, and 100 units in both 1944 and 1945.

It was planned to organize one construction unit in September 1943, three units in October, four units in November and four units each month thereafter. It was found, however, that the organization of four units during and after January 1944 was not feasible and that it would be necessary to take drastic measures to acquire personnel.

Due to the shortage of unit commanders, it was planned to send three of the 12 units to be organized during September-December as reinforcements to construction units already deployed, while three others were to be included in the Special Civil Engineering Depot.

The output of machinery gradually got under way. With the exception of some machine tools, production reached a monthly level sufficient to equip four unit of "D" class organization, that is,

--15--

half their full quota of equipment and capable of constructing an airfield in about 20 days. It was expected that the machinery output would be further increased during and after April 1944. Despite this increase, however, it would still be difficult to meet the equipment requirements of the construction units. As top priority was being given to the front lines in the allocation of supplies, it appeared that either allocation to the front lines would have to be cut* or the number of units reduced, if the construction units were to be fully equipped.

Maintenance Plans for Construction Units

Materials for construction units had previously been supplied by diverting materials allocated for general construction. This system could no longer be continued and it became imperative to make definite allocations for construction units from the beginning of the 1944 fiscal year.

Since personnel for construction units feel outside the purview of the National Mobilization Program, it was recommended that such drastic measures be used as mobilizing Koreans and Formosans, lowering the age for conscription and the suspension of students in schools of higher education.

With a view toward raising the potentiality of construction units it was considered imperative that the following matters be decided immediately.

--16--

1. Competent personnel be assigned as unit commanders.

2. Plans be instituted whereby enlisted personnel, under the technical civil engineering personnel system, be promoted to technical officer rank.

3. About half the strength of construction units be composed of civil engineering technical personnel and constructions units be considered combat units.

4. Units be trained for a minimum of two months before departure from Japan.

Personnel Bureau

In order that the personnel requirements under this plan might be fulfilled, it was necessary to recruit an additional 1,087,000 men to fill the shortage expected at the end of the 1944 fiscal year, in excess of the 205,000 personnel to be recruited under the Army-Navy Agreement for the same fiscal year.

Personnel Requirements under this plan as compared with actual personnel allotted was as follows:

--17--

Classification

End of
1943
Fiscal
Year

End of
1944
Fiscal
Year

End of
1945
Fiscal
Year

Remarks

Wartime Personnel Requirement

848,640

1,717,772

2,174,391

1. The figures for the 1944 fiscal year and onward did not include the number of recruits.

2. Wartime personnel requirements were set at 145 per cent of service complement.

Actual Personnel

633,646

630,982

542,444

Shortage

214,994

1,086,790

1,631,47

Preparations were under way for the recruitment of 68,000 volunteers during the 1944 fiscal year. It was recommended that this figure be increased to 100,000.

After due study, it was felt that this increase could be accomplished during the 1944 fiscal year in the following manner:

1. Increasing the conscription quota for active service personnel. The age of those liable for conscription was to be lowered by one year in order that the greatest number possible might be called into service between 1 December 1944 and March 1945. It was expected that by this method personnel strength would be increased by 150,000 in addition to the goal established by the Joint Army-Navy Agreement.

As a result of lowering the age of persons liable for conscription, it was expected that 1,200,000 men liable for active service and reserves, plus 2,400,000 of the Second Militia would be called into service in the Army and Navy during the two-year period from

--18--

the end of 1943 to the end of 1945. Of these, it was assumed that 150,000 would be called during the latter part of the 1944 fiscal year.

2. Approximately 300,000 of the 1,500,000 members of the former Second Militia were to be called into service in the Navy.

It seemed reasonable to expect that the maximum possible increase of personnel strength for the 1944 fiscal year would be 550,000. This figure coincided with the figure set for increases in personnel strength under the Revised Fifth War Preparations Plans.

Inasmuch as meeting the personnel requirements mentioned above was Considered to be very difficult, it was considered impossible to recruit the additional 1,087,000 men required to fulfill this plan, both from the standpoint of manpower mobilization and the inadequacy of training facilities. Under the condition existing, it was recommended that priorities be set on the allocation of manpower, while, at the same time, economy of personnel be practiced to the utmost and the activation of units not urgently needed be postponed. At the same time, the need was recognized for urgent measures to meet the personnel requirements set forth in the Revised Fifth War Preparation Plan by conscripting recruits and providing training facilities for such personnel.

Emergency measures for repletion of the ranks of officers, reserve officers, special duty officers and warrant officers were to be instituted separately, after the above policy had been established

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Education Bureau

Priority was to be given to the education of aeronautical personnel; however, the education of general personnel was to be accelerated in closer coordination with the aeronautical education program.

The greatest stress was placed on maintaining and improving the fighting potential of operational units. Replacement of personnel, therefore, for the purpose of their education was kept to a minimum. Since universal high grade education was impossible, the principle of maintaining crack outfits was to be followed.

It was maintained that the training of operational units should be conducted in the field by dispatching guidance personnel who would institute short training courses.

Since definite figures had not been established for either personnel strength or specialists, a concrete statement of views could not be made on the execution of the plan. The following, however, gives an indication of the difficulties which had to be met and overcome:

Due to the inadequacy of educational facilities, officers and men from the guard and defense units were used as instructors for the ordinary courses of the Gunnery (AA) School and Naval Mine School,

The education period had been shortened to a minimum. It was considered that no further shortening of the courses was possible

--20--

unless radical changes were adopted in regard to teaching material, equipment and instructors. Night instruction, as well as Saturday and holiday classes, was in effect and the elimination of a winter vacation for officer candidate colleges was planned.

During the 1944 fiscal year, the merit graduation system (a system of graduating students as soon as they attained the required standard, even before the close of the regular term) which had been in effect in the Communication School, was to be extended and intensified. By this means, it was expected that the number of graduates would be increased by approximately 20 percent.

Prior to this, various officer candidate colleges had hesitated to graduate students prior to the completion of a term as the curriculum in those colleges consisted of basic subjects. With the worsening of the war situation, however, concrete plans to expedite the graduation of students were considered.

The shortage and deterioration in quality of instructors, as well as the lack of teaching materials, caused serious bottlenecks in the education program. Better cooperation of the various authorities concerned was urged to overcome this situation.

It was recommended that, in view of the lack of transportation facilities, new recruits be given education in the ordinary courses immediately upon completion of the basic training course. Where this proved impossible, plans were under survey whereby the deficit

--21--

could be overcome by intensification of field training and through the existing system of qualifying personnel by examination.

Military Preparation Bureau

According to a draft drawn up by the Cabinet Planning Board on 27 August 1943 in regard to the General Outline of the Materials Mobilization Plan for the 1944 fiscal year, materials would be available for construction of 1,050,000 tons of cargo ships (1,400,000 tons with tanker and other types of vessels included) and 430,000 tons of wooden cargo vessels (500,000 tons with other types of wooden vessels included). On that basis, the total transport capacity for Army, Navy and civilian use would be 60,860,000 tons a year, or a decrease of 327,000 tons in transport capacity as compared with the 1943 fiscal year. when the new requirements were received from the Supreme Command for an additional requisitioning of 360,000 tons of shipping, therefore, a sharp production increase was urged. A tentative plan was devised by the Cabinet Planning Board after reexamining the draft previously drawn up after joint study by the Army and Navy (HI Study), The new plan called for:

Steel Ship Construction

1,800,000 tons (of which 1,350,000 tons were cargo vessels)

Total transport capacity required: 47,000,000 tons. This was a 17,000,000 tons increase as compared with the draft of the General Outline

Wooden Ship Construction

400,000 tons

Ordinary Steel Supply

5,100,000 tons

Aircraft Production

Total Army and Navy: 30,000 planes

--22--

To meet these requirements, it was necessary to attain at least a 2,000,000 ton level for steel ship construction, 5,500,000 ton level for ordinary steel supply and 40,000 tons for aircraft production for the Army and Navy. However, with the limited resources of the country, it was deemed impossible to attain these goals.

In order to secure the supply of materials necessary to meet the goals set by the "HI" Study for the fiscal year 1944, based on the supply distribution basis reached by the Cabinet Planning Board, it was imperative that the production of iron, coal, aluminum and copper be boosted. Under these circumstances, it was necessary to limit the allocation of top priorities to munition industries. If a disproportionately large amount of material was allocated to munitions, the capacity to meet supply requirements in other directions would drop sharply, resulting in the nation's inability to secure the required power for a counterattack.

It was considered difficult in the allocating of supplies between the Army and Navy to raise the ratio for the Navy any higher than its 1943 ratio, unless a special operational agreement was negotiated.

In allocating supplies to the Navy, priority was given to naval aircraft production. Efforts were made to reach a goal of 26,000 planes during the fiscal year 1944 and to bring the supply of fuel up to meet the requirements of the aircraft produced. It was realized, however, that should allocations be made according to the foregoing priority system, it would be impossible to execute plans which

--23--

would meet the requirements of the established armament program of the Third Phase Operation of the Navy.

It was deemed necessary that insofar as aircraft were concerned, an operational agreement be concluded that would enable the execution plans based on the allocation of supplies in the ratio of two for the Navy and one for the Army. This would mean 20,000 planes for the Naval and 10,000 planes for the Army.

Steel ship construction for the 1945 fiscal year should be held to the level of the 1944 fiscal year — 1,800,000 tons. Thus, about 250,000 tons of the 550,000 tons of the advance allocation of steel for the 1944 fiscal year's ship construction were to be set aside and allocated at the ratio of two to one.

Allocation of materials for war preparations, other than aircraft, were to be set at the same ratio between Army and Navy as existed during 1943.

It was considered that further reduction of supplies for civilian consumption would be difficult. Actually, it was considered necessary to increase allocations in this category.

Adoption of these measures would have enabled the production of approximately 20,000 planes as well as about one- half of the planned output of naval vessels for the revised Fifth Plan. Meanwhile, in view of the fact that stockpiles of war preparation stocks and running stocks were being dissipated, it was important that the various executive departments concerned institute policies whereby clear

--24--

directives would be issued on the execution of war preparations plans devised for the most effective use of critical materials and war preparations be conducted on the basis of a priority system.

Labor

The Empire was faced with the urgent need to mobilize a labor force of 1,800,000 workers. Inasmuch as the majority of the persons remaining as a potential source for the labor force fell into the classification of deformed, disabled or feeble persons, it was difficult to mobilize more than 1,000,000 workers (including 300,000 females) under the current system. To secure the required number, therefore, there was no alternative but to resort to emergency measures. These measures included:

Increasing the mobilization of women to a total labor draft of 1,300,000.

Elimination of all schools not conforming to the provisions of the School Ordinance of the Education Ministry. From this source they would be able to obtain:

Males

50,000

Females

50,000

Total

100,000

Temporary closure of certain schools conforming to provisions of the School Ordinance of the Education Ministry. Students of liberal arts in institutions of higher education would yield:

--25--

Males

100,000

Females

10,000

Total

110,000

Students in the last year of second schools:

Males

160,000

Females

160,000

Total

320,000

It was believed that a total of 1,830,000 people would be obtained from these sources.

In view of the foregoing, the success or failure of the armament program for the 1944 fiscal year depended primarily on increasing and maintaining the transportation capacity at least at the level proposed in the "HI" Study.

Since the carrying out of these measures was the direct responsibility of the Navy, it was important that the Navy's position in such matters as production and the strengthening of national power be recognized. The completion of the above armament program depended on the overcoming of many difficulties in the political, economic and industrial fields. Under the circumstances, it was essential that unity be achieved between the Army and Navy, as well as between the armed services, the government and the people.

During the conference for the study of war preparations a great many contradictions were found in the reports of the different executive departments. There was a good deal of exaggeration, as was

--26--

more or less the case with most formal conferences at that time, caused by wishful thinking. For example, in drafting its plan for the construction of 30,200 aircraft, the Navy Aeronautical Department counted on the Army factories to produce 4,000 aircraft. Even the remaining 26,000 included several thousand which depended directly on supplies, as well as technical and manpower assistance from the Navy Technical Department as a condition of production. Also, the aviation fuel production plan of the Stores Bureau was based on the large-scale use of the production facilities of the Navy Technical Department, without having ascertained if these facilities were available. It was found that all plans devised by executive departments were based, to no small degree, on wishful thinking and arbitrary assumptions. Especially was this true in regard to the allocation of materials, the mobilization of manpower and the estimates of national strength.

In the early part of September 1943, the Supreme Command issued a demand requisition for 360,000 tons of vessels (plus tonnage to cover monthly losses) which it stated was to be used to restore trans-port and supply capacity hit by the loss of vessels in the Solomon Islands area and other theaters of operation. This was considered necessary to turn the tide of war. Officers in charge of the Army, Navy, Cabinet Planning Board, Ministry of Commerce and Industry and General Maritime Bureau conducted a joint study on the subject, which lasted ten days. This study became known as the "HI" Study. The

--27--

results of this study shoved a marked decrease in national strength. This was particularly true in the case of munitions production. It was reported that the situation in regard to munitions production was such that even if all possible emergency measures were taken, the war situation improved and the transport capacity developed along satisfactory lines, the figures given below would represent the maximum production possible. These figures were approved at the 27 September 1943 meeting of the Liaison Conference of the Government and Imperial General Headquarters. At the same time, approval was given to the proposal to reduce the ship tonnage requisitioned for Army and Navy to 250,000 tons with a monthly replacement up to 35,000 tons to compensate for operational shipping losses.

The 1944 goals decided for munitions production were:

Aircraft

40,000 planes

Aluminum

210,000 tons

Special steel

1,000,000 tons

Ordinary steel materials

5,000,000 tons

Electrolytic copper

150,000 tons

Steel Ship Construction

1,800,000 gross tons

Wooden Ship Construction

1400,000 gross tons

When this program was approved, the difficulty of its execution was repeatedly stressed by both the President of the Planning Board and the Minister of Commerce and Industry. On that occasion, the Supreme Command of the Army called for the allocation of 25,000 airplanes as against the 30,000 requested by the Navy General Staff.

--28--

This made a total of 55,000 planes, as against the 40,000 set as the production target. Serious controversies were expected as at the conference of the Naval War Preparations Research Committee, the Chief of the Military Preparation Bureau had contended in his report that the key to materializing the Third Phase War Preparations was to allocate aircraft production for the Navy and Army in the ratio of 2 to 1. He also stated that, even if such items as aluminum and special steel were to be distributed at this ratio (to which the Army was most unlikely to agree) it would be more effective for the maintenance of the overall war potentiality of Japan to adjust the number of airplanes actually produced at 30,000, of which 20,000 should go to the Navy and 10,000 to the Army.

Tentative Compromise Plan Proposed by the Navy Affairs Bureau ("HI" Study)

In view of the controversies between the departments, the Navy Affairs Bureau keenly felt the need for unifying ideas; in the Navy and promptly presented a tentative plan. It was felt that the view taken by the Military Preparation Bureau was the most impartial and correct from the standpoint of national power. Meanwhile, an inspection which was being conducted for increasing aircraft production, with Mr. Ginjiro Fujiwara as administrative inspector, brought hopes that by enforcing measures to improve production management, technique and economy of materials, it would be possible to attain some

--29--

increase in production. The Navy Affairs Bureau, therefore, adopted a new 23,000 planes plan as against the 26,000 plan called for by the Navy General Staff. At the same time, the Bureau attempted to obtain part of the production capacity and materials of the Army through unified efforts of the Navy Ministry and Naval General Staff. The contents of the proposal, which was confined to matters relating to the Navy Aeronautical Department and the Navy Ship and Ordnance Department, were as follows:

26 September 1943

First Section, Navy Affairs Bureau

Adjustment plan for the Third Phase Military

Preparations (for the Navy Technical Department and the Navy Aeronautical Department only)

In view of the present war situation we have made the following modification of the program. It is desired that the modified plan be fully executed at all costs.

The Navy Aeronautical Department

Aircraft production for 1943 fiscal year will be revised to not less than 10,000.

The aircraft production goal for 1944 fiscal year will be revised to 23,000, and this production plan will be promptly effected. For this purpose, the Navy Technical Department will cooperate with the Navy Aeronautical Department through a large scale transfer to the latter of personnel, techniques, materials and production facilities. At the same time, the priority given to the strength will be reconfirmed and thoroughly practiced by the whole Navy.

Note: 1. With the progress of the present negotiations on the aircraft agreement between the Navy and the Army, measures will be taken to incorporate successively successful agreements as an addition to the plan.

--30--

2. Although it is extremely difficult, under the present conditions, to meet fully additional demands for materials within the present fiscal year, all possible efforts will be exerted to satisfy the requirement.

The Navy Technical Department

In the 1943 fiscal year, maximum efforts will be exerted for pushing the established plan.

The production goal for 1944 fiscal year will be promptly reduced so as to meet the supply of approximately 400,000 tons of steel. Utmost efforts will be exerted to accelerate the execution of these measures through utilization of all the materials remaining from the previous fiscal year and through acquisition beforehand of materials. At the same time, more exhaustive measures will be taken for the standardization of vessel types, an improvement in the quality of parts, and the thorough execution of the priority system.

The Navy Aeronautical Department withheld commenting on this compromise plan formulated by the Navy Affairs Bureau pending publication of the findings of the administrative inspection by Mr. Fujiwara, as the Department expected this report to show prospects of improvement in the situation.

The Navy General Staff, on the other hand, was adamant in its opposition to decreasing aircraft production by 3,000 planes and refused to listen to the reasons for the reduction. Under the circumstances, the Navy Ministry was compelled to refrain from establishing a definite goal. In the end, even though the Navy Ministry did not accept the 26,000 plane goal, it decided upon a general policy of giving top priority to aircraft production in order that the greatest number of planes would be produced in the shortest possible time.

--31--

Meanwhile, it attempted to bring about the cooperation of the Navy Aeronautical Department and the Stores Bureau with the Navy Technical Department. It was also decided that efforts would be made to exploit the results of the current administrative inspection with a view to transferring production capacity from the Army.

Negotiations with the Army in Regard to Allocation of Materials and Production Facilities for Aircraft Production

The aluminum production goal of 210,000 tons set by the "HI" Study proved to be a production bottleneck, limiting the aircraft production goal for the 1944 fiscal year to 40,000 planes. It was feared that, should the standing principle of equal allocation to the Army and Navy be followed, naval aircraft production would be held to a level of 20,000 planes. For that reason, the Navy took the view that the minimum as proposed by the Military Preparations Bureau, which allotted twice the amount of material to the Navy as to the Army, was necessary and that operational requirements called for 30,200 aircraft. This figure included 26,000 as the minimum production goal, plus the hoped for increased production of 4,000 planes which would result from the current administrative inspection.

It was unanimously agreed that, armed with the necessary operational, administrative and theoretical data, the Chief of the Naval General Staff and the Minister of the Navy, together with their staffs, would, as a unit, push negotiations with the Army to obtain

--32--

approval of these proposals. Bitter arguments ensued during September and October, but the Army remained adamant in refusing to accept the Navy's proposals. In the end, not even a procedural agreement was reached. Finally, it was decided between the Army and Navy Minsters that the standing allocation ratio of equal distribution to the Army and Navy would remain in effect.

Studies made at this time showed that, on an average, the aluminum consumption per plane was 5.3 tons for the Army and 5.7 tons for the Navy. This would mean that, should the above distribution be made, the production of naval aircraft would fall short of that for the Army.

In order to attain the desired production goal, therefore, the Navy Ministry was forced to rely upon drawing stores from warehouses, improvement of production techniques and the diversion of production facilities from the Navy Technical Department. In practice, however, it was difficult to transfer the personnel and facilities of the Navy Technical Department due to long standing traditions and prerogatives of both departments.

Interim Decisions

With the failure of the above negotiations, the Navy Affairs Bureau was forced to propose that the Third Phase Preparations be started under the conditions set forth below. This procedure was, at the same time, approved by the Emergency War Preparations Acceleration Department.

--33--

1. The concentrated efforts of the entire Navy were to aim at producing 9,818 (commonly given as 10,000) planes for the 1943 fiscal year, and 25,905 (commonly given as 26,000) planes for the 1944 fiscal year. This was the goal given in the fundamental plan of the Navy Aeronautical Department, less the output expected from Army facilities.

2. Conditions for achieving the production were:

a. Maximum effort would be exerted for achieving production by requesting the cooperation of the Navy Technical Department.

b. In order to procure raw materials and parts and to improve production technique (especially to reduce waste) highly specialised technical guidance parties were to be organized and dispatched on an itinerant basis.

c. A plan was to be formulated which would provide adequate interchange of personnel between the Navy Technical Department and the Navy Aeronautical Department. The plan would be based on the new organization and personnel assignments of the two departments.

3. The reduction of naval ship construction, which would inevitably occur with the transfer of production facilities from the Navy Technical Department to the Navy Aeronautical Department was to be accepted.

4. Since the figures given for materials required in the Fuel War Preparations Plan were far too large to hope for early fulfillment, requests for materials, parts and machinery were to be

--34--

presented with more concrete data and the Navy Affairs Bureau was to adjust these requests upon deliberation with the Navy Technical Department and the Stores Bureau.

5. Negotiations with the Army, although they had failed for the time being, were not to be abandoned. Also, efforts were to be made to lessen the deficiencies in war preparations both by attempting to achieve an increase in the actual production of naval planes and by encouraging the cooperation of Army planes in naval operations, through operational negotiations between the Army and the Navy.

These policies were devised at the beginning of 1944.

Problems Related to Administrative Inspection and Munitions Ministry

During September and October 1943, while the Navy was engaged in the study of the Third Phase Armament Program, an administrative inspection of the Japanese aircraft industry was conducted with Mr. Ginjiro Fujiwara as the special inspector. This inspection contributed a great deal to the improvement of plant management, economy of materials, repletion of equipment and technical guidance, especially in casting and forging, in many companies.

The inspection report stated that the production goal of 40,000 planes set in the "HI" Study could be attained, although considerable difficulty would be encountered in producing sufficient engines.

--35--

It also recommended unified control of munitions production, since the deadlock brought about by competition between the Army and Navy, with their excessive variety of aircraft, was hindering the increase in production. The Army and Navy finally agreed to this recommendation and to the transfer of administrative powers in regard to the production of aircraft and related weapons to a General Air Ordnance Bureau to be established in the Munitions Ministry. They further agreed to support the bureau by sending to it their personnel records.

Some doubt was entertained by administrative authorities of the Navy as to whether the Navy Minister should be relieved of the final responsibility for munitions production at this crucial stage in war preparations. They also felt that such a drastic change in administration might cause a decrease in production. Despite these apprehensions, however, the Navy could not oppose the plan formed on the findings of the administrative inspection since it had no concrete substitute plan to offer. Measures were, therefore, taken to activate the new organization at the end of November 1943 and transfers were completed by 15 January 1944. The enforcement of these measures proceeded with comparative ease as far as the establishment within the Munitions Ministry of the General Air Ordnance Bureau in which the Army, Navy and civilians were duly represented.

--36--

Execution Plan and Outline of its Progress

The formulation of the Third Phase War Preparation Plan was the most difficult program ever undertaken by the Navy in peacetime or in wartime, since it was drawn up at a time when the war situation had taken a decided turn for the worse. Moreover, the plan itself contained many transitional elements which were subject to change in the future. This, naturally, had many disadvantages, particularly in the enforcement of the shipbuilding program, which had to be spread over a longer period of time than the aircraft program. The effect of the "aircraft first" policy had a considerable effect on the shipbuilding plan. However, this program, known as the Third Phase War Preparation Program, remained as the backbone of the Japanese Naval War Preparation Plan until almost the end of the war. It was revised in the last phase of the war following a change of policy calling for an increase in special attack weapons.

The outline of the Final War Preparations Program and its enforcement was as follows:

Shipbuilding Program

Naval vessels newly added to the existing shipbuilding plan in 1943 and 1944 to be begun in 1944 and 1945 were as shown on Chart 1. Government appropriations approved by the Diet for these additional vessels were:

--37--

1944 fiscal year

¥ 2,186,709,000

1945 fiscal year

¥ 539,225,000

Further vessels were added in 1944 to those listed in Chart 1 as part of the wartime shipbuilding program for 1945 fiscal year. These were as shown on Chart 2. Actual construction of naval vessels in 1943 and 1944 fiscal years based upon all prearranged programs was completed as shown on Chart 3.

Ships that were dropped from the construction program before or during construction are shown below:

Type of Ship

Program

No of
Ships on
Construction
Program

No of
Ships
Cancelled

No of Ships
Construction
Suspended

Cruiser (B)

Revised 5

2

2

Aircraft Carrier

Emergency

1

1

The IBUKI, Converted from a cruiser.

Revised 5

18

13

2

Seaplane tender

Emergency

1

1

Revised 5

3

3

Emergency net layer

Revised 5

1

1

Submarine tender

Revised 5

3

Destroyer (A)

Emergency

16

8

Revised 5

8

8

Destroyer (B)

Revised 5

23

18

Submarine (A)

Revised 5

6

3

--38--

Chart No 1

Naval Vessels Added to 1943 - 1944 Shipbuilding Plan.

Type of Ship

Number of Ships

Standard Displacement
(ton)

Speed (kt)

Cruising
Range
(kt - nautical
mile)

Main Armament

Remarks

Planned in Fiscal 1943

Planned in Fiscal 1944

Destroyer (D)

8

1,350

27.3

18 - 3,500

12.7cm double mounted gun

1

Improved model of "Matsu"

12.7cm single mounted gun

1

25mm triple mounted machine guns

4

Type 3 torpedo tubes

1

Submarine (D)

7

1,660

13.0 (Surface)

13 - 5,000 (Surface)

25mm triple mounted machine guns

1

Improved model.

Loading capacity 150 tons of light oil.

25mm double mounted machine guns

2

8cm double mounted mortars

2

Submarine (E)

44

1,250

19.5 (Surface)

14 - 16,000 (Surface)

12cm gun

1

New model.

13mm machine guns

2

Torpedo tubes

6

Submarine (High speed)

23

1,000

19.0 (Underwater)

3 - 45 hours (Underwater) according to the speed

25mm single mounted guns

2

New model

High speed while submerged.

Torpedo tubes

4

Submarine Transport

13

370

10.0 (Surface)

10 - 3,000 (Surface)

25mm single mounted guns

1

New model

Escort Ship (A)

21

940

19.5

16 - 5,000

12cm double mounted guns

1

"UKURU" Type

12cm gun

1

25mm double mounted machine guns

2

Depth charges

120

Escort Ship (C)

66

66

745

16.5

14 - 6,500

12cm gun

1

New model

25mm triple mounted machine guns

2

Depth charges

120

Escort Ship (D)

48

99

740

17.5

14 - 4,500

12cm gun

1

New model

25mm triple mounted machine guns

2

Depth charges

120

Special Duty Ship (Special)

22

24

1,500

22.0

18 - 3,700

12.7cm double mounted gun

1

New model

25mm triple mounted machine guns

3

Loading capacity:

Large landing barge

4

Tanks

7

"KORYU" midget submarines

2

"KAITEN" human torpedoes

6

400-500 tons of cargo, or 200-400 personnel

Landing Craft

63

40

950

16.0

14 - 1,700

8cm gun

1

New model

25mm triple mounted machine guns

2

Loading capacity:

7 ton tanks

14

15 ton tanks

9

12.5 ton tanks

7

28.3 ton tanks

5

or 22 ton tanks

4 or 5

Auxiliary Submarine Chaser (Wooden)

100

130

11.0

10 - 1,000

25-mm machine gun

1

No 1 Type

Auxiliary Patrol Boat (Wooden)

62

208

218

7.0

6 - 15 days

25-mm triple mounted machine gun

1

New model

Auxiliary Patrol Boat (Steel)

50 or 70 of the above will be steel vessels

Motor Torpedo Boat (B)

1,580

20

23-34

full speed 300

13mm machine gun

1

New model

Torpedoes

2

Depth charges

6

--39--

Chart No 2

Shipbuilding Program 1945

Type of Ship

Number of Ships

Standard Displacement
(ton)

Speed
(kt) (surface)

Cruising
Range
(kt -
nautical mile)

Main Armament

Remarks

Sumarine (Small)

40

320

10.5

10 - 3,000

7.7mm machine gun

1

New model.

Torpedo tubes

2

Mine Layer

6

3,000

11.0

12cm dual purpose gun

1

Improved model of Type 2-D

25mm triple mounted machine guns

2

25mm double mounted machine guns

2

25mm single mounted machine guns

4

Mines

380

Light Mine Layer

2

720

20.0

14 - 2,000

12cm gun

1

"Ajiro" type

25mm double mounted machine gun

1

Mines

36

Auxiliary Escort Ship (A)

6

280

15.0

12 - 1,500

45mm single mounted machine gun

1

New model (Steel vessel)

25mm single mounted machine guns

6

Depth charge release

4

"Kaiten" human torpedoes

2

Auxiliary Escort Ship (B)

60

280

12.5

10 - 1,500

40mm single mounted machine gun

1

New model (Wooden)

25mm single mounted machine guns

6

Depth charge release

4

"Kaiten" human torpedoes

1

Oil Tanker

4

18,500

16.5

8cm gun

1

Improved model of 1TL Type ship. Loaded with 13,500 tons of oil for supply.

25mm triple mounted machine guns

2

--41--

Chart No 3

Construction of Naval Vessels 1943 - 1944

Year

1943 Fiscal Year

1944 Fiscal Year

Grand Total

Month

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Jan

Feb

Mar

Total

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Jan

Feb

Mar

Total

Type of Ship

Aircraft Carrier

1

1

2

1

1

4

5

" (converted)

1

1

1

1

4

4

Cruiser

1

1

2

1

1

3

Destroyer

2

1

3

1

1

2

1

2

13

1

2

3

1

3

4

1

3

3

4

1

6

32

45

Submarine

3

3

4

4

2

4

3

5

3

5

3

2

41

1

4

2

3

4

4

2

3

5

2

5

2

37

78

Escort Ship

3

1

2

1

1

2

3

1

8

13

35

6

4

4

6

9

10

14

9

17

8

11

12

110

145

Naval Transport (Special)

1

1

3

3

2

3

3

14

15

Landing Craft

2

4

6

2

3

4

4

3

13

5

3

1

3

2

1

44

50

Mine Sweeper

1

1

2

1

1

6

2

1

1

4

10

Submarine Chaser

2

1

1

1

1

4

1

2

3

16

1

1

1

1

4

20

Light Mine Layer

1

1

1

1

2

Special Duty Ship

2

1

1

2

6

1

1

2

8

Auxiliary Patrol Boat

2

4

6

6

Auxiliary Submarine Chaser

8

8

6

6

12

5

11

5

13

4

8

9

95

6

9

10

13

12

10

11

14

7

5

97

192

Auxiliary Mine Sweeper

2

2

2

2

1

9

9

--43--

Submarine (B)

Supplementary

7

Revised 5

32

32

Submarine (C)

Emergency

6

3

Supplementary

5

2

Revised 5

40

40

Submarine (Medium)

Emergency

11

4

Supplementary

15

14

Revised 5

43

43

Submarine (Special)

Revised 5

18

9

Submarine (Auxiliary)

Emergency

3

1

Submarine (E)

Wartime Construction 1944

44

44

Mine sweeper

Emergency

28

17

Revised 5

36

36

Submarine chaser

Emergency

20

1

Revised 5

30

27

Oil tanker

Extraordinary

4

3

Emergency

4

2

Revised 5

15

15

Target ship for bombing

Revised 5

5

3

Icebreaker

Revised 5

1

1

-44--

Store ship

Revised 5

10

10

Repair ship

Revised 5

2

2

Survey ship

Revised 5

1

1

Light Mine layer

Emergency

14

13

Revised 5

12

12

Aircraft Production

It was necessary to produce some 11,500 planes during the 1943 fiscal year and about 30,000 planes during the 1944. fiscal year in order to secure the required operational air strength of 5,876 planes and 14,548 planes at the beginning of the 1944 and 1945 fiscal years, respectively, as demanded by the Naval General Staff and to provide sufficient machines for training. In connection with the above figures, the Aeronautical Department devised a plan calling for 9,818 planes (generally referred to as 10,000 planes) and 25,905 planes (generally referred to as 26,000 planes). With this plan, the Navy made a good start in the production of aircraft. Details of the plan are given below:

Airplane Production Plan under Urgent Program for a Drastic Increase in Air Strength

Fiscal Year

Type of Planes

1943

1944

Class A Fighters Zero Fighter

2,890

4,105

Carrier Fighter Type 17, Experimental

650

--45--

Class-B Fighters

Interceptor Mitsubishi No 14 Experimental

540

1,575

Interceptor Kawanishi No 1

260

450

Interceptor Kawanishi No 1 Improved

1,920

Interceptor Nakajima No 18 Experimental

75

Class-C Fighters

Land Reconnaissance Plane Type 2

220

1,500

Twin-engined Bomber Type 15 Experimental

160

Carrier Borne Bomber and Attack Plane

Carrier Bomber Type 99

600

530

Carrier Attack Plane Type 97

250

Carrier Bomber Type 13 Experimental

460

2,055

Carrier Attack Plane Type 14 Experimental

460

810

Carrier Attack Plane Type 16 Experimental

70

675

Carrier (Land) Reconnaissance Plane

Carrier Reconnaissance Plane Type 2

130

330

Carrier Reconnaissance Plane Nakajima No 17 Experimental

640

Land Bomber

Twin-engined Bomber Type 15 Experimental

135

1,500

Land Attack Plane

Land Attack Plane Type 1

785

1,375

Submarine Attack Plane

100

Reconnaissance Seaplane

Observation Seaplane Type Zero

460

120

--46--

Seaplane Bomber Type 14 Experimental

65

780

Reconnaissance Seaplane Type Zero

430

450

High Speed Reconnaissance Seaplane Type 14, Experimental

17

Seaplane Fighter

Seaplane Fighter Kawanishi No 15 Experimental

103

Patrol Plane

Patrol Plane Type 17 Experimental

450

Submarine
Reconnaissance
Plane

Reconnaissance Seaplane Type Zero Small

70

Training Bomber

Training Bomber Type 2

81

130

Transport Plane

Transport Plane Type Zero

72

525

Training Planes

1,650

5,000

Total:

9,818

25,905

After the Third Phase War Preparations Plan was initiated, the production of aircraft attained remarkable results. Particularly during the 1943 fiscal year extremely favorable progress was made. The monthly aircraft production gradually increased until the long-awaited goal of 1,100 planes monthly was surpassed in March 1944 and the total annual production reached 9,481 planes. From the beginning of 1944, however, little increase was shown in production.

The monthly production rate kept fluctuating between the 1,100 and 1,200 levels, which was far below the increases calculated in the program. The monthly output dropped to around 1,000 planes

--47--

after December 1944, due to enemy air raids on the Homeland and the commencement of the manufacture of planes for special purposes. This resulted in the drop of total annual output to 13,479 planes, only 50 percent of the goal for that year.

The Munitions Ministry might have ascribed this failure in the Emergency Production Program to numerous disadvantages involving machines, facilities, materials, technique or labor. However, the Navy, while admitting the inevitability of the production drop from the latter part of that year, nevertheless attributed the failure in the earlier period mainly to the excessive expansion of facilities by the entrepreneurs under the pretext of a shortage in plant capacity, and to the resultant dispersion of technical facilities.

Chart 4 indicates the actual aircraft production, classified by type of plane, in the 1943 and 1944 fiscal years.

Note: This table covers, for the sake of reference, not only the above-mentioned two years, but also other war years.

--48--

Chart No 4

Actual Aircraft Production (Monthly and Quarterly) for 1943 and 1944, also figures for 1941, 1942 and 1945 fiscal year.

Aircraft

1941
(Dec-Mar)

1942

1943

194

1945
(up to Aug)

Grand

Total

I

II

III

IV

Total

I

II

III

IV

Total

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Jan

Feb

Mar

Apr

Way

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Jan

Feb

Mar

Standard Planes

Carrier Fighter

315

1,691

217

221

223

230

241

336

285

312

399

363

269

362

3416

339

327

300

278

367

244

339

360

268

251

167

247

3487

1014

9923

663

807

952

994

966

889

967

665

Interceptor

1

13

2

2

3

8

11

27

35

37

42

35

67

79

344

117

58

116

127

117

125

128

121

95

89

97

140

1331

337

2026

7

46

114

177

291

369

345

326

Night Fighter

0

54

10

11

12

8

7

12

18

22

22

25

18

18

183

35

40

40

27

35

40

23

0

0

0

0

0

240

0

477

33

27

62

61

115

102

23

0

Carrier Bomber

81

271

43

53

64

72

79

82

99

114

132

140

147

141

1167

125

133

118

107

106

122

116

133

150

115

98

101

1424

246

3189

162

233

344

428

376

335

399

314

Carrier Attack Plane

0

113

27

39

35

36

48

29

34

40

34

30

25

39

412

36

36

57

79

85

76

96

87

60

75

83

94

864

133

1522

97

113

108

94

129

240

243

252

Land Reconnaissance Plane

0

0

0

0

0

0

0

0

0

2

2

1

2

6

13

6

0

1

4

8

19

25

26

25

30

38

64

246

204

463

0

0

4

9

7

31

76

132

Land Bomber

0

0

0

0

0

0

2

4

4

10

25

11

20

39

111

46

46

51

47

48

69

75

88

84

90

52

52

748

240

1099

0

6

39

66

143

164

247

194

Land Attack Plane

219

672

56

55

57

58

57

56

93

57

63

53

50

661

73

70

79

89

85

91

109

108

60

55

60

90

929

122

2603

168

171

173

149

222

265

277

165

Patrol Plane

0

0

0

0

0

0

0

1

0

1

1

1

1

2

7

1

2

3

3

3

3

8

11

14

16

11

13

88

58

193

0

1

2

4

6

9

33

40

Land Transport Plane

30

91

6

6

6

0

5

5

3

5

5

8

14

15

77

3

3

17

14

16

19

20

16

17

19

9

21

174

40

412

17

10

13

37

23

49

53

49

Seaplane Fighter

0

183

25

22

20

12

8

82

11

13

15

9

10

10

237

0

0

0

0

0

a

0

0

0

0

0

0

0

0

420

67

102

39

29

0

0

0

0

Reconnaissance Seaplane

27

272

35

38

28

44

49

41

44

45

45

51

49

51

520

53

53

62

52

59

40

601

70

73

49

47

32

651

97

1527

101

134

134

151

168

151

204

128

Observation Seaplane

19

218

28

32

19

20

27

40

48

50

50

50

40

35

439

30

39

30

19

6

0

0

0

0

0

0

0

116

0

792

79

87

148

125

95

21

0

0

Seaplane Bomber

0

0

0

0

0

0

0

0

1

0

0

0

1

0

2

0

0

2

1

1

1

2

1

1

1

2

2

14

11

27

0

0

1

1

2

3

4

5

--49--

Chart No 4

Actual Aircraft Production (Monthly and Quarterly) for 1943 and 1944, also figures for 1941, 1942, and 1945 fiscal years (Cont'd)

Type of Aircraft.

1941 (Dec-Mar)

1941

1943

1944

1945
(up to Aug)

Grand Total

I

II

II

IV

Total

I

II

III

IV

Total

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Jan

Feb

Mar

Standard Planes

Flying Boat

24

87

3

9

5

6

7

8

7

8

11

9

9

10

92

9

8

8

5

3

3

3

4

6

4

2

2

57

3

263

17

21

26

28

25

11

13

8

Combat Plane Total

716

3665

454

483

474

494

541

723

641

716

802

786

718

849

7681

873

811

884

848

939

852

1006

1025

853

794

666

818

10369

24653

24896

1411

1758

2159

2353

2568

2639

2884

2278

Training Plane

30

308

74

95

98

94

106

114

142

165

191

212

223

281

1795

297

281

278

262

212

147

153

123

132

157

154

158

2354

378

4866

267

314

498

716

856

621

408

469

Training Seaplane

91

241

0

0

1

1

1

2

0

0

0

0

0

0

5

0

0

0

0

0

0

0

0

0

0

0

0

0

0

337

1

4

0

0

0

0

0

0

Training Plane Total

121

550

74

95

39

95

107

116

142

165

191

212

223

281

1800

297

281

278

262

212

147

153

123

132

157

154

158

2354

378

5203

268

318

498

716

856

621

408

469

TOTAL

837

4215

528

578

573

589

648

839

783

881

993

998

941

1130

9481

1170

1092

1162

1110

1151

999

1159

1148

985

951

820

976

12723

2843

30039

1679

2076

2657

3069

3424

3260

3292

2747

Special Planes

Oka, Type 11

0

0

10

50

95

93

160

197

150

755

0

755

10

238

507

Oka, Type 22

50

50

Shusui

0

1

1

4

5

1

Kikka

1

1

Total.

10

50

95

93

160

197

151

756

55

811

10

238

508

GRAND TOTAL

837

4215

528

578

573

589

648

839

783

881

993

998

941

1130

9481

1170

1092

1162

1110

1151

1009

1209

1243

1078

1111

1017

1127

13,479

2,898

30,910

1679

2076

2657

3069

3424

3270

3530

3253

--51--

APPENDIX I

15 March 1943

From: Chief of Naval Affairs Bureau, Navy Ministry

To: Chief of Military Preparations Bureau, Navy Ministry

Chief of Personnel Bureau, Navy Ministry

Chief of Education Bureau, Navy Ministry

Chief of Stores Bureau, Navy Ministry

Chief of Bureau of Supplies and Accounts, Navy Ministry

Chief of Medical Bureau, Navy Ministry

Chief of General Affairs Bureau, Naval Technical Department

Chief of General Affairs Bureau, Naval Aeronautical Department

Chief of General Affairs Bureau, Naval Civil Engineering Department

Subject: Inquiry on the Formulation of the Second Period Execution Plan for the Acceleration of War Preparations

As it has been decided that the predetermined armament program, the Revised Fifth Plan and the subsequent decisions on the request of the Navy General Staff will be handled collectively, according to the following acceleration policy, you are requested to submit your draft for the execution of such a plan by the end of March.

The First Period Execution Program of the war preparations acceleration policies mentioned in Navy Secretariat Document No 10490 of 1941, will be revised to include only the program to be executed by the end of March 1943.

The programs for the 1943 and fiscal years will be accelerated as the Second Period Execution Plan.

The Third Period Execution Plan is to be tentatively for the period from April 1945 to March 1948, but new definite plans, with the

--53--

previous plan as a reference, will be established to cope with the situation in the future.

The allocation of material is anticipated to be:

a. Steel

Name of Department and Bureau

Fiscal Year 1943

Naval Aeronautical Department

170,000 tons

Naval Technical Department

450,000 tons

Stores Bureau

111,000 tons

Naval Civil Engineering Department

170,000 tons

Military Preparations Bureau

15,000 tons

(Including allocations for each bureau)

2. Aluminum Allocation for Naval Aeronautical Department

65,000 tons (on the assumption that the allocation is equal to that of the Army).

The items to be noted by each department and bureau in drawing up the plan are as follows:

1. Naval Aeronautical Department

a. The execution plan will be formulated provisionally on the basis of amount of materials expected to be acquired readily. As for expansion and replenishment of the supplementary strength requested by the Navy General Staff Secret Document No 80, every possible measure will be taken hereafter for its fulfillment and, at the same time, further developments will be included in the above program with highest priority.

--54--

b. The training plan for flight personnel and the increase in personnel will be completed well before the equipment is prepared.

2. Navy Technical Department

a. The construction of the 42 escort destroyers (type D) requested by the Navy General Staff Secret Document No 37 will be accelerated to the utmost corresponding to the construction of anti-sub marine defense ships.

b. The production of arms and equipment for antiaircraft and defense operations will be increased by 30 percent as compared to the quantity decided by the policy of the Naval War Preparation Research Committee.

c. Engine manufacturing will be increased so that there will be sufficient engines for both new and damaged ships.

3. Stores Bureau

a. The construction of Kagoshima, Niitaka, and Sakhalin Fuel Depots may be delayed depending on the supply of materials, but a tentative plan will be established to secure as much aviation gasoline as possible.

b. Further economy of materials for each naval installation will be studied.

4. Naval Civil Engineering Department

a. The simplification of installations will be further investigated with a view toward economizing on materials and shortening the length of time required for the work.

--55--

b. Special importance will be attached to defense installations of air bases and operational areas and plans will be made so as to accelerate their construction.

c. The number of construction units to be organized in 1943 will be temporarily fixed at eight B units and one C unit. The number for 1944 will be decided later.

5. Personnel Bureau

In regard to the yearly reserves to be created, the organization of six special naval landing forces and six antiaircraft defense battalions was tentatively decided and their equipment will be provided accordingly.

6. Education Bureau

a. The training of 121,000 men in active service and 25,000 men in the first conscript reserve will be conducted in naval barracks or technical schools.

b. The training of men in the second conscript reserve and militia will be, as a rule, conducted by assigning them to units in the Homeland and overseas, except those to be assigned to special duties.

Note: Considerable changes to this plan may be necessary, depending on the supply of materials and change in the war situation. (Duplicate copy will be sent to: Chief of 2d Bureau, Navy General Staff)

--56--

Navy General Staff Top Secret Document No 142, dated 22 April 1943

From: Vice-Chief of Navy General Staff

To: Navy Vice-Minister

Subject: Proposal on wartime construction replenishment program and land defense strength reinforcement program for the fiscal year 1943.

Since the expansion of surface supply operations and reinforcement of submarines, antisubmarine vessels and land defense strength are considered absolutely necessary for the prosecution of the war, it is requested that these matters be given high priority in accordance with the following appended plan.

The details of the proposal will be discussed by the competent authorities.

Appended Plan

Wartime Ship Construction Replenishment Program and Land Defense Reinforcement Program for the Fiscal Year 1943

I. Ship Construction Replenishment Plan

The plan will be started in the fiscal year 1943 and generally completed by the end of the fiscal year 1945.

Ships to be constructed and principal items pertaining thereto are shown on Chart 1.

In carrying out this plan, the following points will be taken into consideration:

--57--

1. Cancellation of the projected construction of two B-class (new-type) cruisers.

2. Cancellation of the projected construction of three submarine tenders, and activation of the submarine base units.

3. Postponement or cancellation of the construction of four flying boat tenders.

4. Postponement or cancellation of the construction of some aircraft carriers.

II. Reinforcement of Land Defense Strength

A. Inner Combat Force

1. Antiaircraft Defense Strength

Antiaircraft defenses will be increased as rapidly as possible and generally completed by the end of the fiscal year 1945. The strength necessary for its maintenance and operation will be replenished thereafter. The selection of sites for fortification and other details will be discussed further (the increase in strength after the fiscal year 1943 in the previous deliberations will be included herein).

a. Antiaircraft Gun Batteries

Four hundred batteries, each equipped with six 12.7cm (or 12cm) antiaircraft guns and two searchlights. Approximately half will be mobile.

--58--

Chart No 1

Ships Planned to be Constructed under Navy General Staff Secret Document No 142

Type of Warship

Number of Ships

Standard Displacement
Tonnage

Speed

Cruising
Range

Other Items

High Speed Transport

32

Approximately 1,250 tons

Approximately 23 knots

18 knots

approx 3,500 nautical miles

1. 12cm or 12.7cm dual purpose guns

2

2. 25mm triple mounted machine guns

3 turrets

3. Depth charge

36

4. Echo ranging equipment

1

Hydrophone

1

5. Cargo capacity

about 200 tons

6. Landing barge

2

Cutter, Rubber float

quantity as required

7. Careful consideration will be given to facilitate the rapid loading and unloading of cargoes.

Transport Submarine

19

About 1,400 tons

Surface:

More than 12 knots

Underwater:

About 6 knots

Surface:

10 knots

6,000 nautical miles

Underwater:

3 knots

60 nautical miles

Besides these mentioned in the left columns and below, the characteristics of submarine (Class D) will be supplied to this transport.

1. Cannon equipment: One 25mm triple mounted machine gun on the bridge.

2. Torpedo equipment

None

3. Capacity of supply and transportation will be increased to a maximum.

4. Number of continuous cruising days

30 days

Motor Torpedo Boat (A)

100

About 80 tons

Type of No 10 Motor Torpedo Boat

Motor Torpedo Boat (B)

380

About 20 tons

Type of No 1 Motor Torpedo Boat

Escort

330

About 800 tons

About 16 knots

14 knots

about 5,000 nautical miles

1. Besides the items in the columns to the left, the escort vessels will be of the ship No 320 type, but the main armament consists of two main guns.

2. As the speed of merchant ships increases, some of the escort vessels will be of the ship No 320 type.

Auxiliary Patrol Boat (A)

90

About 200 tons

About 10 knots

About 8 knots,

About 4,000 nautical miles

1. Steel hull and substitutes to picket boats now assigned to the Fifth Fleet

2. For details refer to Inquiry of Naval General Staff, 2d bureau Secret Document No 115.

--59--

Chart No 1

Ships Planned to be Constructed under Navy General Staff Secret Document No 142 (Cont'd)

Type of Warship

Number of

Ships

Standard Displacement Tonnage

Speed

Cruising Range

Other Items

Auxiliary Patrol Boat (1)

300

About 200 tons

About 10 knots

8 knots

About 3,000 nautical miles

1. Generally the same as auxiliary patrol boat (A), but wooden hull.

2. Some will be of the No 1 auxiliary subchaser type.

Submarine (Medium)

50

(1) RO-35 and S-54 types will be adopted. After a study is made, a type of German submarine (without some of the weapons and fittings) may be adopted.

(2) Construction of Submarines A, B and C class and special type submarines will be cancelled after the fiscal year 1944 and submarines of this type will be constructed.

--61--

b. Machine Gun Batteries

Eighty batteries, each equipped with 24 25cm machine guns or larger.

c. Antiaircraft Defense (machine gun) Units

One hundred and twenty antiaircraft defense units, each equipped with 24 25cm machine guns or larger.

2. Surface Defense Strength

As a temporary measure, defense stations proposed by Navy General Staff Top Secret Document No 107 will be established as quickly as possible.

--63--

B. Outer Combat Force

Unit

Number of Units to be Newly Activated Each Fiscal Year

Remarks

1943

1944

1945

Antiaircraft
Defense Battalion

20

50

50

One battalion is composed of three antiaircraft gun companies (each with six guns), two machine gun companies (each with 24 guns) and one observation company (equipped with three radars and necessary equipment for lookout and communications)

Defense Unit

5

5

5

One unit is composed of two defense station units, one special minesweeper division and necessary defense base personnel

Special Naval Landing Force

Force to be maintained at a level whereby there would always be 5 reserve units

Includes No 1001 and No 1002 units (Paratroopers) and special submarine-borne landing forces (with amphibious tanks)

Communications Unit

2

2

1

Weather Unit

1

1

1

Survey Unit

1

1

1

Submarine Base Unit

1

1

1

Construction Unit

20

20

30

Each unit will have an organization adequate to construct defense facilities as well as air bases. The materials necessary for these units must first be provided and the personnel necessary for their operation each year will be ensured

Note: The details of organization and equipment of antiaircraft defense battalions and defense units will be discussed further.

--64--

APPENDIX III

3 June 1943

To: Vice-Chief, Navy General Staff

From: Vice-Minister of Navy

Subject: Reply concerning the wartime construction and replacement of naval vessels and the strengthening of the ground defenses in the 1943 fiscal year.

Regarding the establishment of the strength as proposed by the Navy General Staff Top Secret Document No 142, although the realization of the plan under the present circumstances is deemed extremely difficult, it should be possible to establish about half the requested strength if an urgent procurement demand for materials personnel and other items can be fulfilled. The work will start immediately according to the supplementary program as per the annex and every effort will be made to accelerate its execution.

However, due to the change in the allotment of materials, with the increase in production of aircraft and according to the production situation and collection of materials after 1944, a drastic revision of the program is highly probable.

As to your request for the establishment of strength other than the execution plan as per the annex, under the present circumstances this must be postponed until after 1946, although further study and consultations will be made.

--65--

ANNEX

Execution plan for wartime construction and replacement of naval vessels and strengthening of the ground defense strength in the 1943 fiscal year

1. Construction of Naval Vessels

a. Order of priority: escort vessels; motor torpedo boats and submarines; and patrol boats and transports.

b. Recommended Construction

Type of Ships

Fiscal Year

Total

Requested Strength

Remarks

1943

1944

1945

Escort

24

100

120

224

330

The speed is expected to be reduced to about 16 knots.

 

The shortage of Type A will be replenished by Type B

Motor  torpedo boat

A

0

8

20

28

100

B

150

240

62

452

Submarine (Medium)

0

0

13

13

50

Patrol boat

A

0

0

Undecided

Undecided

90

Studies will be made to construct A to the utmost in conjunction with the construction of miscellaneous auxiliaries.

B

About 60

120

120

300

300

High speed naval transport

0

4

6

10

32

D-type destroyers will be converted

Submarine transport

0

1

6

7

19

--66--

c. Postponement of construction of naval vessels according to preconceived plan.

The construction of the following naval vessels will be suspended, or the laying of the keel postponed, mainly for the purpose of diverting materials.

(1)

Four aircraft carriers

Ship No 5014 (keel laying scheduled for October 1944

Construction suspended

Ship No 5022 (same as above)

Ship No 5008 (Keel laying scheduled for September 1943)

Keel laying postponed about six months

Ship No 5009 (same as above)

(2)

Two B type cruisers

Ship No 5037 (Keel laying scheduled for August 1945)

Ship No 5038 (Since the keel laying is scheduled for August, 1946, the decision will be made later, following conferences)

(3)

Three submarine tenders

Ship No 5034 (Keel laying scheduled for December, 1945)

Ship No 5035

Since the keel laying is scheduled for after September, 1946, the decision will be made later.

Ship No 5036

(4)

Four flying boat tenders

Ship No 303 (Keel laying scheduled for October 1944)

Ship No 5031 (Keel laying scheduled for October, 1945)

--67--

Ship No 5032

Since the keel laying is scheduled for after July, 1946, it will be decided later.

Ship No 5033

(5) Oil tanker

Ship No 307 (Keel laying scheduled for August, 1944)

Ship No 5389 (Keel laying scheduled for August, 1944)

2. Ground Air Defense Strength a. Inner Combat Force

Chiefly from the viewpoint of air defense weapons, the realization of this plan is deemed difficult, but a plan will be made later in accordance with the measures to increase production of firearms.

b. Outer Combat Force

In view of the number of qualified personnel and amount of material available, for the time being, about half the requested quantities with respect to the AA defense units and construction units will be fulfilled. However, as soon as the goal for ordnance and personnel is fixed, reinforcements will be decided after further discussion.

--68--

Chart No 1

Required Operational Air Strength in Early 1945 Fiscal Year

Area Force

Carrier

Force

Ship-home Plane

Mobile Base Air Force

Training force

Inner Combat Force

Operational Total

Production Total

Remarks

Carrier fighter

381

72

453

900

A-fighter

864

1296

96

48

2304

3800

B-fighter

864

1296

96

324

2580

4250

C-fighter

432

648

48

72

1200

1700

Carrier bomber (carrier attack plane)

480

864

19

108

1996

3200

Lead bomber

480

864

48

36

1428

2100

Land attack plane

384

864

96

36

1380

1500

Land (carrier) reconnaissance plane

120

28

648

12

808

1000

About one-third of land reconnaissance planes of mobile base air force will be substituted by land bombers

Seaplane fighter

48

48

110

Reconnaissance seaplane

257

185

24

128

594

800

Patrol plane

288

160

448

500

Submarine attack plane

20

20

100

Submarine reconnaissance plane

36

36

50

Flying boat

64

8

72

90

Transport plane

90

825

14

104

1033

900

Total

4379

881

185

7305

626

1024

14400

21000

Remarks.

1. In addition to the above, about 9,000 planes must be produced for the training of flight personnel: therefore, besides the program for the training of 25,000 flight personnel for this fiscal year, every effort will be made to train an additional 10,000 men.

2. As soon as there are prospects for surplus materials and margin in production capacity, production will be increased.

--70--

Required Operational Air Strength in Early 1944

Area Force

Carrier force

Shipborne Plane

Mobile Base Air Force

Training force

Inner Combat Force

Operational Total

Production Total

Remarks

Carrier fighter

213

48

261

502

A-fighter

588

288

72

36

984

1902

To engage chiefly in destroying enemy fighter planes by means of dog fights.

B-fighter

516

288

72

108

984

1336

To engage chiefly in destroying enemy heavy bombers, with emphasis on speed and firepower.

C-fighter

120

72

24

36

252

352

To engage chiefly in night action using Type 2 land reconnaissance planes with fixed diagonal machine guns for the time being.

Carrier bomber

480

117

48

96

120

36

897

1478

Land bomber

96

24

120

170

Carrier attack plane

156

185

48

36

425

743

Lead attack plane

288

96

72

24

480

736

Land (carrier) reconnaissance plane

108

10

72

12

202

270

Type 100 headquarters reconnaissance planes.

Type 2 carrier reconnaissance planes.

Seaplane fighter

24

12

12

48

103

Reconnaissance plane

192

143

16

128

479

835

The majority of the planes other than shipborne are for antisubmarine patrol.

Patrol plane

(50) 74

(150) 270

(200) 344

(200) 390

Substituted carrier attack plane figures in parenthesis indicate intermediate trainer planes.

Submarine reconnaissance plane

22

22

44

Flying boat

48

8

56

72

Transport plane

50

135

9

101

295

205

Total

2644

525

213

1143

505

819

5849

9138

Remarks

1. In addition to the above, the production of about 2,500 planes is required for the training of flight personnel.

2. In addition to the flight personnel training program for 8,400 men, every effort will be made to increase this number as much as possible and the planes required there for will be secured.

3. In case prescribed number of carrier bombers and land reconnaissance planes is not attained, fighter planes will be substituted.

4. The number of planes shown in the "Production total" column is the number required to be produced in order to keep in the air. The number shown in the "operational total" column.

5. Ship-borne planes refers to those planes carried on such ships as battleships in contrast to the normal carrier force.

--71--

APPENDIX IV

Material for the Ninth Meeting of the Naval War Preparations Research Committee of Imperial General Headquarters

War Preparations Policy to Cope with the Third Phase Operations

The Army and Navy Ministries and General Staffs will make every effort to carry out the decisions of the Liaison Conference of the Imperial General Headquarters and Government of the formation of the 1944 National Mobilization Program and rush at top speed war preparations to cope with pressing war needs.

The principal aim of the war preparations is to establish an invincible war preparations plan by concentrating all efforts on completing the necessary plans during the fiscal years 1943 and 1944. At the same time, effective suicide attack tactics will be perfected.

In accordance with the above policies, the following measures will be taken:

1. Highest priority will be given to the establishment of land-based air strength as shown in Chart 1.

2. In principle, aviation fuel is to be secured to the limit of the resources and, for the present, the 1945 goal will be 1,800,000 kilolitres.

3. The construction and maintenance of naval vessels will be in accordance with the following policy:

--73--

a. As a rule, repairs to damaged ships will be given a higher priority than the construction of new ships.

b. The construction of ships will be performed as follows:

(1) Construction will be in accordance with the table prepared by the 1st Section, General Affairs Bureau, Navy Technical Department on 25 July 1943. The ships scheduled to be completed by the end of the 1944 fiscal year will be constructed according to the said table. As for destroyers (D-type), more than 10 ships, in addition to the above, will be completed by the end of the 1944 fiscal year by speeding up construction.

(2) The ships necessary for the organization of an amphibious group, mobility of the land based air force, transportation of the construction unit, continuous supply of the front line and for local defense will conform to Chart 2.

(3) As for construction of submarines, additions and changes are expected according to the results of research on mass production systems and new types of ships.

(4) The construction of ships according to the table prepared by the 1st Section, General Affairs Bureau, Navy Technical Department on 25 July 1943, other than the above, is given second priority from the viewpoint of general war preparations. The construction of ships Nos 5009 to 5015 and 5021 will be temporarily suspended. Also, preparatory works, except those deemed absolutely

--74--

necessary, will be discontinued before the final decision on these ships will be made by the end of the fiscal year 1943.

(5) Ship No 300 will be completed by the end of the fiscal year 1944 as an aircraft carrier.

4. The ground defense strength will be established in close conformity with Chart 3.

5. The preparations of personnel will be conducted speedily, before that of materials, in order to prevent disruption of operations of the various items mentioned in the preceding paragraphs. The first principle for the education and training of personnel is to enable them to cope with the present acute situation.

6. As for production of materials and use of the various installations, the policy of the eighth meeting of the War Preparation Research Committee will be followed. As well as economizing on materials through demonstration of the maximum efficiency of existing installations and utilization of idle installations, special efforts will be made to maintain and improve the fighting strength by increasing construction and repair capacities at the front and by establishing medical facilities on the spot.

7. The research on and realization of new weapons will be hastened to cope with the war situation. Radar and sonar equipment will be completed immediately, as previously arranged.

--75--

Chart No 2

Ships Necessary for Organization of an Amphibious Group

Type of Craft

Required
Number of
Vessels
to be
constructed
in Each
Fiscal Year

Remarks

1943

1944

Landing Craft

10

6

LCT

28

35

Special Large Landing Barge

40

60

Applicable to landing craft Type HA

Large Landing Barge

Steel

1,400

2,400

Required number of vessels in 1945 generally corresponds to that of 1944

Wooden

700

1,200

Medium and Small Landing Barge

140

240

Armored Boat

70

60

PT Boat

600

960

High Speed Transports

15

15

10 vessels for the tentative program, and additional construction of 20 vessels

--76--

Chart No 2

(Continued)

Reference Table

(Main Data of Transport and Amphibious vessels)

Type of Craft

Standard Displacement Tonnage

Speed Knots

Cruising Range (nautical mi.)

Carrying Capacity

Remarks

Landing Craft

About 800 tons

13

2,000 mi. at 13 knots

300 tons (4 med tanks)

Capable of beaching

LCT

About 950 tons

16

3,000 mi. at 16 knots

350 tons (13 med tanks)

"

Special Large Landing Barge

About 16 tons

350 mi.

15 tons (1 med tank)

"

Large Landing Barge

About 10 tons

8

300 mi.

10 tons

"

Medium Landing Barge

8 tons

8

250 mi.

10 tons

"

Small Landing Barge

5 tons

7.5

200 mi.

3 tons

"

High Speed Armored Boat

22 tons

35

140 mi.

Zero

With two 20mm machine guns

PT Boat

22 tons

17-25

300 mi.

2 tons (with Special equipment)

High Speed Transport

1,500 tons

21.5

3,500 mi. at 18 knots

350 tons

Capable of rapid loading and unloading with two 12cm antiaircraft guns, nine 25mm machine guns

--77--

Chart No 3

Increase of Ground Defense Strength

1. Inner Combat Force

a. Antiaircraft Strength

The following strength will be attained by the end of the 1945 fiscal year and thereafter the necessary strength to maintain and operate it will be provided.

(1) Antiaircraft Gun Batteries

400 batteries

One battery will be provided with six 12.7cm (or 12cm) dual purpose guns and two searchlights as its nucleus. About one-half of the battery will be mobile.

(2) Machine Gun Batteries

Eighty batteries with 24 large (25-mm and over) machine guns as its nucleus.

(3) Antiaircraft (machine gun) Defense Unit

120 antiaircraft defense units with 24 large (25-mm and over) machine guns as its nucleus.

(a) Surface Defense Force

The preparations of defense stations in accordance with Navy General Staff Top Secret Document No 107 will be expedited to the utmost for the present.

--78--

Chart No 3

2. Outer Combat Force

Unit

Annual Requested Increase in Strength in Each Fiscal Year

Remarks

1943

1944

1945

Antiaircraft Defense Unit

A

60

150

150

Unit A is composed of six dual purpose guns. Unit B is composed of twenty-four 25mm machine guns

B

40

100

100

Garrison Unit (Defense Unit)

10

5

5

Composed of about two companies of a land combat unit, about 100 men of the sea defense unit, 20 large landing barges, three A underwater defense stations, two B underwater defense stations and base clerical staff

Special Naval Landing Force

Four reserve forces to be maintained at all times

Includes Nos 1001 and 1002 units and special submarine landing forces attached thereto

Communications Unit

2

2

1

Weather Unit

1

1

1

Survey Unit

1

1

1

Submarine Base Unit

1

1

1

Surface Transport Unit

4

6

6

Forty large landing barges and four armored boats as the nucleus.

Construction Unit

50

100

100

Necessary materials according to the number of units will be provided and the necessary members for the operating of the construction units will be secured

Coastal Battery

80

60

40

Figures indicate the necessary number of 8cm - 20cm guns. Gun barrels on hand and removed from vessels will as a rule, be appropriated. (Necessary gun-carriages will be hastily constructed)

Type 2 (3) Special Amphibious Tank

240

480

480

The figure shows the number of tanks. Necessary personnel will be assigned

--79--

Japanese Monograph No. 174

OUTLINE OF NAVAL ARMAMENT PREPARATIONS FOR WAR

PART VI

DRAFT

PREPARED BY

MILITARY HISTORY SECTION

HEADQUARTERS, ARMY FORCES FAR EAST

DISTRIBUTED BY

OFFICE OF THE CHIEF OF MILITARY HISTORY

DEPARTMENT OF THE ARMY

HEADQUARTERS

FAR EAST COMMAND

MILITARY HISTORY SECTION, SPECIAL STAFF

JAPANESE RESEARCH DIVISION

Outline of Naval Armament and Preparations for War, Part VI

JAPANESE MONOGRAPH No 174

Through Instructions No. 126 to the Japanese Government, 12 October 1945, subjects Institution for War Records Investigation, steps were initiated to exploit military historical records and official reports of the Japanese War Ministry and Japanese General Staff. Upon dissolution of the War Ministry and the Japanese General Staff, and the transfer of their former functions to the Demobilisation Bureau, research and compilation continued and developed into a series of historical monographs.

The paucity of original orders, plans and unit journals, which are normally essential in the preparation of this type of record, most of which were lost or destroyed during field operations or bombing raids rendered the task of compilation most difficult; particularly distressing has been the complete lack of official strength reports, normal in AG or G3 records. However, while many of the important orders, plans and estimates have been reconstructed from memory and therefore are not textually identical with the originals, they are believed to be generally accurate and reliable.

Under the supervision of the Demobilisation Bureau, the basic material contained in this monograph was compiled and written in Japanese by former officers, on duty in command and staff units within major units during the period of operations. Translation was effected through the facilities of Military Intelligence Service Group, 02, Headquarters, Far East Command.

This Japanese Operational Monograph was rewritten in English by the Japanese Research Division, Military History Section, Headquarters, Army Forces Far East and is based on the translation of the Japanese original Editorial corrections were limited to those necessary for coherence and accuracy.

FOREWORD

This is the last of a series of six monographs in regard to Japan naval armament in preparation for and during the Pacific War.

Additional monographs covering Japan's naval armament plans are.

Mono No

Outline of Naval Armament and Preparations for War, Part I

145

Outline of Naval Armament and Preparations for War, Part II

149

Outline of Naval Armament and Preparations for War, Part III

160

Outline of Naval Armament and Preparations for War, Part IV

169

Outline of Naval Armament and Preparations for War, Part V

172

24 November 1952

TABLE OF CONTENTS

Page

Contraction and Consolidation of Strategic Areas to be Defended at All Costs

1

General Situation

1

Increase in War Production

2

Withdrawals to Shorten the Line of Defense and Concentration of Defensive Power on Inner Lines

7

Preparations Based on Ail-Out Special Attack Tactics

8

Details of Preparations for Special Attack Operations of the Naval Air Forces

12

CHARTS

Chart No 1

Increase and Decrease in Bottoms During the Pacific War

3

Chart No 2

Status of Aircraft for the "Ketsu-Go" Operation

12

Chart No 3

Outline of the Special Attack Production Plan

16

Chart No 4

Construction Schedule of Special Planes, 20 June 1945

16

Chart No 5

Actual Results and Estimate of Production of Special Planes, 15 July 1945

16

Chart No 6

Secret Bases

18

Chart No 7

Status of Bases for Model 43 Oka

18

Chart No 8

Condensed Report of the Results of Tests at Takeyama Base

21

Chart No 9

Results of "Ko-Go" Tests at Kure Navy Yard

21

Chart No 10

Results of Surface and Underwater Special Attack Weapons Preparation

22

--i--

Page

Chart No 11

Table of Organization of Special Attack Squadrons

22

Chart No 12

Location of Special Attack Bases, 15 August 1945

22

APPENDICES

Appendix I

Major Naval Arms and Weapons Produced from January 1944 to Cessation of Hostilities

Appendix II

Agreement between the Army and the Navy Concerning War Preparations for the First Half of Fiscal Year 1945

Appendix III

Naval General Staff Secret Document No 31

--ii--

Contraction and Consolidation of Strategic Areas to be Defended at all Costs

General Situation

At the time the War Preparations Plan, Phase Three, was being deliberated, the situation in the Solomons-New Guinea area was rapidly deteriorating. The tremendous amount of equipment able to be produced by the United States as compared with that produced by Japan was having its effect. Taking into consideration her national resources and scientific technical capacity, Japan recognized that it would be impossible to hold her own-on her greatly extended fronts. It was, therefore, decided at a council meeting held in the presence of the Emperor on 30 September 1943, to contract and consolidate the strategic areas at all costs.

The main points decided by the Council, in the presence of the Emperor, were that, by the middle of 1944, strategic preparations would be completed to cope with the Anglo-American offensive; the areas to be held at all costs in the Pacific and Indian Oceans were the Kurile Islands, the Bonin, Mariana and Caroline Islands, western New Guinea, Sunda and Burma, and every effort was to be made to maintain sea communications with these areas.

In accordance with the above, transportation of war supplies to areas outside the areas specified at the conference, which had been conducted up to that time despite heavy losses of warships, transports, aircraft, munitions and men, was to be reduced to a minimum and the main ef-

--1--

fort was to be directed toward the strengthening of defense in the strategic areas to be defended at all costs.

This decision was made too late, however, and even the new line of defense was too extensive for Japan's national resources and military capabilities. The burden of immediate war preparations, therefore, was not eased, and, at the same time, the difficulties in transportation of war supplies mounted daily, caused by the increasing activities of enemy submarines and aircraft. This greatly delayed the bolstering of defenses in the various areas.

Increase in War Production

As stated in Monograph 172, the Navy had embarked upon the Revised Fifth Naval Armament Expansion Program. This called for the nation, as a whole, to muster its entire power in order to attain the production goal set forth by the "Joint Army-Navy Study in regard to the Material Mobilisation Plan for 1943." During the second half of 1943 and the first half of 1944, although production failed to reach the goal set forth in the Revised Fifth Plan, great advances were made, and production reached a peak unprecedented in Japan's history. Had the American invasion of the Marianas, Carolines and Philippines been delayed approximately six months, the implements of war produced by this greatly stepped-up productive effort would have had a marked effect on the war effort.

It is interesting to note that the upward trend in production, which was not affected by the loss of Saipan or Palau, took a sharp downward

--2--

plunge after the line of communications to the Southern Areas was severed following the Battle of Leyte and also after Japan proper was exposed to air raids.

The major arms and weapons required for naval operations which were produced from January 1944 to the end of the war are shown in Appendix I.

Although construction of merchant ships was also greatly accelerated by the drastic measures adopted by the Japanese Navy, ship losses, as a result of enemy action, greatly exceeded the construction tonnage, sharply reducing available merchant ships. This was felt to be one of the main reasons for Japan's defeat in the Pacific War.

Chart 1 shows the increase and decrease in bottoms during the Pacific War.

The intensification of war preparations at the front, which was conducted on the basis of the conference in the Imperial Presence on 30 September, was primarily aimed at training and replenishing the fleet and strengthening defensive power in key areas. However, the fleet training did not progress satisfactorily because the greater part of our air strength had to be diverted to the Solomons and New Guinea areas to fight battles of attrition aimed at slowing the enemy's advance. In early February 1944, the Marshall Islands were occupied by the enemy. This meant that our key areas were directly threatened by the enemy. On 17 February, Truk Island, the anchorage of the main force of our fleet, was subjected to a formidable air raid by an enemy task force. This forced the greater part of our surface units to retreat toward Palau,

--3--

Chart No 1

Increase and Decrease in Bottoms During the Pacific War

(Quantities in thousands of gross tons)

Period

Increase
by
Construction

Decrease
by Losses

Decrease

Total

Percentage
Available

At the outbreak of the war

6,384.0

100

December 1941

44.2

51.6

7.4

6,376,6

99

December 1942

661.8

1,095.8

434.0

5,942.6

93

December 1943

1,067.1

2,065.7

998.6

4,944.0

77

December 1944

1,735.1

4,115.1

2,380.0

2,564.0

40

1945 (up to august)

465.0

1,562.1

1,097.1

1,466.9

23

At the end of the war

1,466.9

23

Remarks: The above table shows statistics on steel ships of over 100 tons.

--4--

Davao and Lingga areas. Under these circumstances, it was practically impossible to continue fleet training. Moreover, the activities of enemy aircraft and submarines made our sea communications more and more difficult and transportation of personnel, weapons and other supplies to the Fleet were seriously hampered.

The following is an outline of the measures taken for strengthening defenses in the key areas up to the time of the Leyte Operation, including the Battle of Saipan. This covers approximately one year, to the latter part of October 1944.

Air Defense Units: It was decided to activate 103 air defense units and to dispose them at strategic points on the periphery of the key area, and also at such locations inside the area as Formosa, Ryukyu and Bonin Islands. Upon arrival at their destination, such units were to become an organic part of local base forces or guard units.

The original plan called for Type A air defense units, to be equipped with six antiaircraft guns (12.7cm) and two searchlights, and Type B units, to be equipped with 24 25mm machine guns as their basic equipment. The shortage of antiaircraft guns, however, mads activation of Type A units practically impossible. Hence, most of the units that ware sent to the front were Type B and naturally their defensive power was not great. However, losses at sea were only three of the 103 units. Insofar as the number of units was concerned, the scheduled disposition was generally successful. It was also planned to reinforce the front with more antiaircraft guns and mounts as soon as such equipment became avail-

--4--

able. This plan, however, never materialized because of the drastic changes in the war situation.

Construction Units: Arrangements were made to activate 25 construction units and to dispatch them, according to the following schedule, to expedite completion of airfields and the strengthening of the defense setup in the areas concerned:

South Seas Area (Truk, Saipan, Guam and Palau):

10 construction units

(Two of these units were later reorganized and diverted to other areas following the sinking of their transports)

Western New Guinea Area:

4 units

Ambon, Kai and Aroe Islands:

5 units

Philippines:

3 units

Andaman Islands:

3 units

Each unit was composed of from 700 to 1,000 personnel and was equipped with the necessary construction material, transportation equipment and light weapons. It was no easy matter to send these units forward, not only because of the large amount of transportation required but also because of the debarkation facilities necessary when they arrived at their destination.

As only very few special land combat units (guard units) were activated during this period, it was necessary to station Army troops on even small isolated islands, in accordance with the fundamental concept that the Army would constitute the main force in land combat. At the same time, steps were taken to coordinate the command system of the Army

--5--

and the Navy. Naval units were provided with as many land combat weapons as possible regardless of their assigned areas in order to strengthen the over-all defensive power.

Other major steps taken at this time were: activation and disposition of transport units to increase local transport capacities; strengthening of such organs as the construction and repair departments and air depots to raise construction and repair efficiency in each sector; dispatching of torpedo-adjustment squads as part of the measure to increase the efficiency of supply and maintenance; assignment of tactical guidance squads and technical guidance squads for the improvement of fighting power and techniques; installation of radar equipment at the front, and establishment of personnel recruitment sections in all area fleet headquarters, to which several hundred reserves were assigned.

Despite these efforts, the rapid decline of Japan's national power and industrial potential could not be halted. The main reasons for this were that the implementation of the decisions cams too late; the else of the defensive sphere was too great for Japan's national and war potential; United States forces were driving westward with overwhelming strength through the Mariana and New Guinea areas, making lightening advances, and Japan's surface supply lines were under increasing pressure. This was especially true after the middle of 1943, when communications between the Southern Region and Japan proper were seriously menaced through lack of air supremacy in the Mariana, Caroline and Philippine areas.

--6--

Efforts to strengthen Japan's defensive power merely resulted in a situation where in an effort to defend all points, none were strong. This was attributed to failure to appraise the situation correctly and to adopt a thorough priority system for the areas to be defended.

Withdrawals to Shorten the Line of Defense and Concentration of Defensive Power on Inner Lines

In February 1944, just as several defensive projects, based on the national policy as agreed at the Conference in September 1943, were being put into effect, United States forces, which had already occupied the Marshalls area, launched an all-out air attack against Truk. Next, during the latter part of March and early April, they launched large scale air attacks against the Palau area. Simultaneously, they occupied the northern coast of New Guinea and continued their advance. In the latter part of May they succeeded in seizing Biak Island. Subsequently, on 9 June, they launched operations to occupy Saipan.

The Navy, based on its estimate that the battle for the Marianas would constitute the decisive battle of the war between Japan and the Allies, carried out "A-GO" Operations, throwing almost the entire fleet into the fray. Despite desperate fighting, the battle situation became worse and the Japanese forces retreated after their air and surface forces had sustained critical losses. It was felt that prospects of victory were fast fading with the defeat of the forces in the Marianas area.

The tempo of advance of the United States forces increased steadily. They occupied Tinian Island in July and Peleliu and Morotai Islands by

the middle of September. In October, enemy task forces conducted air

--7--

raids on Formosa and the Ryukyus. On 20 October, the enemy launched a campaign to occupy the Leyte Gulf area. At this juncture, our fleet, although not fully recovered from the damage sustained in the "A-GO" Operations, and consequently unprepared for a decisive battle, launched a desperate assault upon the enemy with its entire forces. Because of the enemy's air supremacy, however, our fleet was dealt a near fatal blow in this engagement. This resulted in air and sea supremacy, which the Japanese forces had maintained for years in the Far East, being completely yielded to the enemy.

The Japanese Navy, under the circumstances, was confronted with the necessity of drastically shortening its defense lines. It was decided to limit the key area to the area extending from the Kuriles to Formosa, and, at the same time, to establish impregnable defenses on Japanese islands south of the Homeland as well as on Iwo Jima and the Ryukyus. The greatest defensive strength was to be concentrated on Iwo Jima and Okinawa. These emergency changes in policy were carried out within the required time limit because of the proximity of the involved areas to the Homeland, and, at the same time, steady progress was made in the fortification of the inner sectors.

Preparations Based on All-Out Special Attack Tactics The concept of special attack tactics (the tactic of resorting to one-way or suicidal missions for certain destruction of the target) was not entirely new in the history of the Japanese Army and Navy. The Port Arthur blockade in the Russo-Japanese War, the demolition mission of the

--8--

three demolition tube heroes (Nikudan-Sanyushi) in the Chine Incident and the midget submarines employed at Pearl Harbor, all possessed some features of special attack tactics. There are also many instances in the history of Japan in which men voluntarily acted in a manner similar to a special attack mission, but these acts were not specifically ordered by their superiors. The attacks carried out by the Kamikaze Special Attack Unit and the Type A Midget Submarine Unit (Cebu) during the operations in the Philippines area, during and after October 19143, were probably the first attack missions that were planned and ordered by competent commanders. The results achieved by these special attack units were unexpectedly good in comparison to the small force committed. However, it was felt that it was a great tragedy that Japanese field commanders were forced to resort to such tactics because of the rapidly deteriorating situation resulting from the enormous difference in fighting power between the Japanese and Allied forces.

These desperate attack tactics employed by field forces were inevitably reflected in the policies adopted by those concerned with war preparations. Urgent demands for the production of weapons suitable for these special attack tactics originated in the Naval General Staff and immediate response was given to the commands by the Navy Ministry. Inasmuch as the Japanese Navy had been studying weapons for this type of warfare for some time, naval authorities were fairly optimistic regarding the realisation of the project. The greatest difficulty was that the immediate need for such weapons allowed little time for trial manu-

--9--

facture, tests and research.

In October 1943, as a result of negotiations between the Navy Ministry and the Naval General Staff, the following agreement was reached:

The Oka type aircraft (Maru Dai), which had already been tested and approved for special attack purposes, would be used. The Kaiten (commonly known as human torpedoes) and the Shinyo (commonly known as crash boats), in addition to the Type A midget submarine which had already been produced, would be used for surface attacks. Trial manufacture and test runs were made where necessary, and activation of training units was begun.

By adopting latent plans, a variety of new weapons for special attack tactics was produced by the end of 1944. Mass production of such weapons as aircraft known as the "Shusui" and "Kikka", and surface and underwater weapons known as the "Koryu" and "Kairyu" were planned and initiated. In addition, numerous other latent designs were adopted and produced.

In February 1945, the outcome of the Philippines campaign had been decided and, by the end of the same month, the supposedly impregnable fortress of Iwo Jima had been lost after furious fighting. It became increasingly clear that the enemy was about to launch large scale air raids against the Japanese Homeland. Under the circumstances, as were forced to concentrate our war preparations on the production of aircraft and special attack weapons and the completion of defenses for the decisive battle for the Homeland. In view of this situation, the Japanese

--10--

Navy dispersed its production facilities while maintaining a maximum output, strengthened air defenses and, at the same time, initiated all-out war preparations based on special attack tactics.

All war preparations were executed in close cooperation with the Army and each service augmented the deficiencies of the other. This was clearly indicated in the agreement reached between the Army and Navy High Commands on 1 April 1945 (Appendix II).

In accordance with this agreement, on 6 April 1945, the Naval General Staff held a conference with the Navy Ministry in order to decide on the war preparations to be made during the first half of the fiscal year 1945. Details of this conference are given in Naval General Staff Secret Document No 31, 6 April 1945 (Appendix III).

The Navy Ministry completed all research work and reached full agreement with the War Ministry. Although some slight differences in estimates had to be adjusted, the Navy Ministry mapped out a plan of execution which was generally in line with the Naval General Staff's demand and devoted itself to its enforcement.

In the meantime not only did Iwo Jima fall in late February and the Okinawa Invasion Operation begin in early April, but the Homeland was also subjected to large scale day and night air attacks, which occurred almost continuously after the beginning of March. This resulted in heavy damage to personnel and equipment and gravely threatened communications with China and Korea. As a result, the nation's resources, war potential and productivity began to show a rapid decline.

--11--

Detailed plans were made to ready a total of 5,000 standard aircraft, including those newly built or repaired, to equip most of them with special attack equipment and, at the same time, to accelerate as much as possible mass production of special attack aircraft. As far as standard aircraft was concerned, we fell only slightly short of our goal. However, production of special type aircraft lagged considerably, especially the "Shusui", "Ki 115" and "Kikka" types. Although these latter were begun, they were not completed in time to contribute to the war effort.

The status of aircraft for the "Ketsu-Go" Operation, (Homeland Decisive Battle) as of 15 July 1945, was as shown on Chart 2.

Details of Preparations for Special Attack Operations of the Naval Air Forces

First Phase: Since operations on the Japanese mainland itself were considered inevitable as the next phase of operations at the time of the commencement of the Iwo Jima Operation in February 1945, a plan was formulated on 1 March to reorganize the entire naval air forces, primarily for the purpose of launching special attacks. On the same day, the Naval Combined Air Training Command was reorganized into the Tenth Air Fleet and incorporated into the Combined Fleet. Because of the acute shortage of aircraft, as well as fuel, at that time, priority was given to the training of special attack units and training of flight personnel, in general, had to be temporarily suspended. With preliminary training and preparations for converting training aircraft into special attack planes gener-

--12--

Chart 2

Status of aircraft for the "Ketsu-Go" Operation

No. of Aircraft

3d Air Fleet

5th air Fleet

10th air Fleet

Total

Type of Aircraft

Allot

Opnl

Allot

Opnl

Allot

Opnl

Allot

Opnl

"Ko"-type Fighters

312

200

242

141

119

75

673

416

"Otsu"-type Fighters (Interceptor)

137

50

136

55

3

2

276

107

"Hei"-type Fighters (Night fighter)

133

91

28

16

161

107

Bombers

88

60

166

111

254

171

Carrier-bombers

157

113

119

99

99

65

375

277

Carrier-based Attack Planes

90

80

52

44

65

24

207

148

Land-based Bombers

40

32

49

40

89

72

Land-based Attack Planes

25

12

60

48

112

63

197

123

Land-based Recon Planes

49

31

55

16

104

47

Seaplanes

152

120

71

69

223

189

Intermediate Trainer

478

275

1,106

978

659

445

2,243

1,698

"Shiragiku" Utility Trainer

167

131

238

174

19

15

424

320

Total

1,740

1,135

2,244

1,740

1,242

800

5,226

3,675

Abbreviations: Allot — Allotment Opnl — Operational

ally reaching completion in the middle of May, the 11th Air Flotilla, whose strength was approximately half that of the Tenth Air Fleet, and one-half of the 13th Air Flotilla resumed training.

The bombs to be loaded on the training aircraft which had been converted into special attack planes were as follows:

Type of Aircraft

Bombs (kg)

Number

Type-93 Intermediate Trainer

250

1

Type 2 Intermediate Trainer

250

1

SHIRAGIKU Utility Trainer

250

2

Type-94 Reconnaissance Seaplanes

250

2

Type-95 Reconnaissance Seaplane

250

1

Type Zero Reconnaissance Seaplane

250

2

Type Zero Observation Plane

250

1

Type Zero Training Fighter

250

1

Type Zero Carrier Fighter

250
or
500

1

1

Second Phase: The enemy landed on Okinawa in late March 1945 and as hostile attacks against the Japanese mainland became imminent with the unfavorable conclusion of operations in this area in late June, a speedy completion of preparations for the decisive battle on the mainland became imperative. It was estimated at that time that the enemy invasion of the mainland, anticipated about September at the earliest, would be directed against the southwestern part of Japan proper and that the first wave of the enemy invasion forces would comprise approximately 10 divisions carried by 1,000 transports. It was also estimated that if army and naval

--13--

air forces could succeed in sinking half of the transports within the first ten days of the landing, the enemy's attempt could be smashed. On the basis of the above estimate, the Navy undertook to construct approximately 5,000 standard aircraft by the middle of August.

Furthermore, with a view to compensating for losses and preparing for the second and succeeding assaults of the enemy, the need for special aircraft, taking into consideration such factors as aircraft, fuel and flight personnel, became absolutely imperative. The number of standard aircraft to be built was estimated at 5,000 on the basis of the following figures.

Number of enemy vessels to be sunk:

500

Estimated ratio of hits by suicide planes (based on battle experience gained at Okinawa)

Against the carrier striking forces

1/9

Against troops transports:

1/6

Number of aircraft required against troop transports:

3,000

In addition to the above, taking into consideration the condition of our aircraft at that time, approximately 350 planes were to be assigned to attacks against the carrier striking force and, taking their actual operating capacity and losses prior to the operation into consideration, the number of aircraft required was estimated at 5,000.

In carrying out the decisive battle on the mainland, the naval air forces planned to thwart the maneuverings of the enemy's carrier striking force with one element and attack the troop transport with their main

--14--

Matters to which special attention was given for the maximum utilization of the entire naval air strength, as mentioned above, were as follows: speedy preparation of standard aircraft; speedy preparation of special aircraft; construction and strengthening of air bases, and measures for increasing the efficiency of the special attack planes.

a. Speedy preparation of standard aircraft:

(1) Measures taken to secure aircraft productions The growing intensity of enemy air attacks, as well as the confused state of production and transportation, seriously hampered production of new aircraft. Especially, because of heavy damage to engine plants, production of engines did not keep pace with production of fuselages. Therefore, every effort was made to secure the production of new aircraft by equipping newly-built fuselages with repaired engines.

(2) Acceleration of aircraft repairs: Among the aircraft requiring repairs at that time, the work on approximately 700 planes was expected to be completed by the middle of August. To facilitate maintenance of these aircraft, repair teams, organized by mobilising all technicians of the Air Technician Depot, the Yokosuka Naval Air Group and the research organs of each construction and repair unit, were dispatched to the bases.

(3) Equipping standard aircraft with special attack weapons: All aircraft, except training seaplanes, were equipped with special attack weapons.

--15--

b. Speedy preparations of special aircraft: To supplement the shortage of standard aircraft, construction of special aircraft was required. From the viewpoint of battle preparations, these special attack aircraft, which had originally been designed for special attack purposes, had many advantages compared with the standard aircraft.

Because of the decrease in production and repair capacities due to enemy sir raids and the lack of training for flight personnel, and because of the shortage of aviation fuel, standard aircraft could not meet even half the operations requirements either in quality or quantity. Therefore, special aircraft were required to satisfy the following general conditions: A high ratio of hits (by the adoption of special attack methods): maximum effectiveness: economy of materials; simplicity of operation; simplified training (so that the planes could be operated by young flight personnel); economy of fuel, and high performance.

The plans for the production of special planes and the actual results achieved are shown on Charts 3, 4 and 5.

c. Maintenance and strengthening of air bases: Since the interceptor fighters and the antiaircraft defense capabilities on the ground were inadequate and as aviation fuel was running low, also there was a great strength disparity between friendly and hostile air forces, restrictions on the aggressive use of interceptor fighters were inevitable. Therefore, the adoption of an effective plan for ground defense against heavy air attacks and for the preservation of the necessary air strength until the decisive battle on the Homeland was imperative.

--16--

Chart 3-a

Outline of the Special Attack Production Plan

Kikka

Objective

1

Acquisition of land attack planes suitable for attacks on enemy ships approaching within a short distance. To be mass production.

Type

2

Turbine-rocket twin-engined monoplane

Principal Measurement (Meters)

3

Smallest possible type. Measurement when wings are folded:

Full width: 5.3

Full length: 9.5

Full height: 3.1

Engines to be Installed

4

Two TR-12 Engines

Crew

5

One

Capacity and Armament

Maximum
Speed
(Knots)

6

335 Close to sea level.

365 At an altitude of 6,000 meters

Range

7

200 miles close to sea level

300 miles at an altitude of 6,000 meters

Climbing Power

8

Landing
Speed
(Knots)

9

80

Bomb Load (kg)

10

500

Radio Equipment

11

Model 3, Type-1 Radio-telephone set

Receiver only

Air Groups in Charge (Date of Activation)

12

724th Air Group (1 July 1945)

Remarks

13

Undergoing experimental production and tests. About six months behind the scheduled date of completion and still incomplete.

Chart 3-b

Outline of the Special Attack Production Plan

Oka

Type 11

Type 22

1

Acquisition of special attack gliders that may be released from the Type-1 land attack plane

Acquisition of special attack planes which may be released from "Ginga" and which are capable of .flying by their own power

2

Powder-rocket midwing monoplane

Rocket-engined midwing monoplane

3

Full width: 5.6

Full length: 6.06

Full height: 1.16

Full width: 4.12

Full length: 6.88

Full height: 1.15

4

Three powder rockets

One Tsu-11 Engine

5

One

6

7

20,000 meters when released at a speed of 250 knots at an altitude of 3,500 meters

50 miles when released at sea level.

70 miles when released at a speed of 240 knots at an altitude of 4,000 meters

8

9

10

1,200

600

11

12

721st Air Group (1 Oct 1944)

722d Air Group (15 Feb 1945)

13

Used in the Okinawa operation and proved to have excellent performance

Experimental production was completed. Although good results were obtained there was no opportunity to use the plane in battle

Chart 3-c

Outline of the Special Attack Production Plan

Oka

Shusui

Type 43

1

Acquisition of special attack planes which may be released from the "Renzan" or catapulted from the ground

Acquisition of rocket-engined interceptor fighters with a great capacity

2

Turbine-rocket midwing monoplane

Rocket-engined tailless monoplane

3

Full width: 9.0

Full length: 8.16

Full height: 1.15

Full width: 9.5

Full length: 5.85

Full height: 2.7

4

One NE-20 Engine

One KR-10 Engine

5

One

6

10,000 meters

7

5.5 minutes after climbing to an altitude of 10,000 m at a maximum speed of 432 knots

8

Takes 3.5 minutes to climb to an altitude of 10,000 meters

9

10

800

11 30mm machine guns

11

Receiver only

Receiver only

12

725th Air Group (1 Jul 1945)

312th Air Group (5 Feb 1945)

13

Now undergoing experimental production and tests. For coastal defense purposes, this type of plane which may be catapulted from the ground, is under production in great numbers.

Test flights were undertaken twice, but failed owing to defective engines, and the crew perished. Experimental production carried out jointly by the Army and Navy.

Chart 3-d

Outline of the Special Attack Production Plan

Toka

KI-115

Baika

1

"KI-115" plane with "HA-33" engine

Acquisition of special attack planes in which various types of engines such as the "Kotobuki", "Sakae", "Kinsei" and "Zuisei" nay be installed

Acquisition of special attack gliders designed to attack small landing craft approaching within a short distance

2

Single-engined low-wing monoplane

Single-engined low-wing monoplane

Rocket-engined low-wing monoplane

3

Full width: 6.72

Full length: 8.50

Full height: 3.10

4

One HA-33 Engine

Rocket engine built fa experimental purposes

5

One

One

One

6

280 . . . At an altitude of 4,200 m

250

7

Approximately 600 miles

150 miles

8

9

10

500

500

250

11

Receiver only

Receiver only

12

13

Row undergoing experimental production and tests. Converted Army planes

Now undergoing experimental production and tests. Same type as the Army plane built for experimental purposes.

War ended while the demand for experimental production was under discussion

Chart 4

Construction Schedule of Special Planes

(20 June 1945, First Section, General affairs Bureau, Aeronautical Department)

May

Jun

Jul

Aug

Sept

Oct

Nov

Dec

Oka (Model 22)

6

49

30

50

60

60

60

Oka (Model 43)

2

10

22

38

65

80

Kikka (By Aeronautical Department)

Experimental

12

Manufacture

13

125

Final

11

Kikka

(By Naval Technical Department)

10

40

Shusui

35

90

145

225

Ki 115

10

150

320

400

Chart 5

Actual Results and Estimate of Production of Special Planes

(15 July 1945, Second Section, General Affairs Bureau, Aeronautical Department)

Type

Name of Manufacturer

Apr

May

Jun

Jul

Aug

Sept

Shusui

Mitsubishi Co

4

5

14

35

Japan Aircraft Co

1

7

22

50

Fuji Co

1

3

Kikka

First Depot

1

10

30

45

First Air Depot

(2 Tng)

5 - (3 Tng)

Kyushu Aircraft Co

5

15

Naval Technical Depot

Oka

(Model 22)

First Technical Depot

Aichi Co

5

20

40

Oka

(Model A3)

First Technical Depot

8

12

12th Air Depot

Aichi Co

Ki 115

Naval Technical Dept

40

Showa Co

10

Abbreviation: Tng — Training Plane

On the other hand, in order to effect maximum utilization of the counterattacking capabilities of our aircraft within the shortest possible time (in approximately 10 days) against an enemy invasion of the Homeland, training planes of poor maneuverability and special planes had to be assigned in advance to areas near the anticipated invasion point. Since special installations were necessary for these special planes, because of their characteristics, the bases then in use were inadequate. Accordingly, maintenance of the bases was carried out in the following phases.

Strengthening of established bases: To strengthen the 70 established land plane bases and the 24, seaplane bases in the Homeland, construction and maintenance of taxi strips, plane dispersal shelters, covered revetments and tunnels and the speedy establishment of underground as well as dispersed installations for quarters, communications and construction apparatus were undertaken with the time of completion set for the middle of August. The location of the established bases at that time was as follows:

Location

Land-plane Bases

Seaplane Bases

Total

Hokkaido

6

1

7

Ou District

6

2

8

Kanto District

11

4

15

Chubu District

9

2

11

Kinki District

4

3

7

Chugoku District

3

2

5

--17--

Shikoku District

2

7

Kyushu District

19

7

26

Korea

7

1

8

Total

70

24

94

Maintenance of secret basest Construction of secret bases (called pasture ground) throughout the country for dispersal and readiness, or for attack bases, of the special attack units, which consisted primarily of training land planes, and maintenance of the western and eastern parts of the mainland by the target dates of 15 August and the end of September respectively, were planned and carried out. In view of the nature of the above bases, attention was paid to camouflage from the time of construction. They were maintained by taking special precautionary measures, such as leaving houses and trees in the secret bases intact until the air units advanced to the bases. The location of the secret bases known as pasture ground was as shown on Chart 6. Chart 7 gives the location of bases prepared for Model 43 Oka special planes in accordance with Yokosuka Naval District Top Secret Order No 496, in May 1945.

In addition, the Osaka Guard District planned to establish six catapults and prepare 25 sheds of Oka bombs in the vicinity of Tanabe.

d. Measures to increase the effectiveness of the special attack planes: Special attack planes were used for the first time in the Philippines in 25 October 1944. They produced not only psychological effects, but also actually inflicted heavy damage on the enemy. This

method of attack was made possible by the imbued patriotism of all com-

--18--

Chart 6-a

Chart Showing Secret Bases (Called Pasture-Ground)

District

Name

Runway

Prefecture, County, Village

Remarks

Yokosuka

Yodanhara

50 x 1,200; extension made to the east & west

Miyagi Ken, Kurihara Gun, Fujisato Mura

Generally completed at the end of August

Babadaira

60 x 800; SN

Fukushima Ken, Adachi Gun, Oyama Mura

Generally completed

Miyota

60 x 800

Fukushima Ken, Tamura Gun, Moriyama Machi

Generally completed at the end of July

Asakawa

70 x 500; EW 30 x 600; SN

The Suigun Line (Iwagi Asakawa)

Generally completed

Ebigashima

60 x 800

Ibaragi Ken, Makabe Gun, Omura

Generally completed at the end of July

Ohatake (Fujisawa)

60 x 800

Ibaragi Ken, Niihari Gun, Fujisawa Mura

Generally completed

Katsuragi

60 x 800

Ibaragi Ken, Tsukuba Gun, Katsuragi Mura

Generally completed

Okabe

60 x 800

Ibaragi Ken, Inashiki Gun, Okada Mura

Generally completed at the end of August

Negata

(2d Kisarazu)

50 x 600

Chiba Ken, Kimitsu Gun, Negata Mura

Generally completed at the end of August. (Hitachi Aircraft Co (Hitachi Sha))

Oyana

(2d Atsugi)

100 x 1,800 NNW

Kanagawa Ken, Koza Gun, Ayase

Same as above

Iwamurada

50 x 600; NNW

Nagano Ken, Minami-saku Gun, Iwamurata Machi

Generally completed at the end of August

Chart 6-b

Chart Showing Secret Bases (Called Pasture-Ground)

(Cont'd)

District

Name

Runway

Prefecture, County, Village

Remarks

Yokosuka

Yoshioka

(2d Oi)

60 x 900; NNW

Shizuoka Ken, Oi, Wadaoka Machi

Generally completed

Bazu

50 x 600;

extension made

Aichi Ken, Nukada Gun, Miai Mura (TN Presumably Kawai Mura)

Generally completed

Iwatsu

Aichi Ken, Nukada Gun, Iwatsu Mura

Generally completed at the end of July. (Nakajima Aircraft Co (Nakajima Sha))

Takanoo (3d Susuka)

60 x 1,200; NW

Mie Ken, Kawage Gun, Takano Mura (TN Presumably Takanoo Mura)

Same as above

Meizuru

Takegata (TN

Presumably

Masugata)

60 x 800

Yamagata Ken, Mogami Gun, Yamuki Mura

Generally completed at the end of July

Tamanohara (TN Presumably Tamano)

60 x 800

Yamagata Ken, Kita-murayama Gun, Tamanohara Mura (TN Presumably Tamano Mura)

Same as above

Yonasawa

60 x 800

Yamagata Ken, Nishi-Murayama Gun, Shigematsu Mura (TN Presumably Takamatsu Mura)

Same as above

Urushiyama

300 x 1,000; SN

Yamagata Ken, Higashi-Murayama

Already established (Hitachi Aircraft Co (Hitachi Sha))

Chart 6-c

Chart Showing Secret Bases (Called Pasture-Ground)

(Cont'd)

District

Name

Runway

Prefecture, County, Village

Remarks

Maizuru

Tazu

50 x 700; extended to 1,200

Ishikawa Ken, Kashima Gun, Soma Mura

Generally completed at the end of July. (Nakajima Aircraft Co (Nakajima Sha))

Atago (Fukui)

50 x 700; extended to 1,200

Fukui Ken, Nibu Gun, Takano Mura (TN Presumably Yoshino Mura)

Generally completed at the end of July (Aichi Aircraft Co (Aichi Sha))

Shiga

60 x 1,000; NNE

Shiga Ken, Shiga Gun, Shimo-sakamoto Mura

Same as above

Hikone

30 x 600 (60 x 1,200)

Shiga Ken, Inuyama Gun

30 x 600 . . . completed at the end of July.

60 x 1,200 . . . completed at the end of August.

(Mitsubishi Aircraft Co (Mitsubishi Sha))

Ayabe

30 x 600; EW

Kyoto Fu, Ikaruka Gun, Ikuda Mura

Generally completed

Oshinotsu

30 x 600

Tottori Ken, Seihaku Gun, Oshinotsu Mura

Same as above

Naoe

30 x 600; SW

Shinano Ken, Hinokawa Gun, Naoe Mura

Same as above

Osaka

Ichiba (2d Tokushima)

100 x 1,200; EW

Tokushima Ken, Awa Gun, Ichiba, Mura

Generally completed (Kawanishi Aircraft Co (Kawanishi Sha))

(2d Yamato)

Chart 6-d

Chart Showing Secret Bases (Called Pasture-Ground)

(Cont'd)

District

Name

Runway

Prefecture, County, Village

Remarks

Kure

Kuniyasu (Kabe)

60 x 1,200; KE

Hiroshima Ken, Takata Gun, Neno Mura

Generally completed at the end of August

Shimokawara

30 x 600; NNE

Hiroshima Ken, Saeki Gun, Sakagami Mura

Same as above

Shiroyama (Iwakuni)

30 x 600; 2 runways, NE

Yamaguchi Ken, Kuga Gun, Fujisawa Mura (TN Presumably Fujikawa Mura)

Same as above

Osaba

30 x 600; NNW

Yamaguchi Ken, Yoshiki Gun, Osaba Mura

Same as above

Akago

30 x 600; NW

Yamaguchi Ken, Mine Gun, Akago Mura

Same as above

Tano

30 x 600; NW

Shima Ken, Shuso Gun, Tano Mura

Same as above

Takenoshita

30 x 600; EW

Ehime Ken, Onsen Gun, Haishi Mura

Same as above

Kamimurashima

30 x 600; EW

Shima Ken, Kita Gun, Sugeta Mura

Same as above

Niida
(2d Kochi)

100 x 1,800; EW

Kochi Ken, Kami Gun, (TN Presumably Takaoka Gun), Niida Mura

Generally completed at the end of August

Kubokawa
(3d Kochi)

60 x 1,200; SN

Kochi Ken, Takaoka Gun, Kubokawa Machi

Same as above

Saikawa

30 x 600; NE

Fukuoka Ken, Miyako Gun, Saikawa Mura

Same as above

Chart 6-a

Chart Showing Secret Bases (Called Pasture-Ground)

(Cont'd)

District

Name

Runway

Prefecture, County, Village

Remarks

Kure

Nakatsu

30 x 600; HW

Oita Ken, Shimoge Gun, Tsurui Mura

Same as above

Kusaji

30 x 600; EW

Oita Ken, Nishi-Kunisaki Gun, Kusaji Mura

Same as above

Usuki

30 x 600; NS

Oita Ken, Kita-amabe Gun, Usuki Machi

Same as above

Totsugi

80 x 1,500; NE

Oita Ken, Oita Gun, Totsugi Mura

Same as above

2d Iwakuni

50 x 520; NS

Yamaguchi Ken, Kuga Gun, (TN Presumably Kumage Gun), Marifu Mure

The northern part adjoins the airfield

Sasebo

Naokata

30 x 600; NNW

Fukuoka Kan, Onga Gun, Tonno Mura

Emergency runway: generally completed on 15 July

Tatara

28 x 1,000; NS

Fukuoka Ken, Chikushi Gun, Kasuga Mura

Generally completed

Ogi

30 x 600; ENE

Saga Ken, Ogi Gun, Ogi Mura

Same as above

Ainoura

30 x 600; ESS

Nagasaki Ken, Kita-matsuura Gun, Ainoura

(Drill ground of marine corps)

Kawatana

30 x 600; EW

Nagasaki Ken, (Higashi)-Sonoki Gun, Kawatana Cho

Generally completed (Factory site)

Chart 6-f

Chart Showing Secret Bases (Called Pasture-Ground)

(Cont'd)

District

Name

Runway

Prefecture, Country, Village

Remarks

Sasebo

Shimabara

30 x 600; NNW

Nagasaki Ken, (Shimabara Shi), Shimabara

Generally completed

Onsen

30 x 390; ENE

Nagasaki Ken, Minami-takaki Gun, Obama Machi

Same as above

Takematau (Shinomura)

50 x 1,350; NNW

Nagasaki Ken, Higashi-sonoki Gun, Takamatsu Cho

50 x 950

Generally completed

Makinohara

60 x 900; NW

Kagoshima Ken, Airs Gun, Shikine Mura

Generally completed

Nagao

(Iwakawakaido)

60 x 1,200; NE

Kagoshima Ken, Kimotsuki Gun, Kasanohara Mura

Generally completed

Yokosuka

Kantatsu

30x600

Ibaragi Ken, Niihari Gun, Ishida Mura

Already established. Runway of the Tsuchiura Air Group

Chart 7

Preparation of Bases for Special Planes Bases for Model 43 Oka

(Yokosuka Naval District Top Secret Operational Order No 496, 20 May 1945)

Name of Base

Catapults

Completion Date

Sheds of Oka Bombs

Completion Date

Izu Peninsula

8

Middle of August

5

Middle of August

20

Middle of September

20

Middle of October

Southern Boso Peninsula

6

Middle of August

Same as above

Same as above

Eastern Boso Peninsula

6

Middle of August

Same as above

Same as above

Vicinity of Tsukuba

6

Middle of September

5

Middle of September

20

Middle of October

20

Middle of November

Miura Peninsula

3

Middle of July

5

Middle of July

10

Middle of November

Vicinity of Oi

6

Middle of October

5

Middle of September

20

Middle of October

Vicinity of Toba

6

Middle of October

Same as above

Same as above

bat men from commanders down to crewmen. Therefore, the High Command exerted efforts to produce as highly effective special attack planes as possible. The following are the orders and results concerning experiments and research on special attack planes:

Front Chief, First Bureau, Naval General Staff, Imperial General Headquarters

To: Chief, Navy affairs Bureau, Navy Ministry

Chief, General Affairs Bureau, Navy Aeronautical Department

Chief, General Affairs Bureau, Navy Technical Department

Request Concerning an Increase in the Effectiveness of Special Attack Planes

In view of the great difference in air strength between the enemy and ourselves and the degree of training of Navy airmen, greater importance should be attached to special attack planes. Judging from past combat experiences and statements of prisoners of war, it is impossible to inflict a fatal blow on large enemy vessels, because the equipment and methods used by the present special attack planes are inadequate for complete penetration. Therefore, it is requested that the following matters be immediately studied in order to increase their effectiveness. 1. It is requested that a test be conducted immediately in order to deliver successful bomb hits below the waterline of enemy vessels by special attacks:

20 May 1915

a. Stern attack

--19--

(Even if the bomb does not hit and explode at the ship's bottom, there is a strong probability that it will reduce mobility by hitting the armorless stem near the water line.)

b. Side attack

2. Method of increasing the approach speed of special attack planes: It is requested that the wings of the special attack planes be removed during the dive in order to achieve a sudden increase in speed and to minimize damage by enemy interception and defensive fire. Furthermore, this will increase the effect of the hits by increasing the approach speed. It is requested that this procedure be applied to the Ki-115 and that measures be taken immediately for their mass production.

3. It is requested that tests of V-head bombs be completed immediately and that they be supplied to the operational forces.

4. Testing of explosive charges to increase bursting effect: It is requested that methods of producing a more powerful bursting effect, to be employed by the special attack plane by loading it with liquid oxygen, hydrogen peroxide or yellow phosphorous, be studied and tested.

5. It is suggested as a method of using these new charges as substitutes for bombs, that the obsolete torpedo air chamber (re-

--20--

move rear part, including the torpedo engine room) be used by filling it with hydrogen peroxide, et cetera.

As requested, tests of explosive charges were held at Takeyama and Kure. The results of these tests are shown on Charts 8 and 9.

A request for testing the effectiveness of special attack planes by using a real warship as a target and catapulting special attack planes from catapults was submitted by the Naval General Staff in late May. It was first decided to use two warships, the Ise and the Hyuga. However, in the test, due to various circumstances, the Aso was decided upon.

Except for the Type 0 Fighter, with a 500 kg bomb, and the land bomber (Francis) with two 800 kg bombs, which had actually been used in combat, there were no other planes tested prior to termination of the war. Even the above, two tests were mainly the result of the efforts of the combat forces.

Surface and underwater special attack weapons: The Japanese Navy, which had long been accustomed to building large vessels and big guns, began to concentrate on the construction of small vessels and craft from the time of the Revised Fifth Replenishment Plan. At the same time attention was shifted to mass production of special attack weapons.

Surface and Underwater Special Attack Weapons Preparation Plan

Apr

May

Jun

Jul

Aug

Sep

Total

Submarines (Small)

2

4

8

13

13

40

KORYU (Midget submarine)

27

33

50

100

150

180

540

--21--

Chart 8

Condensed Report of the Results of Tests at Takeyama Base

Date

Type of Aircraft

Bombs

No. of Bombs

Thickness
of
Armor Plate

Angle
of Incidence

Target Angle

Speed

Results

1

17 Jul

Type 93 Intermediate Trainer

250 kg land bombs

1

12

30

0

55

Penetration (After action of firing assembly)

2

21 Jul

Shiragiku Utility Trainer

250 kg land bombs

2

12

30

0

53

Same as above

3

24 Jul

Type 9 Fighter

500 kg general purpose bombs

1

12

30

0

55

Same as above

4

28 Jul

Shiragiku Utility Trainer

250 kg land bombs

2

8

60

0

55

Ricochet (After action of firing assembly)

5

3 Aug

Shiragiku Utility Trainer

250 kg land bombs

1

8

0

45

55

Penetration (After action of firing assembly)

6

15 Aug

Type 93 Intermediate Trainer

250 kg land bombs

1

8

60

0

80

Same as above

Chart 9

Results of Ko-Go Tests at Kure Navy Yard

Warship Used

Type of Bomb Tested

Installation

Results

1

Aso

(Medium-Class Aircraft Carrier)

(Not completed, had no flight deck Displacement Tonnage at that time was 10,000 tons)

Type A Torpedo Warhead (V-Head)

Angle of incidence, 15 deg on the forelift

Only small holes were Caused on both side plates; operation of the warship was hardly affected

2

Type 4 Torpedo Warhead (V-Head)

On the tower whose height is equal to the distance between the shelter deck and the flight deck (in the center of the warship)

(Angle of incidence, 45 deg)

The speed remained unchanged and navigation was possible in spite of the damage suffered on the shelter deck and the upper deck

3

500 kg General Purpose Bomb

On the armor deck over the fore magazine room (Angle of incidence, 45 deg)

The armor deck sank and starboard plate was holed 6 m x 12 m

Flooding; 2,070 tons

A

V Bomb (800 kg Oka Model 22)

On the lower deck near the after lift (Angle of incidence 45 deg)

Hole 3 m x 7 m was caused on the armor deck.

There was no flooding in spite of serious damage

5

Sakura

Bomb

(Army)

On top of the tower whose height is equal to the distance between the shelter deck and the flight deck. (On the aftermost part of the warship) (Angle of incidence 20 deg)

Hole at the bottom of the warship was 6.9 m x 8 m

Flooding, 150 tons

Summary

1. Effectiveness of the air burst of the Type 4 torpedo head is comparatively small and therefore, its value as a special attack weapon is small.

2. The V bomb had a greater penetration power than does the general purpose bomb. Therefore, it must be prepared immediately and tested for its effectiveness as compared to the general purpose bomb.

3. Although the Sakura bomb might inflict comparatively small damage to a ship, it is recognised that the bomb can inflict fatal damage to a war ship, if it hits, for instance, the magazine room.

4. In general, the penetration bomb can destroy that part of the object in the course of the flame.

However, it does hardly any damage to parts not on this course.

 

 

Apr

May

Jun

Jul

Aug

Sep

Total

KAIRYU (Midget submarine)

100

95

105

150

150

150

750

KAITEN (Human torpedo)

73

83

93

To be decided later

249

SHINYO (surface craft)

Model 1

300

600

600

600

600

600

3,450

Model 5

150

However, because of various successive bottlenecks in the execution of the plan, only approximately half of the plan was realized. Actual production was as shown on Chart 10.

The organization and disposition of surface and underwater special attack units for the decisive battle of the Homeland are shown on the following charts:

Chart 11: Table of Organization of Special Attack Squadrons

Chart 12: Chart Showing the Location of Special Attack Bases

Chart 10

Results of Surface and Underwater Special Attack Weapons Preparation

Production

Total

Percentage

 

April

May

June

Completed

Plan

Completed

Plan

Completed

Plan

Completed

Plan

 

Submarines (Small)

2

2

2

4

4

6

67

 

KORYU (Midget submarine)

12

27

12

33

20

50

44

110

40

 

KAIRYU (Midget submarine)

9

100

42

95

74

105

125

300

42

 

KAITEN (Human torpedo)

66

73

42

83

51

92

159

249

64

 

SHINYO (Suicide surface craft)

Type 1

68

300

316

450

284

450

668

1,200

56

 

Type 5

181

150

167

150

111

150

459

450

102

 

Chart 11-a

Table of Organization of Special Attack Squadrons

Force

Vessels

Attack Units

Other Units

Yokosuka Naval

District Force

1st Special
Attack
Squadron

Destroyer Sawakase

Yokosuka Attack Unit

Yokosuka Naval Defense Corps

Frigates Amakusa, Shizaka

11th " "

Frigate No 37

15th " "

Minesweeper No 27

16th " "

Subchasers Nos 42, 47 & 51

18th " "

Light

Minelayer Kamijima

71st " "

7th Special
Attack
Squadron

Minesweeper No 1

12th Attack Unit

Onagawa Naval Defense Corps

Subchasers Nos 33 ft 48

14th " "

17th " "

4th Special
Attack
Squadron

Submarine

Tender Komahashi

13th Attack Unit

Ise Naval Defense Corps

Frigates Nos 4, 45 & 50

19th " "

Subchasers Nos 14 & 44

Kure Naval District Force

2d Special
Attack
Squadron

Okami Attack Unit

Hikari " "

Hirao " "

Kasado " "

81st " "

8th Special
Attack
Squadron

34th Minesweeper Division

21st Attack Unit

Saeki Air Group

23d " "

Saeki Naval Defense Corps

24th " "

Osaka Guard District Force

6th Special
Attack
Squadron

Frigates Nos 30 & 190 Petrol Boat No 104

22d Attack Unit

Kii Naval

Defense Corps

Chart 11-b

Table of Organization of Special Attack Squadrons

(Cont'd)

Force

Vessels

Attack Units

Other Units

Sasebo Naval District Force

3d Special

Attack

Squadron

Kawadana Attack Unit

31st " "

34th " "

5th Special

Attack

Squadron

Subchaser No 49

32d Attack Unit

33d " "

35th " "

Maizuru Naval District Force

Maizuru Attack Unit

Chinkai Guard District Force

42d Attack Unit

Combined Fleet

10th Special

Attack

Squadron

Submarine HA-109

101st Attack Unit

Submarine HA-111

102d " "

Oura " "

Shozushima Attack Unit

Seventh Fleet

36th Attack Unit

Chart 12-a

Location of Special Attack Bases 15 August 1945

Chart 12-b

Location of Special Attack Bases 15 August 1945

(Cont'd)

Chart 12-c

Location of Special Attack Bases 15 August 1945

(Cont'd)

APPENDIX I

Major Naval Arms and Weapons Produced from January 1944 to Cessation of Hostilities

Appended Chart 1-a

Naval Craft Completed After January 1944 (Number and Displacement)

Type of Naval Craft

Class and Displacement

1944

1945

Incomplete

First Quarter

Second Quarter

Third Quarter

Fourth Quarter

First Quarter

Second Quarter

Third Quarter

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Aircraft Carrier

No 110 Class

62,000

1 62,000

Taiho Class

30,360

1 (TN Number of craft)

30,360 (TN Displacement)

Unryu Class

17,500

2 35,000

1 17,500

1 17,500

Unryu Class

17,460

1 17,460

Hiryu Class

17,260

1 17,260

Ibuki Class

12,500

1 12,500

Monthly total

1 30,360

2 35,000

1 17,500

1 82,000

4 64,720

Quarterly total

1 30,360

2 35,000

2 79,500

4 64,720

Cruiser

Agano Class

6,500

1 6,500

Quarterly total

1 6,500

Destroyer

Yugumo Class

2,040

1 2,040

1 2,040

1 2,040

Akizuki Class

2,700

1 2,700

1 2,700

2 5,400

1 2,700

1 2,700

Matsu Class

1,260

1 1,260

3 3,780

1 1,260

3 3,780

4 5,040

1 1,260

3 3,780

1 1,260

3 3,780

1 1,260

6 7,560

1 1,260

3 3,780

1 1,260

4 5,040

Monthly total

1 2,040

2 4,740

1 1,260

2 4,740

3 3,780

1 1,260

3 3,780

4 5,040

1 1,260

3 3,780

3 6,660

4 6,480

1 1,260

6 7,560

2 3,960

3 3,780

1 1,260

4 5,040

Quarterly total

3 6,780

6 9,780

8 10,080

7 11,700

11 15,300

6 9,000

4 5,040

Submarine

I-400 Class

3,430

1 3,430

1 3,340

1 3,430

1 3,430

I-351 Class

2,650

1 2,650

1 2,650

I-13 Class

2,400

1 2,400

1 2,400

1 2,400

I-1 Class

2,390

1 2,390

I-16 Class

2,180

1 2,180

1 2,180

1 2,180

I-15 Class

1,950

1 1,950

Appended Chart 1-b (Cont'd)

Naval Craft Completed After January 1944 (Number and Displacement)

Type of Naval Craft

Class and Displacement

1944

1945

Incomplete

First Quarter

Second Quarter

Third Quarter

Fourth Quarter

First Quarter

Second Quarter

Third Quarter

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Submarine

I-52 Class

2,100

1 2,100

1 2,100

I-54 Class

1,950

1 1,950

1 1,950

1 1,950

I-361 Class

1,470

2 2,940

1 1,470

1 1,470

4 5,880

1 1,470

2 2,940

I-372 Class

1,660

1 1,660

1 1,660

1 1,660

I-201 Class

1,000

2 2,000

1 1,000

5 5,000

RO-35 Class

965

2 1,930

1 965

1 965

1 965

1 965

1 965

1 965

RO-100 Class

429

2 858

HA-101 Class

370

1 370

3 1,110

3 1,110

1 370

1 370

1 370

2 740

HA-201 Class

320

2 640

2 640

1 320

5 1,600

22 7,040

I-12 Class

2,200

1 2,200

Monthly total

5 4,738

3 5,245

2 2,915

1 2,100

4 6,105

2 3,420

3 4,615

4 5,880

4 6,565

2 2,940

3 2,995

5 6,940

2 6,080

5 3,110

2 2,770

1 1,660

3 1,010

3 1,040

3 4,120

5 1,600

34 25,310

Quarterly total

10 12,898

7 11,625

11 17,060

10 12,875

9 11,960

7 4,310

8 5,720

34 25,310

Minelayer

Minomo Class

3,000

1 3,000

Quarterly total

1 3,000

Frigate

Etorofu Class

870

1 870

Mikura Class

940

1 940

2 1,880

1 940

2 1,880

2 1,880

2 1,880

1 940

1 940

3 2,820

5 4,700

3 2,820

3 2,820

4 3,760

4 3,760

1 940

4 3,760

No 1 Class

750

2 1,500

4 3,000

4 3,000

4 3,000

3 2,250

4 3,000

5 3,750

5 3,750

5 3,750

2 1,500

3 2,250

2 1,500

3 2,250

4 3,000

1 750

2 1,500

4 3,000

No 2 Class

740

3 2,220

9 6,660

1 740

2 1,480

2 1,480

5 3,700

5 3,700

6 4,440

4 2,960

7 5,180

3 2,220

5 3,700

6 4,440

2 1,480

2 1,480

1 740

5 3,700

Monthly total

1 940

8 6,470

13 9,660

6 4,680

4 3,360

4 3,360

6 4,480

9 6,890

10 7,640

14 11,010

9 6,710

17 13,630

8 6,540

11 8,770

12 9,700

9 7,490

4 3,000

1 750

5 3,920

1

13 10,460

Quarterly total

22 17,070

14 11,400

25 19,410

40 31,350

31 25,010

14 11,240

6 4,660

13 10,460

Naval Transport

No 1 Class (TN APDI)

1,500

1 1,500

3 4,500

3 4,500

3 4,500

3 4,500

3 4,500

2 3,000

1 1,500

1 1,500

1 1,500

1 1,500

No 101 Class (TN LSMI)

890

2 1,780

4 3,560

2 1,780

3 2,670

4 3,560

4 3,560

3 2,670

12 10,680

5 4,450

3 2,670

1 890

3 2,670

1 890

1 890

1 890

4 3,560

Appended Chart 1-b (Cont'd)

Naval Craft Completed After January 1944 (Number and Displacement)

Type of Naval Craft

Class and Displacement

1944

1945

Incomplete

First Quarter

Second Quarter

Third Quarter

Fourth Quarter

First Quarter

Second Quarter

Third Quarter

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Naval Transport

Monthly total

2 1,780

5 5,060

2 1,780

3 2,670

7 8,060

4 3,560

6 7,170

15 15,180

5 4,450

6 7,170

4 5,390

3 2,670

2 3,000

1 890

2 2,390

1 1,500

2 2,390

5 5,060

Quarterly total

7 6,840

12 12,510

25 25,910

15 17,010

6 6,560

3 3,890

2 2,390

5 5,060

Minesweeper

No 19 Class

630

1 630

2 1,260

1 630

1 630

Quarterly total

1 630

3 1,890

1 630

Subchaser

No 13 Class

440

2 880

3 1,320

1 440

1 440

1 440

1 440

Quarterly total

5 2,200

2 880

1 440

1 440

Light Minelayer

Ajiro Class

720

1 720

Kamishima Class

766

1 766

1 766

Monthly total

1 720

1 766

1 766

Quarterly total

1 720

1 766

1 766

Special Duty Ship

Hario Class (AO)

18,500

1 18,500

Ohama Class (target ship)

2,670

1 2,670

1 2,670

Monthly total

1 18,500

1 2,670

1 2,670

Quarterly total

1 18,500

1 2,670

1 2,670

Auxiliary Patrol Vessel

No 1 Class

238

2 476

4 952

2 476

6 1,428

4 952

5 1,190

4 952

26 6,188

Quarterly total

6 1,428

12 2,855

9 2,142

26 6,188

Auxiliary Subchaser

No 1 Class

130

4 520

8 1,040

9 1,170

6 780

9 1,170

10 1,300

13 1,690

12 1,560

10 1,300

11 1,430

14 1,820

910

5 650

Quarterly total

21 2,730

25 3,250

32 4,160

Monthly total

12 7,078

23 17,205

35 55,225

16 10,600

25 19,745

28 20,990

30 17,795

36 60,280

43 35,725

35 39,030

37 90,975

37 52,030

23 25,090

21 16,616

25 21,872

16 15,976

17 10,718

9 4,602

16 12,386

11 6,292

88 120,214

Quarterly total

70 79,508

69 51,335

109 113,800

109 182,035

69 63,578

42 31,296

27 18,678

88 120,214

Remarks: The naval craft listed as incomplete refer to those not yet completed at the end of war and also those whose construction was suspended during the war.

Appended Chart 2

Transports and Freighters Completed After January 1944

Year

Month

Quarter

Freighter

Tanker

Others

Monthly total

Quarterly total

No

Tonnage

No

Tonnage

No

Tonnage

No

Tonnage

No

Tonnage

1944

Jan

First Quarter

28

56,520

11

36,470

3

15,250

42

108,240

203

514,840

Feb

45

89,100

13

38,370

58

127,470

Mar

72

183,430

27

89,570

4

6,130

103

279,130

Apr

Second Quarter

34

72,590

8

6,960

42

79,550

161

370,610

May

40

82,180

19

61,110

3

2,000

62

145,290

Jun

40

97,650

17

48,120

57

145,770

Jul

Third Quarter

33

50,620

17

55,270

3

2,000

53

107,890

180

398,470

Aug

33

38,820

24

71,890

57

110,710

Sep

40

52,050

29

127,320

1

500

70

179,870

Oct

Fourth Quarter

40

48,830

23

97,200

1

500

64

146,530

189

418,990

Nov

40

59,720

24

77,480

1

900

65

138,100

Dee

41

76,810

18

57,050

1

500

60

134,360

1945

Jan

First Quarter

31

63,170

16

51,000

3

10,500

50

124,670

130

386,320

Feb

36

101,930

12

50,920

48

152,850

Mar

27

85,080

3

13,720

2

10,000

32

108,800

Apr

Second Quarter

12

23,180

1

500

13

23,680

41

128,550

May

19

63,470

1

500

20

63,970

Jun

8

40,900

8

40,900

Jul

Third Quarter

11

36,580

11

36,580

18

56,401

Aug

7

19,821

7

19,821

Appended Chart 3-a

Aircraft Produced January 1944 - August 1945

Item

Year

1944

Month

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Type of Aircraft

Standard Planes

Carrier-borne fighters

1

363

269

362

339

327

300

278

367

224

994

966

889

Interceptors

2

35

67

75

117

58

116

127

117

125

177

291

369

Night fighters

3

25

18

18

35

40

40

27

35

40

61

115

102

Carrier-borne bombers

4

140

147

141

125

133

118

107

106

122

428

376

335

Carrier-borne attack bombers

5

30

25

39

36

36

57

79

85

76

94

129

240

Land-based reconnaissance planes

6

1

2

6

6

0

1

4

8

19

9

7

31

Land-based bombers

7

11

20

35

46

46

51

47

48

69

66

143

164

Land-based attack bombers

8

53

46

50

73

70

79

89

85

91

149

222

265

Patrol planes

9

1

1

2

1

2

3

3

3

3

4

6

9

Land-based transport planes

10

8

14

15

3

3

17

H

16

19

37

23

49

Seaplane fighters

11

9

10

10

0

0

0

0

0

0

29

0

0

Reconnaissance seaplanes

12

51

49

51

53

53

62

52

59

40

151

168

151

Appended Chart 3-b

Aircraft Produced January 1944 - August 1945

(Cont'd)

1944

1945

Japanese Designation of Aircraft (Factory)

Oct

Nov

Dec

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

1

339

360

268

251

167

247

267

285

208

153

101

Type-0 fighter (Nakajima and Mitsubishi)

967

665

760

254

2

129

121

95

89

97

140

128

101

56

44

8

Shiden (Kawanishi and Showa).

Raiden (Mitsubishi)

345

326

285

52

3

23

0

0

0

0

0

0

0

0

0

0

Gekko (Nakajima)

23

0

0

0

4

116

133

150

115

98

101

96

46

67

33

4

Suisei (Aichi and 11th Naval Air Depot) Type-99 (Aichi and Showa)

399

314

209

37

5

96

87

60

75

83

94

65

12

42

13

1

Tenzan (Nakajima). Ryusei (Aichi and 21st Naval Air Depot)

243

252

119

14

6

25

26

25

30

38

64

60

58

47

35

4

Saiun (Nakajima)

76

132

165

39

7

75

88

84

90

52

52

63

64

53

40

20

Ginga (Nakajima and Kawanishi)

247

194

180

60

8

109

108

60

55

60

50

65

31

25

1

0

Type-1 (Mitsubishi)

277

165

121

1

9

8

11

14

16

11

13

13

15

12

12

6

Tokai (Kyushu)

33

40

40

18

10

20

16

17

19

9

21

15

14

3

7

1

Type-0 (Showa)

53

49

32

8

11

0

0

0

0

0

0

0

0

0

0

0

Kyofu (Kawanishi)

0

0

0

0

12

61

70

73

49

47

32

22

16

11

4

4

Type-0 (Kyushu) Zuiun (Nippon Hikoki and Aichi)

204

128

49

8

Appended Chart 3-c

Aircraft Produced January 1944 - August 1945

(Cont'd)

Item

Year Month

1944

Type of Aircraft

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Standard Planes

Observation planes

1

50

40

35

30

35

30

15

6

0

125

95

21

Seaplane bombers

2

0

1

0

0

0

2

1

1

1

1

2

3

Flying boats

3

9

9

10

9

8

8

5

3

3

28

25

11

Total of combat aircrafts

4

786

718

849

873

811

884

848

939

852

2,353

2,568

2,639

Trainer

5

212

223

281

297

281

278

262

212

147

716

856

621

Total

6

998

941

1,130

1,170

1,092

1,152

1,110

1,151

999

3,069

3,424

3,260

Special-Type Planes

Oka, Model 11

7

10

10

Oka,

Model 22

8

Shusui

9

Kikka

10

Total

11

10

10

Grand Total

12

998

941

1,130

1,170

1,092

1,162

1,110

1,151

1,009

3,069

3,424

3,270

Appended Chart 3-d

Aircraft Produced January 1944 - August 1945 (Cont'd)

1945

Japanese Designation of aircraft (Factory)

Oct

Nov

Dec

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

1

0

0

0

0

0

0

0

0

0

0

0

Type-0 (21st Naval Air depot)

0

0

0

0

2

2

1

1

1

2

2

2

4

2

3

0

Seiran (Aichi)

4

5

8

3

3

3

4

6

4

2

2

3

0

0

0

0

Type-2, Soku (Kawanishi)

13

8

3

0

4

1,006

1,025

853

794

666

818

799

646

526

345

149

2,884

2,278

1,971

494

5

153

123

132

157

154

158

86

89

72

63

68

Type-0 training (Hitachi) Shiragiku (Kyushu) Type-93 intermediate trainer (Fuki and Nippon Hikoki)

408

469

247

131

6

1,159

1,148

985

951

820

976

885

735

598

408

217

3,292

2,747

2,218

625

7

50

95

93

160

197

150

(1st Air Technical Depot)

238

507

8

50

(1st Air Technical Depot)

50

9

1

4

(Mitsubishi and Nippon Hikoki)

1

4

10

1

(Nakajima)

0

1

11

50

95

93

160

197

151

51

4

238

508

51

4

12

1,209

1,243

1,078

1,111

1,017

1,127

885

735

649

412

217

3,530

3,255

2,269

629

Appended Chart 4A-a

Guns and Ammunition Produced January 1944 - August 1945

Weapons and Ammunition

Type of Guns

Caliber

1944

First Quarter

Jan

Feb

Mar

Guns

Flat

220mm

1

3

2

1

6

140mm

1

1

1

2

3

127mm

6

6

6

3

18

200mm short barrel and 120mm

33

51

46

4

130

Miscellaneous

5

2

3

2

7

Total

6

45

63

56

164

Dual
purpose
guns

127mm

7

30

30

30

90

120mm

8

62

81

95

238

100mm

9

8

12

2

22

80mm

10

8

2

8

18

Total

11

108

125

135

Total

12

153

188

191

532

Automatic
cannon and Machine gun

Machine guns

30mm

13

15

5

25

Appended Chart 4A-b

Guns and Ammunition Produced January 1944 - August 1945

(Cont'd)

1944

Second Quarter

Third

Quarter

Fourth Quarter

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

1

2

1

2

1

2

1

1

1

1

5

4

3

2

1

1

1

1

1

1

1

1

1

3

3

3

3

1

1

0

0

1

0

0

1

0

2

1

1

4

50

50

60

60

60

60

50

40

30

150

180

120

5

3

3

3

3

3

3

3

3

3

9

6

56

56

65

67

65

55

46

35

169

197

136

7

30

30

30

30

30

30

30

30

20

90

90

80

8

100

120

150

140

180

200

200

180

130

370

520

510

9

4

4

4

4

4

3

4

4

4

12

11

12

10

5

6

5

5

5

5

5

5

5

16

15

15

11

139

160

189

179

219

238

239

219

159

488

636

617

12

196

216

245

244

286

303

294

265

194

657

833

753

13

15

20

0

10

15

20

0

25

15

35

45

40

Appended Chart 4A-c

Guns and Ammunition Produced January 1944 - August 1945

(Cont'd)

1945

First Quarter

Second Quarter

Third Quarter

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

1

1

1

1

0

0

0

0

0

3

0

0

2

1

1

1

0

0

0

0

0

3

0

c

3

0

1

0

0

0

0

0

0

1

0

c

4

30

30

20

20

10

5

5

0

80

35

5

5

3

3

3

1

1

1

0

0

9

3

0

6

35

36

25

21

11

6

5

0

96

38

5

7

15

15

10

10

15

10

10

5

40

35

15

8

110

100

90

80

60

40

5

0

300

180

5

9

4

1

0

4

3

2

1

0

5

9

1

10

5

5

5

4

3

2

1

0

15

9

1

11

134

121

105

98

81

54

17

5

360

233

22

0

12

169

157

130

119

92

60

22

5

456

271

27

13

70

110

350

500

350

460

500

140

530

1,310

640

Appended Chart 4A-d

Guns and Ammunition Produced January 1944 - August 1945

(Cont'd)

Weapons
and
Ammunition

Type of Guns

Caliber

1944

First Quarter

Jan

Feb

Mar

Automatic

cannon

and

machine guns

Machine guns

25mm

1

800

1,000

1,000

2,800

20mm

2

770

1,195

1,710

3,675

13mm

3

600

740

780

2,120

7.9mm and 7.7mm

4

1,475

1,710

1,825

5,010

Total

5

3,660

4,650

5,320

13,630

Ammunitions

For flat guns

20mm and above

6

1,000

1,000

1,000

3,000

155mm and below

7

21,000

20,000

20,000

61,000

Total

8

22,000

21,000

21,000

64,000

For dual purpose gun

9

30,000

30,000

30,000

90,000

Total for flat and dual purpose guns

10

52,000

51,000

51,000

154,000

For automatic cannon and machine gun (thousand of rounds)

11

10,860

12,008

15,395

38,263

Appended Chart 4A-e

Guns and Ammunition Produced January - August 1945

(Cont'd)

1944

Second Quarter

Third Quarter

Fourth Quarter

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

1

1,500

1,700

1,700

2,000

2,000

2,000

2,200

2,200

2,000

4,900

6,000

6,200

2

1,240

1,520

2,340

2,340

3,375

3,080

3,660

3,830

3,490

5,100

8,795

10,980

3

900

1,000

1,150

1,080

1,300

1,320

1,455

1,605

1,590

3,050

3,700

4,650

4

1,430

1,545

1,550

1,685

1,265

1,210

1,500

1,195

1,030

4,525

4,160

3,725

5

5,085

5,785

6,740

7,115

7,955

7,630

8,815

8,655

8,125

17,610

22,700

25,595

6

1,000

1,200

800

500

500

500

500

0

0

3,000

1,500

500

7

15,000

10,000

10,000

5,000

5,000

5,000

3,000

2,000

0

35,000

15,000

5,000

8

16,000

11,200

10,000

5,500

5,500

5,500

3,500

2,000

0

38,000

16,500

5,500

9

30,000

40,000

40,000

40,000

40,000

50,000

50,000

60,000

60,000

110,000

130,000

170,00

10

45,000

51,200

50,800

45,500

45,500

55,500

53,500

62,000

60,000

148,000

146,500

175,500

11

13,543

13,390

12,306

12,728

12,210

11,193

11,391

11,466

10,419

39,239

36,131

33,276

Appended Chart 4A-f

Guns and Ammunition Produced January 1944 - August 1945

(Cont'd)

1945

First

Quarter

Second Quarter

Third Quarter

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

1

1,800

1,600

500

800

800

500

400

100

3,900

2,100

500

2

3,195

1,695

1,855

1,405

1,435

1,625

785

400

6,745

4,465

1,185

3

1,755

2,040

1,905

1,685

1,545

1,330

1,205

375

5,700

4,560

1,580

4

1,140

805

1,245

1,010

1,110

785

740

310

3,190

2,905

1,050

5

7,960

6,250

5,855

5,400

5,240

4,700

3,630

1,325

20,065

15,340

4,955

6

0

0

0

0

0

0

0

0

0

0

0

7

0

0

0

0

0

0

0

0

0

0

0

6

0

0

0

0

0

0

0

0

0

0

0

9

40,000

35,000

10,000

30,000

20,000

20,000

10,000

5,000

85,000

70,000

15,000

10

40,000

35,000

10,000

30,000

20,000

20,000

10,000

5,000

85,000

70,000

15,000

11

10,068

10,114

11,441

11,240

11,087

8,013

5,738

3,446

31,623

30,340

9,184

Remarks:

The guns listed here are those produced for naval craft, aircraft and naval land bases and do not include guns for land mobile combat use. However, the automatic cannon and machine guns and the ammunition to include those for land mobile combat use.

Appended Chart 4B

Land Mobile Combat Weapons Produced January - 1944 - August 1945

Year

1944

1945

Month, Quarter

Jan
to
Dec

Jan
to
Mar

Second Quarter

Jul to Aug

Gun and Ammunition

Apr

May

Jun

120mm gun, short barrel, for land mobile combat

Unknown

Unknown

5

29

0

Unknown

34

Ammunition for 120mm short barrel, for land mobile combat

"

"

5,800

4,700

3,000

"

13,500

80mm mortar

"

"

393

345

200

"

938

Ammunition for 80mm mortar

"

"

37,000

37,000

70,000

"

144,000

200mm rocket gun

"

"

50

10

190

"

250

100mm antitank gun (rocket type)

"

"

0

5

50

"

55

80mm antitank gun (rocket type)

"

"

210

60

345

"

615

Ordinary rocket shell

"

"

2,500

3,400

5,500

"

11,400

Antitank rocket shell

"

"

1,000

500

500

"

2,000

Hand grenade

"

"

15,000

85,000

300,000

"

400,000

Remarks:

1. The weapons listed here are these for land mobile combat.

2. Since records for months other than April, May and June of 1945 are not available, nothing definite is known.

3. Land mobile combat weapons, other than those listed here, are chiefly rifles and pistols transferred from the Army, but their number is unknown because of a lack of records.

4. Re vehicular weapons, tanks were chiefly transferred from the Army and the rest were appropriated by the Munitions Ministry. Their number also is unknown.

Appended Chart 5

Gunpowder Produced After January 1944 (Quantity in Kilograms)

Year and Month

Quarter

Powder for Guns

Powder for Machine Guns

Propellants

Explosives

Total

1944

Jan

First Quarter

464

1,351

233

746

8

25

1,937

6,187

2,642

8,309

Feb

474

233

7

2,061

2,775

Mar

413

280

10

2,189

2,892

Apr

Second Quarter

452

1,426

347

1,002

59

194

2,156

6,803

3,014

9,425

May

487

335

65

2,297

3,184

Jun

487

320

70

2,350

3,227

Jul

Third Quarter

487

1,423

319

1,000

70

249

2,451

7,512

3,327

10,184

Aug

466

330

89

2,412

3,297

Sep

470

351

90

2,649

3,560

Oct

Fourth Quarter

444

1,318

355

1,079

116

336

2,632

7,902

3,5,47

10,635

Nov

452

354

110

2,697

3,613

Dec

422

370

110

2,573

3,475

1945

Jan

First Quarter

422

1,286

420

1,220

145

508

2,489

7,789

3,476

10,803

Feb

422

420

164

2,520

3,526

Mar

442

380

199

2,780

3,801

Apr

Second Quarter

317

930

155

688

262

818

1,907

6,220

2,641

8,656

May

319

236

279

2,538

3,372

Jun

294

297

277

1,775

2,643

Jul

Third Quarter

229

343

142

193

170

237

1,281

1,927

1,822

2,700

Aug

114

51

67

646

878

Appended Chart 6

Fuel Produced After January 1944

Year

and Month

Item

Aviation Gasoline

Heavy Oil

Unit

(Kilograms)

(Tons)

Quarter

1944 Jan

First Quarter

18,000

56,000

29,000

83,000

Feb

21,000

29,000

Mar

17,000

25,000

Apr

Second Quarter

20,000

60,000

25,000

80,000

May

20,000

27,000

Jun

20,000

28,000

Jul

Third Quarter

19,000

49,000

28,000

75,000

Aug

15,000

25,000

Sep

15,000

22,000

Oct

Fourth Quarter

15,000

49,000

22,000

71,000

Nov

19,000

29,000

Dee

15,000

20,000

1945 Jan

First Quarter

14,000

34,000

18,000

58,000

Feb

13,000

19,000

Mar

7,000

21,000

Apr

Second Quarter

8,000

17,000

20,000

59,000

May

3,000

19,000

Jun

6,000

20,000

Jul

Third Quarter

7,000

10,000

11,000

15,000

Aug

3,000

4,000

Appendix II

Agreement Between the Army and the Navy Concerning War Preparations for the First Half of Fiscal Year 1945

Army General Staff

Navy General Staff

1 April 1945

Deputy Chief, Army General Staff

Vice-Chief, Navy General Staff

I, General Principles

The war preparations of the Army and the Navy for the first half of the fiscal year 1945 will be accomplished in accordance with the following principles:

1. Priority will be given to the equipment of the Air Forces and the Special Attack Forces. Of the Army land forces (operational forces, including the 40 newly-organized divisions) and the Navy forces (excluding Air Force and Special Attack Forces), those which can be relied upon to display fighting power to repel the enemy during the decisive battle for the Homeland will be provided promptly with sufficient equipment. War preparations for the defense of surface communications routes will be restricted to a minimum, while other preparations will be executed in consonance with national power and within a limit which will not affect major war preparations.

2. Efforts will be made by both the army and the Navy to cooperate in their war preparations. In exchanging assistance, the Array will facilitate the Navy's procurement of aircraft and special underwater attack weapons for attacking enemy task forces. The Navy will assist the Army in its procurement of aircraft and ground weapons to be used in the local air defense of the Homeland.

3. The Supreme Command will maintain close contact with the Government and extend all-out support and cooperation to the latter in concentrating the resources of the entire nation for war purposes, as well as in building up such war preparations.

4. The planning of Array and Navy war preparations, (items, quantities, priority, et cetera) will be based on the principles enumerated herein and implementation of such plans will be carried out with a view to adequate realization of such plans.

II. Essentials of the Goal for Army and Navy War Preparations

1. The order of priority in war preparations by the Army and Navy will be as follows:

a. Aircraft and special attack weapons

(1) Aircraft and special air attack weapons. The position on the priority list to be determined separately.

(2) Underwater and special surface attack craft.

(a) Koryu midget submarines and small submarines.

(b) Kairyu midget submarines.

(c) Kaiten human torpedoes.

(d) Shinyo crash boats.

(3) A minimum number of simple base installations required for operating the above.

--ii--

b. Ground weapons.

(1) Antitank weapons.

(2) Weapons for use against heavy weapons, landing craft and large caliber machine guns.

(3) Close-range automatic weapons and anti-aircraft guns.

(4) A minimum number of simple ground combat fortifications required for operating the above.

c. Naval craft and weapons for severing the enemy's rear lines and for protecting friendly surface communications lines.

(1) Submarines.

(2) Light minelayers and mines.

(3) Coastal defense craft and depth charges. (4) Frigates.

d. Transports

(1) Navy transports.

(2) Large landing barges.

e. Fortifications and installations

(1) Base for general aircraft and special attack aircraft.

(2) General preparations for land combat.

f. Other items (clothing, materiel, medical and veterinary supplies)

Minimum requirements proportionate to Army and Navy strength estimated for September 1945.

To secure the necessary provisions, every possible measure

--iii--

will be taken with the nation's food supply taken into consideration. The Army and Navy will collaborate in providing various types of fuel and ammunition in the maximum quantity and in such proportion as to meet the requirements of the different weapons. Maximum efforts will be made in making preparations for chemical warfare. The essentials of this measure will be prescribed in a separate agreement.

2. Essentials concerning procurement and distribution of the principal weapons to the Army and the Navy for the first half of fiscal year 1945 will be determined in accordance with Charts 1 through 7.

--iv--

Chart 1-a

The Number of Aircraft to be Made Available During the First Half of Fiscal Year 1945

Outline of Plan

1. In procuring aircraft, the Army will give top priority to those planes which can be used for attacking enemy vessels, especially transports, and for defending strategic points of the Homeland; the Navy will place too greatest emphasis upon the procurement of those planes which can be used against hostile carrier task forces for the retention of air and sea superiority.

2. Both the Army and the Nary will convert all their planes into special attack planes, procure high priority aircraft and make every effort to ready the various types of aircraft by the middle of the current fiscal year.

3. To meet the minimum operational requirements, the any and the Navy will each procure more than 1,200 front-line planes a month. They will cooperate with each other to facilitate dispersion and transfer underground production facilities.

Classification

Type of aircraft

Minimum Requirements

Production Goal

Army Aircraft

Fighter

Type I fighter

1,390

1,600

Type IV fighter

2,500

3,000

KI-100 fighter

1,200

1,500

KI-102 fighter**

300

500

Type III fighter

300

Total

5,390

6,900

Bomber

Type IV bomber

700

1,200

KI-74 bomber

50

150

Total

750

1,350

Hq Recon Plane

Type 100 Hq recon plane

500

800

Transport Plane

KI-54 (or KI-110) transport plane

100

150

Chart 1-b

The Number of Aircraft to be Made Available Daring the First Half of Fiscal Year

(Cont'd)

Classification

Type of Aircraft

Minimum Requirement

Production Goal

Army Aircraft

Transport Plane

Type 100 transport plane

100

KI-105 transport plane

50

Total

100

150

Trainer

KI-54 (or KI-110) trainer

100

Type II advanced trainer

300

Type IV trainer

250

Total

650

Grand Total

6,740

10,000

Navy Aircraft)

Fighter

Shiden-Kai

2,400

2,400

Zero fighter

1,800

2,700

Kaiden-Kai

600

Saiun

300

300

Ginga

100

100

Total

4,600

6,100

Reconnaissance Plane Saiun

850

850

Attack Plane

Ginga

700

700

Ryusei

300

300

Renzan

50

100

Total

1,050

1,100

Patrol Plane

Type I land-based attack plane***

240

250

Tokai

250

Total

500

Chart 1-c

The Number of aircraft to be Made Available During the First Half of Fiscal Year 1945

(Cont'd)

Classification

Type of Aircraft

Minimum Requirements

Production Goal

Navy

Aircraft

Sea Reconnaissance Plane "Seiran"

80

Type I Transport Plane

320

Type Zero Transport Plane

Trainer

Land-based medium trainer

200

Utility trainer

200

Zero training fighter

350

Type 99 training bomber

100

Tokai trainer

200

Total

1,050

Grand Total

6,740

10,000

Notes: * Number of planes to be procured by all means. Most of the planes to be produced at dispersed, underground facilities.

** Types of KI - 202 fighters that must be acquired by any means are the Type A and C.

*** Type I land-based attack planes will also be used as torpedo bombers.

Chart 2-a

List of Special Attack Weapons to be Produced Daring the First Half of 1945 Fiscal Year

Weapons

Apr

May

Jun

Jul

Aug

Sep

Total

Responsibility
for
Procurement
(The one
marked
"*" will
be mainly
responsible)

Remarks

"KI" 115 Special Attack Plane

50

150

300

400

500

600

2,000

Army

Special Type Plane

2,000

Navy

Oka

300

300

300

300

300

300

1,800

Navy

Koryu Midget Submarine

35

35

50

100

150

180

540

Navy

Kairyu Midget Submarine

100

120

130

150

200

200

900

Navy

Maximum efforts will be made to increase production

Kaiten Human Torpedo

100

100

100

110

120

120

650

Navy

Small Submarine

1

5

8

13

13

40

Navy

Shusui

100

150

200

200

250

300

1,200

*Army Navy

To be allocated equally to the Army and the Navy

Chart 2-b

Weapons

Apr

May

Jun

Jul

Aug

Sep

Total

Responsibility
for
Procurement
(The one
marked
"*" will
be mainly
responsible)

Remarks

Shinyo Navy Crash Boat

600

600

600

600

600

600

3,600

Army *Navy

Maruhachi Army Crash Boat

500

500

1,000

1,000

3,000

Army

Fu Go Bomb carrying Balloon

1,000

1,000

1,000

3,000

Army

Notes 

1. In addition to the weapons mentioned in this table, 10,000 "Ke" rocket bombs, 1,000 "I Go" bombs and 300 "Kikka" suicide attack planes are scheduled to be procured during the first half of the current fiscal year. But the decision relative to their procurement will depend upon the results of research and examination.

2. Procurement of other weapons now under consideration will be determined and added to this table after the research results are made available.

Chart 3-a

Quantity of Land Combat Weapons to be Produced During the First Half of Fiscal Year 1945

Part 1. Firearms and Guns

Classification of Weapons

Quantity
to be
Procured

Distribution

Responsibility
for
Procurement
(The one
marked "*"
will be
mainly
responsible)

Remarks

Model 99 Rifle

540,000

Army

440,000

* Army

Navy

100,000

Navy

Sub-machine Gun

6,200

Army

Army

Pistol

26,000

Army

19,000

Army

24,000

Navy

7,000

Navy

2,000

Heavy Grenade Discharger

20,900

Army

18,000

Army

18,000

Navy

2,500

Navy

2,500

Light Machine Gun

10,300

Army

Army

Heavy Machine Gun

4,200

Army

3,500

Army

3,000

Navy

700

Navy

1,200

Battalion Gun

1,050

Army

Army

"Rota" Rocket Launcher

23,500

Army

13,500

Army

6,000 (70 mm)

Navy

10,000

Navy

17,500 (100mm, 80mm)

47mm antitank Gun

325

Army

Army

105mm Recoilless Gun

120

Army

Army

Type 41 Mountain Gun

230

Army

Army

Type 94 Mountain Gun

130

Army

Army

Field Gun (Models 90 & 95)

38

Army

Army

150mm Cannon, 150mm Howitzer

27

Army

Army

Chart 3-b

Quantity of Land Combat Weapons to be Produced During the First Half of Fiscal Year 1945

(Cont'd)

Classification of Weapons

Quantity to be Procured

Distribution

Responsibility
of
Procurement
(The one
marked "*"
will be
mainly
responsible)

Remarks

100mm Howitzer, 100mm Cannon

54

Army

Army

120mm Mortar

720

Army

Army

120mm Short Flat-trajectory Gun

800

Army

400

Navy

Navy

400

80mm Mortar

10,000

Army

5,000

Navy

Navy

5,000

Rocket Gun

4,300

Any

2,300

Army

(120 200mm guns and 180 400mm guns)

Navy

2,000

Navy

(4,000 200mm or 120 mm guns)

Rocket Bomb Launcher

10,000

Army

1,000

Navy

Production goal will be set at 200,000

Navy

9,000

Army

Model 98 Grenade Discharger

3,000

Army

Army

Tanks

300

Army

Army

Self -mobile powered Gun

310

Army

270

Army

270

Navy

40

Navy

40

Part 2. Close-Quarter Combat Weapons

Classification

Quantity

Distribution

Responsibility for Procurement

Flame Thrower

2,400

Army

2,100

Army

2,100

Navy

300

Navy

300

Chart 3-c

Quantity of Land Combat Weapons to be Produced During the First Half of Fiscal Year 1945 (Cont'd)

Classification

Quantity

Distribution

Responsibility for Procurement

Antitank Mine

40,000

(5-kg hemispherical)

Army

Army

(2-kg conical)

(type 3 hand mine)

Yardstick Mine

200,000

Army

100,000

Amy

90,000

Navy

100,000

Navy

110,000

Small-type Mine (Assault)

150,000

Navy

150,000

Navy

 

Conical Hand Mine

100,000

Army

50,000

Navy

Navy

50,000

Hand Grenade

500,000

Amy

250,000

Amy

125,000

Navy

250,000

Navy

375,000

Molotov Cocktail Incendiary (Smoke) Grenade

300,000

Army

180,000

Amy

180,000

Navy

120,000

Navy

120,000

Part 3. Land Transport Weapons

Classification

Quantity

Distribution

Responsibility for Procurement

Tractor

210

Amy

Amy

Armored Troop Carrier

350

Amy

Amy

Track

6,100

Army and Navy To be fixed according to the else of the ground force

Army

5.100

Navy

1,000

Chart 3-d

Quantity of Land Combat Weapons to be Produced During the First Half of Fiscal Year 1945 (Cont'd)

Classification of Weapons

Quantity to be Procured

Distribution

Responsibility for Procurement

Amphibious Motor Transport

270

Army

Army

Small-type Track

1,100

Army and Navy

To be fixed according to the size of the ground force

Army

100

Navy

1,000

Trailer

620

Army

Army

Army Transport Car

To be determined separately

Army and Navy

To be fixed according to the size of the ground force

Army

3,000

Navy

To be determined separately

Carts

To be determined separately

Same as above

Army

3,600

Navy

To be determined separately

Part 4. Simple Weapons

To be fixed separately.

Remark: Distribution of ground weapons to the Army and the Navy will be made through a separate channel in order to best meet the war situation and will be based on practical consideration of the ground warfare of the Army and the Navy.

Chart 4-a

Production of Vessels During the First Half of Fiscal Year 1945 (For Escort, Transportation and Traffic Interruption Warfare)

Classification

Completion Expected During the First Half

Maintenance and Distribution

Destroyers

Tei

10

Navy

Submarines

Ko

2

Tei

1

Special

2

Supply

1

High speed

4

Coast Defense Ship's

Ko

20

Hei

Tei

Navy Transports

1st class

4

Navy and Army

2d class SB Type Landing craft

9

Bombardment Target Ship

1

Navy

Minelayer and Concurrently Target Ships

2

Navy

Chart 4-b

Production of Vessels During the First Half of Fiscal Year 1945 (For Escort, Transportation and Traffic Interruption Warfare)

(Cont'd)

Classification

Completion Expected During the First Half

Maintenance and Distribution

Minelayers

6

Including 4 converted merchant vessels

Coast Defense Boats

Ko

6

Navy

Otsu

18

Special Patrol Boats

40

Large Landing Barges

Special

30

Army

Steel

1,350

Army 900, Navy 450

Wood

1,850

Army 900, Navy 900

Amphibious

30

Navy

Engined Barges

360

Army

Small Transport Barges

400

Folding Boats

600

Type 1 Submersible Transport Craft

30

Remarks: Naval transports, submersible transports and barges shall be employed jointly by the Army and the Navy.

Chart 5-a

Antiaircraft Equipment to be Produced in the First Half of 1945 Fiscal Year

Classification

Quantity (Ammunition)

Antiaircraft Gun

For Army Land Defense

Model-88, 70 mm antiaircraft gun (Includes those for mounting on airplanes.

1160 (210,000 rounds)

Model-4, 70mm antiaircraft gun

200 (190,000 rounds)

80mm antiaircraft gun

240 (360,000 rounds)

120mm antiaircraft gun

95 (50,000 rounds)

150mm antiaircraft gun

5 (3,000 rounds)

For Nary Land Defense and for Vessels

Model-1, 127mm antiaircraft gun

30

500 rounds per gun

127mm antiaircraft gun

100

500 rounds per gun

120mm antiaircraft gun

410

400 rounds per gun

Model-98, 100mm antiaircraft gun

50

500 rounds per gun

Total

1,350

Chart 5-b

Antiaircraft Equipment to be Produced in the First Half of 1945 Fiscal Year

(Cont'd)

Classification

Quantity ([Estimated])

Antiaircraft Machine Gun

25mm antiaircraft machine gun

7,200

3,500 rounds per gun

20mm antiaircraft machine gun

(Type-4 twin mount)

900 (30,000,000)

13am antiaircraft machine gun

1,00

4,000 rounds per gun

40mm antiaircraft machine gun

560

4,000 rounds per gun

Searchlight

1.5 m reflector

230

2 m reflector

106

Antiaircraft Balloon

Type 1

10

Type 2

175

Small Sound Locator

110

80mm Barrage Mortar Shell

(300,000 rounds)

Antiaircraft Kits

1,600

Notes:

Employment of antiaircraft firearms for land defense shall be coordinated between the Army and the Navy.

Chart 6

Antisubmarine Weapons to be Constructed in the First Half of Fiscal Year 1945

Classification

Quantity

Distribution

Responsibility for Procurement

Sonar Equipment

2,000

Navy

4

Navy

Antisubmarine Radar

1,200

Army

200

Navy

1,000

Magnetic Radar for Aircraft

1,500

Army

300

Navy

1,200

Mine

Ordinary

30,000

Navy

For Beaches

20,000

Navy

Depth Charge

50,000

Army

10,000

Army

10,000

Navy

40,000

Nary

40,000

Chart 7

Fuel and Powder to be Produced in Japan, Manchuria and China

Classification

Quantity

Remarks

For Fiscal Year 1945

For the First Half of Fiscal Year 1945

Liquid Fuel

Aviation gasoline

60,000 kl

26,000 kl

Ordinary gasoline

50,000 kl

23,000 kl

Alcohol

400,000 kl

120,000 kl

Methanol

50,000 kl

20,000 kl

Heavy oil

Heavy oil for Navy use

250,000 kl

120,000 kl

Heavy oil for civilian use

160,000 kl

60,000 kl

Kerosene

130,000 kl

50,000 kl

"RO" - Go Fuel

40,000 tons

10,000 tons

Powder (Explosive)

Powder

70,000 tons

Army 10,000 ton

Navy 25,000 ton

Details of the allotment of powder and explosive to be used in the first half of fiscal year 1945 shall depend upon the distribution of weapons.

Explosive charges

80,000 tons

Army 20,000 tons

Navy 20,000 tons

Notes:

1. The distribution is determined separately.

2. Measures shall be jointly taken by the Army and the Navy to drastically increase the production of turpentine extracted from pine roots and other oils which are not mentioned in this table.

Appendix III

Naval General Staff Secret Document No 31

Data: 6 April 1945

Subject: Conference on War Preparations in the First Half of Fiscal Year 1945

From: Vice Chief of the Naval General Staff

To: Vice Minister of the Navy

In order to cope with the recent critical situation, it is requested, that arrangements be made to carry out immediately and resolutely the plans appended hereto concerning this subject matter. Relative to the conference, it is requested that the details be worked out by competent persons.

An agreement on the war preparations to be made during the first half of fiscal year 1945 was made between the Naval General Staff and Army General Staff Headquarters, as described in the annex.

Distribution:

Chief of Naval Aeronautical Department.

Chief Of Naval Technical Department.

Chief of Naval Civil Engineering Department.

Annex

I. Plan for War Preparations

A. In the first half-year period, efforts will be made to build

defense positions around Japan from which the advancing enemy can be destroyed, thus ensuring ultimate victory. The latter half of the year will be devoted to strengthening these fortifications in order that the offensive can be resumed at the earliest possible opportunity. These war preparations will be carried out as follows:

1. All war preparations will be carried out in the spirit of suicide attacks, and the total national power will be united into a fighting force that can furnish the necessary manpower for the coordinated war plans of the Army and Navy.

2. The main combat strength will be composed of air forces (including air special attack forces) and underwater and surface special attack forces. The greatest emphasis will be placed on the maximum development of their combat capabilities.

Relative to war preparations, other than those mentioned above, if they will not obstruct the build-up of the air forces and the special underwater and surface attack forces, priority will be given to important land defense forces, submarine forces, surface escort forces and supply forces in that order so that these forces, combined with the main forces, may meet the operational demands. In order to increase the air forces and the special underwater and surface attack forces to the size urgently required for these operations, it is expected that all other war preparations scheduled for completion prior to September will be postponed and those scheduled for completion after October will be temporarily suspended. Preparations for chemical warfare for both offen-

--ii--

sive and defensive operations will be effected promptly.

3. Relative to war preparations for intercepting the enemy at the center of our fortified region, all human and material strength will be mobilized so that they can be immediately and most effectively employed in action at the right moment. All possible steps will be taken to enable important combat forces to continue fighting with tenacity.

4. War preparations for the counteroffensive will be drawn up in a separate document.

B. Division of War Preparations

1. The first quarter of 1945 (from the beginning of April to the end of June):

a. The greatest emphasis will be placed on gaining control of the air and sea covering the area in which decisive action is being contemplated and especially on the destruction of enemy carrier task and occupation forces.

For this purpose emergency measures will be taken for the rapid build-up and employment of land-based air forces and special attack forces.

Preparations for offensive and defensive operations in the Homeland will be effected according to and in parallel with the foregoing program.

Specially designated surface forces will be ready by the end of June to conduct raiding operations on the sea near the Homeland. Steps will be taken to intensify the defense of industrial centers and commu-

--iii--

nications facilities against air attacks. Preparations for land combat on the Homeland will be carried out to the extent required by the war situation, provided that they do not obstruct other important war preparations of the Navy itself.

b. The protection to be given to surface traffic between Japan and Manchuria and China will be governed by the war preparations mentioned in the foregoing paragraph. Communications with the southern areas will be especially arranged so that they will be maintained even under the most serious combat situation. Sea transportation along the coasts of the Homeland will be so planned that it will be protected by land bases along the coast.

The surface-protecting forces will, for the time being, protect surface traffic between Japan and Manchuria and North China. Merchant vessels will be equipped with weapons which are adequate for antiaircraft and antisubmarine defense.

c. Most of the war materiel will be transported on suitable merchant vessels and the amount of supply will be kept to the minimum.

d. Preparations to frustrate the enemy's attempts to sever our short distance supply lines will be strengthened.

2. War preparations in the second quarter (from the beginning of July to the end of September):

a. An invincible structure will be established.

b. A portion of the preparations for counteroffensives will be carried out.

--iv--

c. Other war preparations will be the same as those prescribed for the first quarter.

d. Whether efforts are to be directed at preparations for war in the Homeland or at preparations for counteroffensives and sustained warfare will be decided according to the war situation in May.

3. War preparations in the third quarter (from the beginning of October to the end of December) and the fourth quarter (from the beginning of January to the end of March 1946):

War preparations prescribed for the second quarter will be continued and other programs for this period will be mapped out separately.

C. Urgent measures will be taken to procure important materials, especially for fuel and powder, so that a sufficient quantity can be rapidly supplied in Japan, Manchuria and China. The greatest emphasis will be placed on the securing of aircraft gasoline.

D. The Homeland will be organized so that production, training and war preparations can be carried out with the least possible amount of difficulty; the Homeland will be organized immediately into the front line with each area establishing a self-sustaining and self-defensive structure.

E. The overseas key areas will strive to establish self-sustaining and self-defensive structures.

II. Outline for the Execution of War Preparations

A. Aircraft with its Equipment and Facilities

--v--

efforts will be made to elevate the actual working efficiency of factory workers and to secure and expand aircraft production, while taking every possible measure to minimize damage from air raids. At the same time, the combat strength required as the main force of the Navy will be built up according to the following plant

a. Maximum emphasis in air preparations will be directed toward annihilation of enemy carrier task forces. A capable force will be maintained and strengthened as quickly as possible during the first quarter of preparations and thereafter the strength necessary for destroying other enemy objectives will be reorganized. For this purpose, importance will be attached to the preparation of fighter, reconnaissance and attack planes. In order to increase the effectiveness of the attack planes, principal emphasis will be placed on the over-all conversion of attack planes into special attack planes, the combined use of special attack planes and special type planes with acceleration of the production of large, extremely powerful aircraft.

b. Relative to aircraft for antiaircraft defense, fighting power will be increased by improving the performance of the aircraft now in use, by converting them into special attack planes and by accelerating production of special type planes. Relative to aircraft to be employed in attacking enemy invasion forces, plans will be drawn up to convert most of the aircraft used in training and those presently in storage into Special attack planes by late April. At the same time, efforts will be made to accelerate production of small special attack

--vi--

planes and conversion of other aircraft into small, special attack planes as soon as possible. With reference to escort aircraft for sea communications, these will be replenished with second-line planes, in addition to the planes being used exclusively for this purpose. Relative to aircraft for attacking enemy air bases, they will be maintained and strengthened as long as such aircraft are available.

2. The number of aircraft to be produced: Standard aircraft will be maintained and strengthened according te Chart 1. Special planes will be maintained and strengthened in accordance with the following section on Special Attack Planes.

3. Equipment and facilities relative to aircraft:

a. Antiaircraft defense measures for aircraft production facilities (including important related production facilities) will be completed quickly and thereafter intensified. Underground aircraft production facilities, capable of producing 1,200 frontline planes monthly (including special planes), will be completed during the first quarter of preparations.

b. Air bases will be prepared and strengthened in the following general order: Kyushu Area bases to be used for the coming decisive battle, Kanto Area bases for launching attacks on enemy carrier task forces, bases for use by special attack planes of the training air group and rear echelon bases in the Sanin, Korea and Hokkaido areas.

c. In addition to strengthening the radar network for air operations (including air defense), and the air defense for communica-

--vii--

Chart 1-a

Production of Aircraft for the First Half of Fiscal Year 1945

Naval Aircraft

Type of Aircraft

Minimum Requirement (The majority will be produced at dispersed underground factories The minimum requirements must be met at all costs)

Ultimate Goal

Remarks

Fighters

Shiden, Improved Model

2,400

2,400

Zero Fighter

1,800

2,700

To be converted into Shiden, Improved Model, as soon as possible

Raiden, Improved Model

600

Saiun

300

300

Ginga

100

100

Total

4,600

6,100

Recon Plane

Saiun

850

850

Bomber and Attack Planes

Ginga

700

700

Ryusei

300

300

Renzan

56

100

Total

1,050

1,100

Chart 1-b

Production of aircraft for the First Half of Fiscal Year 1945

(Cont'd)

Naval aircraft

Type of Aircraft

Minimum Requirement (The majority will be produced at dispersed underground factories. The minimum requirements must be met at all costs)

Ultimate Goal

Remarks

Patrol Planes

Type 1 Land Attack Planes

240

250

Scheduled to be employed as attack planes

Tokai

250

Total

240

500

Recon Seaplanes

Seiran

80

Transport Planes

Type Zero and Type I Transport Planes

320

Training Planes

Medium Land-based Training Planes

200

Utility Trainer

200

Type Zero Training Fighters

350

Type 99 Training Bombers

100

Training Planes Tokai

200

Total

1,050

Grand Total

6,740

10,000

ions, supply and repair facilities, everything will be done to improve these defense facilities in order to minimize damage from air attacks and maintain secrecy of preparations.

d. Weapons for air operations will be readied in sufficient quantity to maintain the air potential.

e. Additional details will be discussed in other sections, 4. Readying a carrier-based air force: Some of the already completed aircraft carriers are slated to be manned by special attack forces in the middle of 1945 and details will be discussed elsewhere.

B. Special Attack Craft and Related Facilities

1. Special attack craft will be readied in accordance with Chart 2. Special emphasis will be placed on the special underwater attack force, which will be the main strength in the annihilation of the enemy's invasion force and in the interception of his short-range supply lines. Also it will be the training force to be used against the enemy carrier task force. If necessary, details for preparations will be discussed elsewhere.

2. Related Facilities.

a. Production facilities will be dispersed and moved underground as promptly as possible and production will be greatly increased.

b. Various base facilities will be completed within the first quarter and strengthened thereafter. Additional details will be discussed separately.

C. Ships

--viii--

Chart 2-a

Special Attack Craft

Period

First Quarter From April to June 1945

Second Quarter

From July to September 1945

Third Quarter

From Oct 1945 to End of Mar 1946

Remarks

Classification

Special-type Aircraft

2,000

To be determined by a later conference

To be replenished with Suisei, Tenzan, Ki-115 and others. The details will be determined by a special conference.

Oka Plane

900

900

"

A special conference will be held to discuss improvement of performance

Kikka Plane

300

"

Shusui Plane

450

750

"

To be constructed through cooperation between the Army and Navy. Approximately one-third of this number will be constructed by the Navy.

Karyu Plane

5

"

Kaiten Human Torpedo

300

360

300

Chart 2-b

Special Attack Craft

(Cont'd)

Period

First Quarter

From April to June 1945

Second Quarter

From July to September 1945

Third Quarter

From Oct 1945 to end of March 1946

Remarks

Classification

Kairyu Midget Submarines

350

550

1,000

To be constructed by advancing the deadline as much as possible. Improvement in the performance of the Kairyu will be considered in the last half of the fiscal year

Koryu Midget Submarines

110

430

1,000

Small Submarines

40

120

Of the submarines scheduled for the first half, 40 will be readied by August. They will be equipped to recharge while cruising underwater as soon as possible

Shinyou

No. of Vessels

1,680

1,800

1,200

Engines

2,250

2,250

1,300

Notes

The number scheduled for the Third Quarter and thereafter is an approximate figure.

The details shall be determined by a later conference.

1. Ships will be readied in accordance with Chart 3. All ships will be made as compact as possible and whenever possible small ships will be used.

2. Armament

a. Armament will be conducted strictly in accordance with the priority system. At the same time, ships capable of carrying special attack planes will, if possible, be fitted for this purpose.

b. Every effort will be made to simplify the fitting out of vessels. At the same time, coast defense ships, starting with those to be newly constructed, will be equipped, if at all possible, with a mixed firing boiler in order to shorten the construction time. Above all, the construction period for antisubmarine craft and submarines will be drastically reduced and the submarines will be fitted so that they may recharge their batteries while cruising underwater.

c. Details will be discussed elsewhere.

3. Air defense measures will be taken to protect the construction of ships as well as ships already constructed.

D. Weapons (Excluding weapons employed in aerial combat). Weapons will be readied in accordance with Chart 4.

E. Surface Defense

Defense of communications between Japan, Manchuria and China

and, especially, defense of the seas adjacent to the Homeland, the Tsushima Straits, the Japan Sea and North China, will be stressed. Harbor and bay facilities, air bases, communications facilities, defense

--ix--

Chart 3-a

Ship Construction

Priority

Type of Ships

Requirement

Notes

4

Aircraft Carriers

2

Work will be suspended temporarily after the launching. Their use will be determined separately. Work on the "Ibuki" and "Kasagi" sill be suspended temporarily.

4

Otsu

1

Work will be suspended temporarily.

2

Destroyers

Tei

20

Six will be completely equipped in the first quarter of the fiscal year. Construction of the others will be started according to the situation. Loading of Kaiten will be made possible.

3

Submarines

Tei

2

Tei 2 (Bo)

5

In unavoidable cases torpedo-tubes will be equipped later.

2

High speed

16

2

Special type

2

Construction of ship No 5236 will be abandoned.

2

Supply

1

1

Escort-ships

Ko

30

Twenty will be completely equipped in the first half of the fiscal year. Construction of the others will be started according to the situation.

Hei

Tei

Chart 3-b

Ship Construction

(Cont'd)

Priority

Type of Ships

Requirement

Notes

3

Transports

First-class

5

Second-class

10

Small Patrol Boats

40

To be completed by July.

1

Ko

40

Auxiliary Escorts

Otsu

80

2

Light Minelayers

2

2

Converted Minelayers

6

To be completed by the end of June. (Four of them will be reconverted merchant ships.)

5

Special Landing Barges

460

200 will be made of iron and 200 of wood. 30 will be for amphibious purposes.

Remarks: If obstacles arise in the construction and equipping of the special attack craft, the date of completion for those expected to be completed by September will be extended, while those expected to be finished after September will be temporarily suspended.

Chart 4-a

Weapons

1. Antiaircraft Weapons

Classification of Weapons

Quantity

No. of Shells per gun or Projector

Remarks

AA Gun

Type-1 127mm gun

30

500

Armour piercing shells will be about 10% of land based AA Guns' shell.

127mm gun

100

500

120mm gun

470

400

Type 98 100 mm gun

50

500

Total

650

Large Calibre Machine Gun

40mm machine gun

500

4,000

1. Land based machine guns will be of vehicle types.

2. Armour piercing shells will be about 20% of all machine gun shells.

25mm machine gun

10,000

3,500

Including 2880 guns scheduled for delivery to the Army

13mm machine gun

1,200

4,000

Balloon, Kite

AA balloon

150

AA kite

1,600

Searchlight

150

Chart 4-b

Weapons

2. Land Combat Weapons

Classification of Weapons

Quantity

No. of Shells Per Gun or Projector

Remarks

Rocket Gun

200mm rocket gun

1,200

50

120mm rocket gun

4,000

50

ROTA gun

17,500

4

Bomb Launcher

For 250 kilo bomb

10,000

For 60 kilo bomb

20,000

Quick Firing Gun

Medium and Small calibre gun

200

300

Guns will be converted from shipboard guns

Large calibre gun

12

300

200mm short barrel gun

50

60

120mm short barrel gun

850

400

80mm gun

50

400

Others

80mm mortar

10,000

300

7.7mm machine gun

2,000

4,000

Rifle

100,000

300

Pistol

12,000

60

Grenade thrower

2,500

100

Small mine

150,000

Chart 4-c

Weapons

Classification of Weapons

Quantity

No. of Shells Per Gun or Projector

Remarks

Others

Attack mine

100,000

Stick mine i

150,000

Hand grenade (corn-shape)

100,000

Hand grenade

5,000,000

Molotov cocktail bomb

150,000

Incendiary grenade

60,000

Dynamite

100,000

Smoke bomb

60,000

Small smoke bomb

150,000

Steel helmet

1,000,000

Sword

300,000

Others

Secondary small arms necessary for the above mentioned weapons will be prepared.

Simple hand weapons will be decided later

Chemical Weapons

Gas mask

1,000,000

Light anti-gas suit

300,000

Anti gas cover

300,000

Neutralizer

Powder No 3

600 tons

Powder No 4

2,500 sets

Powder No 5

2,500 sets

Others

Secondary small arms necessary for the above mentioned weapons will be prepared. Preparation for positive chemical warfare will be decided separately

Chart 4-d

Weapons

Classification of Weapons

Quantity

No. of Shells Per Gun or Projector

Remarks

Smoke

Screen

Weapons

Smoke powder

3,000 tons

40 kilogram smoke screen apparatus

3,000 sets

Gunpowder

25,000 tons

Explosive

20,000 tons

Vehicles

Amphibious tank

70

Tractor

70

Other vehicles

To be decided later

3. Anti-submarine Apparatus [Split table here.]

Classification

Quantity

Remark

Depth Charge

40,000

Mine

30,000

Hydrophone, Magnetic Detection Apparatus

Necessary amount for the anti-submarine vessels and airplanes

4. Other Weapons

Necessary amount for vessels, planes and other strength will be prepared.

facilities, patrol facilities and repair facilities, which are necessary for antisubmarine and antiaircraft defense, will be readied and strengthened.

As for the defense of the Southern Area communications routes, every effort will be made to preserve and strengthen the coastal shipping lanes along the continent.

F. Defense of the Areas.

1. The defense priority for the various areas will be as follows:

a. Homeland, Ryukyu Islands, Bonin Islands and South Korea.

b. Central and North China, and North Korea.

c. Other areas.

2. Outline of Defense:

a. The Homeland, South Korea Area, Ryukyu and Bonin Islands sector:

(1) Defense of the Homeland area will be carried out under the plan that the Kanto, Kyushu, South Korean and Hokkaido areas will be major fortresses linked with each other by intermediate fortifications and that control will be maintained over the Tsushima, Tsugaru, and Soya Straits and the southwestern channels of the Homeland. As for defense of the Ryukyu and Bonin Islands, the existing program will be strengthened in order to covert them into truly impregnable strongholds.

Above all, special efforts will be directed toward completion of the facilities necessary for displaying the combat effi-

--x--

ciency of the air forces and the special attack forces, which are to be used in the decisive battle, and toward perfection of communications facilities of every kind.

These defenses will be completed generally by the end of the first quarter and quickly strengthened during and after the second quarter.

(2) More thorough measures will be taken to strengthen antiaircraft defenses. These measures, which have already been discussed will be speedily completed so that the vital sources of the nation's fighting power, as well as vital supply stockpiles, may be developed to the maximum and so that various production capacities may be maintained at peak level on a long range basis.

(3) A strong and effective supply line, combining sea, land, and air routes, will be established.

b. Central China, North China, and Korea: Relative to defenses in Central China, North China and Korea, emphasis will be placed on disruption of enemy operations aimed at cutting off our Homeland from the continent. This operation generally will be conducted in accordance with the foregoing paragraph.

c. Other areas: Local defense facilities will be used and every effort will be made to strengthen these defenses.

G. Fuel and Powder "RO"

1. Fuel: The production goal for the principal fuels shall be as shown in the following table:

--xi--

First Quarter

Second Quarter

Homeland

Southern Area

Total

Homeland

Southern Area

Total

Aviation Fuel (kiloliters)

130,000

60,000

190,000

140,000

70,000

210,000

Heavy Oil (tons)

120,000

160,000

280,000

130,000

150,000

280,000

Ordinary Gasoline (kiloliters)

9,000

10,000

27,000

9,000

10,000

46,000

Light Oil (kiloliters)

8,000

27,000

2. Powder "RO" Ten thousand tons. This amount represents the total Army and Navy requirements.

--xii--