Operational Plans of the Japanese Navy against the United
States, Great Britain, the Netherlands and China
Developments Leading to the Formation of Attack Plans
Events leading to the decision to wage war against the United States, Great Britain and the Netherlands were discussed in Monograph 150, Political Strategy Prior to Outbreak of War, Part IV. As the plan for the Hawaii Operation was especially important, further details of the circumstances which caused the decision to carry out this operation to be made are given her under.
In the middle of September, operations in the Hawaii area were studied through secret war games by a restricted group of officers. The conclusion reached was that there was an even chance that the main forces of the United States Fleet would be at anchor in Hawaiian waters and present a good opportunity for attack. However, should the American Fleet be sufficiently alert, it might be necessary to break through enemy opposition. On the other hand, there was a possibility that the sea area north of Hawaii might not be effectively patrolled and it appeared that the best move would be to approach through that area. Should the surprise attack succeed, it was estimated that about two-thirds of the American capital ships at anchor in Hawaii would be sunk, and Japanese losses probably would be two or three aircraft carriers.
Three problems had to be faced in carrying out the Hawaii operation:
1. How could we approach through the enemy patrol network and effect a surprise attack?
2. How could supplies be guaranteed while an advance was being made on Hawaii (for approximately 12 days) with unpredictable and difficult weather conditions to contend with?
3. How could we foretell whether the United States Fleet would be lying at anchor in Hawaii or maneuvering at sea, even if we were fortunate enough to approach Hawaii without being detected?
In addition to the above problems, there were technical difficulties which had to be considered in executing the attack. Among those were the following:
1. Japan had no air torpedo at that time which could be used in the shallow waters of Pearl Harbor.
2. Japan did not have heavy armor-piercing bombs for sinking capital ships.
No clear-cut course of action, therefore, was arrived at at the conclusion of the war games, and the Navy General Staff and the Combined Fleet decided to study the problems further.
The plan for attacking the bulk of the United States Fleet in Hawaiian waters at the beginning of hostilities had long been an idea of the Japanese Navy. The plan, however, had been based on the employ-
ment of submarines to watch the entrance of Pearl Harbor and attack principal American ships entering and clearing the harbor, or to sink such ships in the channel at the harbor's mouth, and, thus, temporarily, seal the harbor. The development of aircraft carriers gave birth to the idea of using planes for a surprise attack. Commander in Chief of the Combined Fleet, Admiral Isoroku Yamamoto, saw the advantages of a large-scale air assault, and, in January 1941, instructed his staff to study the idea. Little progress was made and the research was conducted so secretly that only those actually concerned knew anything about it.
The Navy General Staff clung to the Interception Operation, which had been developed over long years of research. This plan called for the use of submarines in the Hawaiian area to watch and conduct surprise attacks on United States ships, but the use of planes was not contemplated. Consequently, the operations plan against the United States for the year 1941, which was decided in April 1941, did not include air attacks on the Hawaiian area.
After August, with the situation daily becoming more critical, the Combined Fleet, too, began to conduct more thorough research in regard to the details of operations and the Commander in Chief presented his plan concerning the Hawaii Operation officially for the first time to the Navy General Staff. At that time, the Navy General Staff was deeply concerned in regard to the air strength vitally necessary for the Southern Operations, and, since negotiations with
the Army regarding the use of the Army Air Force in the operation were not then under way, the Navy General Staff was not willing to divert the naval air strength which they felt indispensable to the Southern Operations, to such a bold and risky operation as a surprise air attack on Hawaii, which would require nearly the entire carrier strength. However, after the war games hold early in September, various technical problems were solved and the Army complied with the Navy's request to transfer from Manchuria sizable air strength for support of the Malaya Operations, in accordance with an operational agreement with the Army General Staff. The Navy was thus assured of a 3 to 1 air force ratio in their favor in the Philippines and Malaya Operations. As, under the circumstances, they did not then need to commit as many aircraft carriers to support the landing operations, the Navy General Staff then approved the Hawaii Operation plan of the Combined Fleet, but did not agree to the strength the Combined Fleet considered necessary for the operation.
On 20 October, the Navy General Staff decided informally upon an operations plan for the Navy and informal instructions were issued to the Combined Fleet on 29 October. These instructions contained a paragraph directing an air attack against the United States Fleet in the Hawaiian area at the beginning of the war but no mention was made of the air strength to be allotted to the operation. It was felt that it was not possible to allocate definite strength to the Hawaiian area as the United States and Great Britain were reinforcing their
air forces in strategic key points throughout the Southern area and also that further reinforcement of the air forces for the prosecution of the Southern Operation might be necessary.
At the same time, it was pointed out that as the Navy land based air force on Formosa had been reinforced considerably and its fighter units could escort bomber units in mass dawn attacks against Manila, there would be no need to commit carrier fighters for the initial air attacks against the Philippines.
Early in November, Imperial General Headquarters and the Government decided to open hostilities at the beginning of December. On
3 November, Commander in Chief of the Combined Fleet Yamamoto came to Tokyo, and, at that time, Chief of the Navy General Staff Nagano while issuing instructions on the operational plan against the United States, Great Britain, the Netherlands and China, gave Yamamoto approval and directions for the use of the entire available fast carrier strength (six carriers) in a surprise air attack on the American Fleet in the Hawaii area.
Circumstances Leading to the Decision to Use Midget Submarines in the Hawaiian Area
Originally, midget submarines were designed to be used in decisive battles on the open sea. They were to be taken aboard submarine tenders. (The Chiyoda was the only submarine tender then in existence.) They were to slide down the stern of tenders in large numbers and be launched like torpedoes against the enemy fleet at close quarters.
The study and testing of this weapon was started in 1940 in the utmost secrecy and there were some fifteen or sixteen of these submarines at the time the war began.
The idea of using midget submarines (at the time for security reasons called "Ko Target") against the United States Fleet in Pearl Harbor simultaneously with the opening of hostilities, originated among the young naval officers about August 1941 when midget submarine training forces began studying methods of attacking ships in a harbor.
In early October, a staff officer of Imperial General Headquarters proposed the use of these submarines in opening hostilities in Pearl Harbor. The plan was to carry these midget submarines on the deck of standard submarines and, upon approaching the entrance of the enemy harbor, the standard submarines would release them while submerged, thus allowing them to sneak into the harbor.
Plan of Operations of Imperial General Headquarters, Navy Section
In accordance with the Imperial Conference's decision of 5 November that "war preparations should be completed by the beginning of December," Imperial General Headquarters issued, the same day, the following Navy orders and directives to the Commander in Chief, Combined Fleet:
Imperial General Headquarters Navy Order No 1
5 November 1941
To: Yamamoto, C in C, Combined Fleet
1. In view of the great possibility of being compelled to go to war against the United States, Great Britain and the Netherlands in the cause of self-existence and self-defense, Japan has decided to complete various operational preparations within the first ten days of December.
2. The Commander in Chief of the Combined Fleet will make the necessary operational preparations.
3. The details of the operation shall be directed by the Chief of the Naval General Staff.
By Imperial Order
Chief of the Naval General Staff
Imperial General Headquarters Navy Order No 2, addressed to Koga, Commander in Chief, China Area Fleet, and Imperial General Headquarters Navy Order No 3 addressed to Toyoda, Commandant, Kure Naval District, Sumiyama, Commandant, Sasebo Naval District, Hirata, Commandant, Yokosuka Naval District, Kobayashi, Commandant, Maizuru Naval District, Sakamoto, Commandant, Chinkai Naval Minor District, Yamamoto, Commandant, Mako Naval Minor District, Okuma, Commandant, Ominato Naval Minor District and Ukita, Commandant, Port Arthur Naval Minor District, were similar in text to Imperial General Headquarters Navy Order No 1.
Imperial General Headquarters Navy Directive No 1 
To: Yamamoto, C in C, Combined Fleet
1. The Combined Fleet will advance the necessary forces at a suitable time to a preparatory point prior to commencement of hostilities to stand by in the event of unavoidable hostilities against United States, Great Britain and the Netherlands, in the first ten days of December.
2. During the above-mentioned advance, strict watch will be kept against unexpected attacks.
3. The operational policy against United States, Great Britain and the Netherlands is shown in a separate volume.
Chief of the Naval General Staff
Imperial General Headquarters Navy Directive No 2 contained similar orders to Koga, Commander in Chief, China Area Fleet.
Imperial General Headquarters Navy Directive No 3
3 November 1941
Toyoda, Commandant, Kure Naval District,
Sumiyama, Commandant, Sasebo Naval District
Hirata, Commandant, Yokosuka Naval District
Kobayashi, Commandant, Maizuru Naval District
Sakamoto, Commandant, Chinkai Naval Guard District
Yamamoto, Commandant, Mako Naval Guard District
Okums, Commandant, Ominato Naval Guard District
Ukita, Commandant, Port Arthur Naval Guard District
. Imperial General Headquarters Navy Directives were compiled from memory by Rear Admiral Tomicka, Sadatoshi, Chief of the Operations Section, Naval General Staff at the time these orders were issued. They are believed to be practically identical with the original directives.
1. Each commandant of the naval districts will carry out defense according to the outline of the Imperial Navy Defense Plan for 1941, in order to be prepared in the event of unavoidable hostilities against United States, Great Britain and the Netherlands in the first ten days of December.
2. Each commandant of the naval districts and the naval guard districts will keep strict watch against unexpected attacks by the United States, British or Dutch forces and, at the same time, cooperate with the guard of the Combined Fleet.
Chief of the Naval General Staff
The gist of the Imperial Navy Operational Policy, mentioned in Imperial General Headquarters Directive No 1, was as follows:
Imperial Navy Operational Policy in Case of War Against the United States, Britain and the Netherlands
Outline of Operational Policy
Control over the China Coast and the Yangtze River basin will be maintained, the enemy fleet and air power in the Orient will be destroyed and, at the same time, key areas in the Southern area will be occupied, thereby establishing a position capable of withstanding enemy attacks indefinitely.
Should the enemy fleet attempt an invasion during these periods, it will be intercepted and destroyed, thereby breaking the enemy's will to fight.
Combined Fleet's Operational Policy
First Phase Operation
1. A force formed around the 2d and 3d Fleets, the Southern Expeditionary Fleet and the 11th Air Fleet, will destroy enemy surface and air forces located in and around the Philippines, British Malaya and the Dutch East Indies, and also give the Army cooperation in its operations.
a. After taking the initiative in air attacks against the enemy air forces and fleets in the Philippines and Malaya, advanced army groups will be landed in these areas
and establish advance bases. Then the main invasion force will land and secure these areas.
b. British Borneo will be occupied in the initial stage of the operations, and then Dutch Borneo, Celebes, and southern Sumatra as soon as possible. Key points in the Moluccas and Timor will be occupied at the first opportunity and air bases established. These air bases will be utilized first to secure command of the air over Java and then to invade the island.
c. Key areas of north Sumatra will be occupied after the capture of Singapore. The Burma operations will be begun at an appropriate time and the supply route to China cut.
2. Force formed around the 4th Fleet
This force will be responsible for the defense and control of the South Sea Islands area and will maintain sea communications. The force will capture Wake and attack and smash enemy advanced bases in the southern Pacific area. It will cooperate with the Army in the invasion of Guam and then invade key points of the Bismarck Archipelago at an opportune time.
3. Force formed around the 5th Fleet
This force will be responsible for the patrol of Japan's eastern sea area, for the protection of sea communications in that area, for security against attack from the Aleutian area and for defense of the Bonin Islands and, at the same time, for maintaining security against Soviet attacks.
4. Force formed around the 6th Fleet
This force will be responsible for reconnoitering, watching and surprise attacking Hawaii and the west coast of the United States and for destroying the enemy line of sea communications.
5. Force formed around the 1st Air Fleet
This force will attack Hawaii and thereafter will render support chiefly to the operations of the 4th Fleet and to the southern invasion operations.
6. Main force of the Combined Fleet
This force will take appropriate action to support all operations.
7. An element of the Combined Fleet
This element will be responsible for destroying enemy surface traffic in the Pacific and the Indian Ocean areas.
Second Phase Operation
1. Force formed around the 1st and 11th Air Fleets
This force will be responsible for searching for and attacking enemy forces and for attacking and destroying advanced enemy bases.
2. Third Fleet, Southern Expeditionary Fleet and other forces, as necessary.
This force will be responsible for the security of occupied areas and will also attack and destroy advance enemy bases along our perimeter.
3. Force formed around the 4th Fleet
This force will seize and secure the South Seas area and the Bismarck Archipelago, maintain our line of sea communications and attack and destroy advance enemy bases along our perimeter. It will also seek and attack invading enemy fleets.
4. Force formed around the 5th Fleet
This force will defend the Bonin Islands, patrol the seas to the east of Japan and north of the Bonin Islands and maintain our line of sea communications. It will also seek and attack invading enemy fleets.
5. An element of the Combined Fleet
This element will be responsible for the destruction of the enemy line of sea communications in the Pacific and Indian Oceans.
6. Main force of the Combined Fleet
This force will take appropriate action to support all operations.
7. When the United States Fleet attacks, the 6th Fleet will maintain contact with the enemy. Base Air forces and submarine forces will attack the enemy first and, at the proper time, the main force of the Combined Fleet will muster its full force in interception and destroy the enemy.
8. When the British Fleet attacks, the 3d and 4th Fleets, the Southern Expeditionary Fleet and air and submarine forces will establish contact with the enemy and reduce the fleet. The main force of the Combined Fleet, depending upon the condition and location of the United States Fleet, will engage and destroy the British Fleet, at the appropriate time.
9. Key points to be defended
(Those marked "o" are advanced bases.)
Manila (o) Hongkong Davao Singapore (o) Batavia Soerabaja (o) Tarakan Balikpapan Menado Makasar Ambon Penan Rabaul
Operational Policy for the China Area Fleet
This fleet will be responsible for the capture of Hongkong in addition to other tasks assigned separately.
The gist of the Central Agreement between the Army and Navy concerning Southern Operations concluded at Tokyo on 12 November 1941 was as follows:
Destruction of principal bases of the United States, Britain and the Netherlands in East Asia, and the occupation and security of strategic areas in the south.
Areas to be occupied: Philippines, Guam, Hongkong, British Malaya, Burma, Bismarcks, Java, Sumatra, Borneo, Celebes and Timor.
1. Commence operations simultaneously with a surprise attack on the Philippines and Malaya and complete operations in the shortest period possible. Commence operations with a surprise landing of the Malaya Advance Group and surprise air raids on Malaya, and the Philippines. Exploit the success of these air raids and invade the Philippines and Malaya with the main force of the Occupation Group.
2. Occupy Guam, Hongkong and important areas in British Borneo and pacify Thailand and French Indo-China during the initial stage of the operations.
3. Occupy important areas of southern Sumatra as operations in the Bismarcks, Dutch Borneo, important areas in Celebes, and Malaya progress, and prepare for the Java Operation.
4. Occupy key areas of the Moluccas and Timor during this period or as soon as the above operation is finished.
5. Invade Java after gaining control of the air and occupy North Sumatra after Singapore is occupied.
6. Although the disposition of the Combined Fleet may be revised because of the movements of the main United States forces, or if war with Soviet Russia begins, the Philippines and Malaya Operations will proceed without interruption.
7. Enemy air bases in southern Burma will be captured and, after the operation is generally completed, the conquest of Burma will be begun.
8. Enemy opposition will be anticipated during landing operations.
9. If British forces enter southern Thailand while we are still preparing for this operation, elements of the armed forces will advance without delay to Thailand by land and sea and secure Bangkok. They will also secure air bases in the south. The prearranged plan will be followed if a British invasion of Thailand begins after the Advanced Group has departed from its assembly point. If, before departure, landing of the main body is delayed, a landing will be made in force after intensifying air operations. This will be done by transferring part of the naval air forces from the Philippines area.
10. If the British or American forces launch attacks while we are still preparing for the operation, they will be intercepted with the force available in and around the area under attack and an air offensive will be launched against the pertinent armies.
Other moves will support those outlined above.
Forces to be Employed
Philippines: The 14th Army (16 Division, 48th Division, 2 tank regiments, 44 AA artillery batteries and 6 army artillery battalions).
Thailand and Burma: The 15th Army (33d and 55th Divisions).
Netherland East Indies: The 16th Army ((2d Division, (38th Division), (48th Division), 56th Mixed Infantry Group, 3 tank regiments, 88 AA artillery batteries and 5 army artillery battalions)).
Malaya: The 25th Army (Guards Division, 5th Division, 18th Division, 4 tank regiments, 11 army artillery battalions and 60 AA artillery batteries).
Forces under direct control of the Southern Army: The 21st Division, 21st Brigade, 3d Air Brigade, 5th Air Brigade, 21st Air Regiment, and 48 AA artillery batteries.
The 23d Army
Hongkong: The 38th Division and 1 air regiment.
South Seas Detachment
Pacific Islands: The 55th Mixed Infantry Group.
Note: Forces in brackets represent those available for dual employment.
(Note: This was an agreement in regard to the outline of disposition of forces. Consequently, there were some changes in actual operations, and matters dealing with purely naval operations were not included in the agreement.)
The 4th and 5th Submarine Squadrons (South Pacific).
The 11th Air Fleet (Philippines and Netherlands East Indies). An element of the 3d Battleship Division and the 3d Destroyer Squadron of the 1st Fleet (Malaya). An element of the 3d Carrier Division, element of the 1st Destroyer Squadron and the 6th Cruiser Division* (Philippine and Netherlands East Indies.)
The 2d Fleet (initially the main body will be in the Philippines and an element in Malaya, later an element will reinforce the Malay Unit and the mayor force will be sent to the Netherlands East Indies). (The 4th, 5th and 7th Cruiser Divisions, the 2d and 4th Destroyer Squadrons, and the 8th Cruiser Division.*)
The 3d Fleet (the main body will be in the Philippines with one element in Malay, and later in the Netherlands East Indies). (The 16th Cruiser Division and 17th Minelayer Division, the 12th Seaplane Tender Division, and the 1st and 2d Base Force.)
The 4th Fleet (Pacific Islands). (Elements of the 18th Minelayer Division, an element of the 6th Destroyer Squadron, Base Forces, the 24th Air Flotilla, and one converted aircraft carrier.)
The Southern Expeditionary Fleet (Malaya, British Borneo, and Sumatra,) (The Kashii, Shumushu, and other destroyers, one aircraft carrier, and two seaplane tenders.)
The China Area Fleet:
The 2d China Expeditionary Fleet (Hongkong). (The greater part of the 2d China Expeditionary Fleet, an element of the China Area Fleet, and an element of the Combined Fleet.)
(Note: * indicates elements that will be employed when needed.)
Commencement of Operations
The date for the execution of operations (X-day) will be fixed by Imperial order.
Surprise landing on Malaya on X day (an initial air raid will be made, if necessary, depending upon the situation) and air raids on the Philippines to acquire the initiative. In case of bad weather, a surprise landing on Malaya will be made, if at all possible, and the landing of advance unite on the Philippines will be postponed.
The attack on Hongkong will be opened after the landing and air raids on Malaya are confirmed, and that on Guam will be conducted after the first air assault on the United States Fleet in Hawaii is verified.
In case the enemy initiates a serious attack before X day, a counterattack will be launched provided an Imperial order for commencing operations has been issued.  Action will have to be withheld until an Imperial order has been issued.
Essentials of Operations
1. Philippines Operations
a. Army and Navy Air Forces will execute air attacks from Formosa and Palau and a naval forces will raid Batan Island and establish an emergency landing field shore.
b. Advance units
On X-1 day these units will depart from their places of assembly and will land on Aparri, Vigan (and then Laoag), Legaspi, and Davao. Jolo Island will be occupied as quickly as possible and will be guarded by naval units.
c. By X+14 day the main body of the 14th Army will land at Lingayen and the remainder will land at on Lamon Bay. They will then advance and attack Manila. (The nucleus of the 3d Fleet will escort this force.)
d. After the landing of the main body of the Army, one mixed brigade will conduct mopping-up operations on Luzon Island. The 48th Division will assemble in Manila. This division will be used in the Netherlands East Indies invasion force.
 Imperial General Headquarters Navy Order No 5, 21 November 1941, gave this authority to the C in C, Combined Fleet.
2. Malaya Operations
a. The 25th Army, the 3d Air Brigade, and the Southern Expeditionary Fleet.
The Advance Force will conduct surprise landings at Bandon, Nakhon, Singora, and Pattani and maintain bases there. Army and Navy Air Forces will launch initial air attacks from the southern part of French Indo-China in order to destroy the enemy air force and surface vessels.
Plan B (In case it is not possible to launch the surprise landings.)
The landing of advance elements will be effected in the form of surprise landings by small groups. (Launched from the west coast of Indo-China.) The main body of the Advance Force will start landing one day after X day.
Imperial General Headquarters will decide if Plan B is to be adopted before the Advance Force departs from its place of assembly.
b. After the landing of the Advance Force, another unit will land at Kota Bharu as rapidly as the situation permits. (Depending on the situation, a small group may land at Kota Bharu at the same time as the main body of the Advance Force begins landing.)
c. After some of the escort vessels of the 14th Army return, the main body of the 25th Army will gradually land in South Thailand and then proceed to Singapore. At an opportune time, one corps will attempt a landing on the eastern coast of Malay.
3. British Borneo Operations
At the outset, an element of the forces under the direct command of the Southern Army will make a surprise attack at Miri and will then advance and occupy Kuching. Bases will be maintained so as to facilitate the Navy Air Force advance.
4. Hongkong Operations
One group of the 23d Army and the nucleus of the 2d China Expeditionary Fleet will destroy enemy vessels in the area, and, after breaking through enemy positions on Kowloon Peninsula, will invade Hongkong. After the capitulation of Hongkong, this group will assemble for the invasion of the Netherlands East Indies.
5. Guam and Bismarck Operations
The South Seas Detachment and the force formed around the 4th Fleet will invade Guam, and after passing over the guard duty to a Navy landing force, these forces will then occupy Rabaul. There they will again be relieved of guard duty by another landing force.
Following this, the South Sea Detachment will advance to Palau.
6. Netherlands East Indies Operations
Elements of the 16th Army will occupy Tarakan, Balikpapan, Bandjermasin, Ambon, and Keopang (naval units will relieve the troops guarding Tarakan and Ambon).
Navy forces will occupy Menado, Kendari, and Makassar and elements of the 16th Army will occupy key positions on Bangka Island and Palembang.
Next, the main body of the 16th Army will land in the vicinity of Batavia and the remainder will land near Soerabaja. These two forces will eventually occupy Batavia, Bandoeng, and Soerabaja. Elements of the 25th Army will land on Medan from the western coast of Malay and occupy Atjeh and then Sabang.
7. Thailand and Burma Operations
Elements of the 15th Army will proceed from southern French Indo-China to south Thailand and an element will advance to Victoria Point. One group, constituting the main body of the 15th Army, will advance to Bangkok overland from French Indo-China. Another group will advance from North China to the vicinity of Bangkok about 40 days after X day.
On arrival, the main body of the 15th Army and elements of the 15th Army will occupy bases in Moulmein.
Matters Concerning Command
The Army and Navy will execute joint operations. Local land operations will be performed under a unified command according to the situation.
Air operations will be conducted in accordance with the Central Agreement between the Army and Navy concerning the Southern Air Operations. (This will be mentioned later.)
Shipping and Communications Liaison
Refer to Central Agreement as per supplement.
Supply and Sanitation (Omitted)
Transportation and Escort
Assembly points of each invasion force will be as follows:
The Guam Invasion Force Bonin Islands The Philippines Invasion Force The advance unit for North Luzon Pescadores or Takao The advance unit for Davao and Legaspi Palau The main force for Lingayen Pescadores The main force for Lamon Bay Nansei Islands (Nakagusuku Bay) British Malay Invasion Force Advance forces The first group Hainan Island The second group Southern French Indo-China Main force: The first group Formosa and Canton The second group Hainan Island and Southern French Indo-China The British Borneo Invasion Force Camranh Bay
The Netherlands East Indies Invasion Force Element for Borneo and Moluccas Palau Element for Sumatra Hongkong Main forces for East Java Luzon Main force for West Java Formosa and Hongkong
Date and Hour of Operations and the Standard Time to be used
Calculation of dates will begin from the date of opening of operations (by Imperial order). The time to be used is the central standard time (Tokyo time).
Army and Navy Commanders to be responsible for local agreement
Army Navy C in C, Southern Army C in C, Combined Fleet and 2d Fleet C in C, Southern Army C in C, Southern Expeditionary Fleet Commander, 14th Army C in C, 3d Commander, 16th Army Fleet Commander, 15th Army C in C, Southern Expeditionary Commander, 25th Army Fleet Commander, 3d Air Brigade C in C, 11th Air Commander, 5th Air Brigade Fleet Commander, 3d Air Brigade C in C, Southern Expeditionary Fleet and Commander, 22d Air Flotilla Commander, South Seas C in C, 4th Fleet Detachment C in C, China Expedi- C in C, China Area Fleet tionary Army Commander, 23d Army C in C, 2d China Expeditionary Fleet
Designation of Operations
Entire Southern Area Operations A-Go Operations Philippine Operations M Operations Malay Operations E Operations Dutch Indies Operations H Operations Guam Operations G Operations
British Borneo Operations B Operations Hongkong Operations C Operations Bismarck Operations R Operations
Exchange of Intelligence and Others (Omitted)
Central Agreement Between Army and Navy for Southern Air Operations (decided in November 1941)
The plan is to first destroy the American and British Air Forces in East Asia, then the Dutch Air Force, and, at the same time, to cooperate with the invasion forces. Meanwhile the Navy Air Force will attack enemy vessels.
Forces to be Employed
1. Philippines Operations a. Navy The 11th Air Fleet Land reconnaissance planes 9 Fighters 108 Land medium bombers 144 Flying boats 18 Total: 279 In addition, about 60 seaplanes (about 40 planes at first) attached to the 3d Fleet will be employed.  Some small type aircraft and 20 fighters will be used for air defense on Formosa. b. Army  In the beginning the 3d Fleet had 40 seaplanes. Later, it was reinforced from the Homeland by one seaplane tender carrying 8 seaplanes. About the same time, 13 seaplanes were transferred to the 3d Fleet from the Southern Expeditionary Fleet.
The 5th Air Brigade Reconnaissance planes 36 Fighters 36 Light bombers 54 Heavy bombers 18 Total: 144 In addition, about 30 fighters will be employed for air defense in Formosa. 2. Malay, Burma and Borneo Operations a. Navy The 22d air Flotilla Land reconnaissance planes 9 Fighters 36 Land medium bombers 72 Total: 117 The Southern Expeditionary Fleet has about 7 seaplanes (at first, it had about 20).  b. Army The 3d Air Brigade Reconnaissance planes 72 Fighters 168 Light bombers 108 Heavy bombers 99 Total: 447 After the Philippines Operations are concluded, the 5th Air Brigade will be transferred to this area.  Thirteen seaplanes were transferred to the 3d Fleet to take part in the Philippines Operation.
3. Netherlands East Indies Operations
The mayor part of the force a engaged in the Philippines and Malay Operations will be transferred to this area, and, depending upon the situation, an element of the 1st Air Fleet may be employed, if necessary.
After completion of the Malay Operations or after Singapore comes under the control of the Japanese forges, as many planes as possible will be transferred from the Malay area.
4. Guam Operations
About 13 seaplanes of the 4th Fleet will be employed.
5. Bismarck Islands Operations
About 17 seaplanes of the 4th Fleet will be employed and, according to the situation, carrier-borne air force or base air force will be used.
Outline of Operations
1. The initial blow will be delivered against the American and British Air Forces. Simultaneous attacks against air forces stationed in the Philippines and Malay will be launched as soon as possible, but should the weather interfere with the action on X day, attacks will be made separately. The attacks will be started from Formosa, Palau and aircraft carriers.
2. Philippines Operations
Bases in the Formosa area:
Koshun, Taito, Kagi, Kwarenko and Taihoku (For joint use) Takao, Toko, Tainan, Taichu, Shinchiku and Mako (For Navy) Kato, Choshu, Heito, Hozan, Tainan and Taichu (For Army)
Formosa air defense:
Air defense of Mako Anchorage will be the Navy's responsibility and other places will be the Army's responsibility.
Assignment of offensive targets:
The Navy will be responsible for attacks on enemy air and surface forces. The Army will cooperate in destroying the enemy air force in the Luzon area.
Air cooperation for the Advance Unit's operations, and construction and use of air bases.
Appari, Laoag, and Vigan.............Army Air Force and a part of Navy Air Force Davao, Legaspi and Jolo..............Navy Air Force
Air cooperation to be given to operations of the main body of the 14th Army:
For Lingayen Bay Operation...........Army Air Force and a part of. Navy Air Force For Lamon Bay Operation..............Navy Air Force
After the termination of the Philippines air operation, the Navy Air Force will be transferred to the Netherlands Indies Operations and the Army Air Force will be transferred to the Malay Operations.
3. Guam and Bismarck Operations
The Navy will take sole responsibility for these operations.
4. Malay, Burma and British Borneo Operations
Bases to be used during the first phases:
Hoihow, Samah, Fatrow, Saigon, Nhatrang, and Tourane (For joint use)
Thudanmot, Soxtrang (Puck and Kompongtrash) (For Navy)
Pnompenh, Kompongtrash, Tani, Kompongchnang, Krakor, Siamreap and Puck (For Army)
Operational Responsibility (responsibility for the maintenance of bases,:
Malay - The Army Air Force will be primarily responsible and the Navy Air Force will cooperate. The operations against vessels will be left to the Navy Air Force.
Burma and Thailand - The army Air Force will be in charge of operations in these areas.
British Borneo - The Navy Air Force will be in charge of the operations in this area.
Singapore - the Navy Air Force will be in charge and the Army Air Force will participate in the attack, when possible.
Air cooperation in the Operations of the advance force:
Anchorages in Singora and Bandon are to be guarded by the Navy Air Force and other anchorages by the Army Air Force.
5. Hongkong Operations
Primarily an Army Air Force responsibility.
6. Netherlands East Indies Operations
Primarily an Navy Air Force responsibility.
North Sumatra - Primarily an Army Air Force responsibility.
South Sumatra and West Java- Joint responsibility of the Army and Navy Air Forces.
7. After the termination of the Philippines, Malay, and Netherlands East Indies Operations, the Navy Air Force will engage in operations against the United States and Australia, while the Army Air Force will be transferred to China and Manchuria.
Operational Plans of the Combined Fleet
In accordance with the operational policy of the Navy General Staff concerning the war against the United States, Britain, and the Netherlands, as already stated, the Combined Fleet on 5 November 1941 issued the following operational order simultaneously with the issuance of Imperial General Headquarters Navy Order No 1 and Imperial General Headquarters Navy Directive No 1, causing all the units under
its command to prepare operational plans to execute their respective missions. At the same time, the Combined Fleet, in accordance with Imperial General Headquarters Navy Order No 1, ordered the necessary units to advance to their prearranged points before the opening of operations.
Combined Fleet Operational Order No 1 was issued from the flagship Nagato in Saski Bay on 5 November, but was drafted at the time the operational policy of the Navy General Staff was informally announced and then was brought by the Commander in Chief and his staff officers to Tokyo where it was finalized after deliberation with the Navy General Staff of Imperial General Headquarters. (Appendix No 1)
On 22 November, the Combined Fleet issued the following top secret order to the Carrier Striking Force in preparation for the attack on Hawaii.
Combined Fleet Operation Order No. (not designated)
On board the Flagship Nagato in Hiroshima Bay, 22 November 1941
Commander in Chief of the Combined Fleet, Yamamoto Isoroku
Combined Fleet Order
1. The Carrier Striking Force, while keeping its movements strictly secret, will sail from Hitokappu Bay according to special orders and, taking the strictest precautions against submarines and aircraft, will advance to the Hawaii area, and, at the very beginning of the war, will resolutely launch an attack against the main force of the United States Fleet in the Hawaii area and deal it a vital blow.
The first attack from the air will be prearranged to be made on X day (which will be designated later) at daybreak. After the air raid has ended, the Carrier Striking Force, while guarding against counterattacks by the enemy, will consolidate
the entire force, quickly disengage from the economy and at once return to the Homeland.
2. Should negotiations with the United States reach a successful conclusion, the Carrier Striking Force will at once return to the Homeland for assembly.
In order to insure the issuance of orders immediately after the decision of the Cabinet Council was made, and also to preserve the strictest secrecy, this order also was completed by the staff officers of the Combined Fleet at the headquarters of the General Naval Staff in Tokyo.
As the Cabinet was unable to reach an early decision, it was impossible for the Combined Fleet to make formal operational preparations. In consequence, Combined Fleet and all operational forces under its command had many problems to overcome at the last moment. This situation also clearly demonstrated that no military command could be exercised without being subject to the formal decision of the will of the Government.
Summary of Political Strategy Prior to Outbreak of War
The Pacific war developed from the China Incident, which, in turn, was the outcome of the Manchurian Incident.
Because of her limited natural resources, the economic situation always has played a tremendous part in forming the foreign policy of Japan. One of the main circumstances which forced Japan to take drastic action in Manchuria was the economic panic which swept the world in 1929, and Japan's contention is that the Manchurian Incident in September 1931 cannot be ascribed to an expansionist policy but rather to the need to defend the rights and interests that Japan had acquired in Manchuria as a result of the Russo-Japanese war.
With the establishment of Manchukuo in March 1932, Japan formally recognized this state. China's extreme anti-foreign ideologies which, until this time, had been concentrated on Great Britain, began to shift toward Japan, and Chinese authorities adopted a strong anti-Japanese policy. This resulted in a boycott of Japanese goods and, in many cases, of public insult of the Japanese people. At the same time, China brought the case of Manchukuo before the League of Nations, and, on 24 February 1933, the League adopted a resolution calling for the non-recognition of Manchukuo. The United States, although not a member of the League of Nations, firmly upheld this resolution. As a result, Japan withdrew from the League of Nations.
Early in 1933, the Hitler regime came into power in Germany and,
in October of the same year, Germany also withdrew from the League of Nations. At the end of 1936, the Japanese-German anti-Comintern Pact and the Japanese-Italian agreement were signed, thus drawing Japan closer to these two nations.
In the meantime, anti-Japanese feeling, encouraged by the Western Powers, daily grew stronger in China, until, in January 1932, hostilities broke out between the Japanese and Chinese troops in Shanghai. It was not until several months later that the Chinese-Japanese Agreement ended the trouble.
On the night of 7 July 1937, Japanese forces garrisoned at Feng-Tai, southwest of Peiping, clashed with the Chinese 29th Army in the vicinity of the Marco Polo Bridge in Peiping. This was the beginning of the China Incident, which, in spite of all efforts to localize it, fanned out all over China.
Traditionally, the Japanese Army always had regarded Soviet Russia as the potential enemy of Japan, while the Navy considered the United States as the greatest menace to Japan's security. Japan was, at all times, desperately short of resources and Manchukuo could supply only part of her requirements. The Navy looked to the resources of the southwest Pacific to make Japan self-sufficient, while the Army believed that Japan should advance into North China to the area bordering on Manchukuo, which had large reserves of iron, coal, cotton, wool and salt. Under the circumstances, neither service desired to be committed to a long war in China. The Navy was afraid that if the
China Incident was not localized, the necessary help that it would be required to give the Army would impede its armament program against the United States. They also felt that the British might come to the assistance of the Chinese. The Army feared that the spread of the conflict might force a change in their disposition of troops against Soviet Russia, while financial circles warned that Japan was still, to a great extent, dependent upon the United States and Great Britain for vital materials.
On 20 November 1937, Imperial General Headquarters was established in Tokyo to centralize the conduct of the China Incident in the hands of the Army and Navy leaders, acting under direct authority of the Emperor.
On 1 April 1938, the National General Mobilization Law was promulgated to be effective 5 May. This Bill allowed State dictation of almost all phases of economic life.
On 17 June 1940, France surrendered to Germany and, on 20 June, French Indo-Chinese authorities were forced to submit to Japan's demands to ban the transit of Chiang-aid supplies through their country and agreed to Japanese inspectors being stationed at key points along the border. After further negotiations, on 30 August, France reluctantly agreed to the basic Japanese-French Indo-Chinese Agreement granting military facilities to Japan in French Indo-China, to become effective after details of the entry of Japanese forces into French Indo-China had been worked out by the local authorities. On 27 Septe-
ber, a joint statement was issued by the Japanese and French Indo-Chinese Governments stating that a satisfactory agreement had been reached at Hanoi on 22 September. In accordance with the agreement, Japanese forces proceeded to Hanoi on 5 October and powerful units advanced to Bachinh, east of Hanoi on the 10th. This advance was actually the first step toward the southward advance by the Japanese forces and set the stage for the Japanese entry into southern French Indo-China, America's all-out economic blockade of Japan and the outbreak of the Pacific War the following year.
The national policy at that time was governed by "The Basic National Policy" decided at the Cabinet meeting on 26 July 1940, and "The Principles to Cope with the Changing World Situation" decided at the Liaison Conference between Imperial General Headquarters and the Japanese Government on 27 July. The latter was of particular importance since it followed the proposals of Imperial General Headquarters and, as a national policy, had great significance in regard to opening hostilities in the Pacific. This policy also strengthened the ties between Japan, Germany and Italy.
On 27 September 1940, the Tripartite Pact was formally concluded. This further antagonized the Western Powers and bound Japan even closer to Germany and Italy.
The Japanese-Netherlands East Indies negotiations, begun in September 1940, finally ended in complete failure on 18 June 1941. Thereupon Japan took the second step in her southward advance - the
occupation of southern French Indo-China - in order to dominate the military situation in the southern area and force the Netherlands East Indies to accede to her demands. This led to the Netherlands East Indies absolute embargo of oil shipments to Japan and constituted a definite cause for the commencement of the Pacific War.
On 8 March 1941, the United States Senate passed the Lend-Lease Act, indicating her determination to assist Great Britain and the Chiang regime.
On 13 April 1941, the Japanese-Soviet Neutrality Pact was signed in Moscow, whereby each country undertook to remain neutral should the other be attacked by a third power.
In the meantime, diplomatic negotiations begun by Ambassador Nomura in Washington in February had reached a stalemate with the United States steadfastly refusing to accept terms at the expense of China's sovereignty and insisting on the withdrawal of Japanese forces from both French Indo-China and China.
On 26 July, the United States and Great Britain froze Japanese assets overseas and, on 1 August, an embargo was placed on all aviation gasoline to Japan.
On 17 August, the United States placed an over-all embargo against Japan, and, at the same time, President Roosevelt declared that he "could not tolerate Japan's advance by armed force and would not continue meetings unless Japan's expansionist activities ceased."
Meanwhile, Japan felt that the German invasion of Russia lessened
the likelihood of a Russian attack from the north, should she decide to go south. Public opinion at that time held that should Japan now hesitate to go to war she would lose the opportunity of reaping economic benefits of joint victory with Germany and Italy.
At the Imperial Conference of 6 September, Japan's preparations for war, in the event diplomatic negotiations failed, were thoroughly discussed, although it was still hoped that an understanding could reached through diplomacy. Diplomatic negotiations were continued but Imperial General Headquarters and the Planing Board persistently drew attention to the fact that Japan's resources were being depleted daily with no hope of replenishment while the United States was rapidly stockpiling armaments and constructing new ships and airplanes. They urged that a definite deadline be set for diplomatic negotiations and that all-out war plans and preparations be completed at the earliest possible date.
On 5 November, an Imperial Conference was held at which the national policy in anticipation of war was agreed upon. Army and Navy war preparations were accelerated, although the planned attack on Pearl Harbor was kept secret from all except those actually engaged in the planning. At the same time, it was decided that should diplomatic negotiations achieve success by 0000 hours on 1 December, the use force would be suspended.
After studying the Hull note, received from the United States on 26 November, which the Japanese Imperial General Headquarters and
Government regarded as an ultimatum, it was agreed formally on 1
December that the opening of hostilities was unavoidable. Therefore, the Cabinet meeting of 5 December and the Liaison Conference of 6 December decided on a draft of an Imperial Rescript announcing a state of war with the United States and Great Britain. This was submitted to the Emperor on 7 December and received his sanction on that day.
At 0215 hours on 8 December, Japanese troops attacked British forces at Kota Bharu in the Malaya area - the first battle in the Pacific war.
At 0320 hours on the same day, Japan launched air attacks on Pearl Harbor.