Estimate of the Situation Prior to Outbreak of War
Progress of Revision of the Wartime Naval Organization
from November 1940 until the Outbreak of War
Chart 1 shows how surface craft were replenished and how the Navy shifted into a wartime organization.
Estimate of the Situation in Early November 1941
On 1 November 1941, at the Liaison Conference between the Japanese Government and Imperial General Headquarters, Navy Minister
Shimada made the following statement:
In the event of war, the Naval High Command believes that the Navy stands a very good chance of victory in both the early stage operations and the interception operations against the enemy fleet, with the present power ratio. However, should the war continue into its third year and become a long term war, according to comprehensive research by the various Navy departments, shortages of war materials and the inadequacy of Japan's industrial potential will then begin to have their effect on the Navy's strength. Under the latter conditions, it would be difficult for us to have any measure of confidence that we could bring the war to a victorious conclusion.
On the other hand, if we decide to continue diplomatic negotiations and later fail to bring them to a successful conclusion, we will be forced to open hostilities at a great operational disadvantage, caused by the delay. Consequently, although there is e great risk in beginning the war now we must realize that there is also a great risk in depending upon negotiations unless we can be certain of the final outcome. It would seem, therefore, that whether we continue diplomatic negotiations or open hostilities, great risks and difficulties are involved. The risks involved in each case have to be weighed in order to arrive at an estimate of the general situation. The risks attendant upon the opening of hostilities are enormous and it must be realized that once committed we cannot
Chart 1 152-01.doc
Changes of Organization Japanese Navy from November 1940 to the Outbreak of the war.
turn back; therefore, if at all possible, we should use diplomacy. However, if we are not confidant of the success of the diplomatic negotiations, then we have no alternative but to take up arms...
When we initiate hostilities against our powerful adversary, we must make our noble and just cause explicitly clear to our people and to the world at large. In conjunction with this, we must earnestly study the best methods of guiding our people in war.
On 4 November, at the Joint Army-Navy Supreme Military Council meeting , the gist of Chief of Navy General Staff Nagano's speech was as follows:
If we allow the present state of affairs to continue indefinitely, our Empire will not only ultimately lose its war potential but will be placed strategically at a great disadvantage. The Government is now earnestly striving to break the stalemate in the present crisis through diplomatic channels. We are heartily in accord with this. At the same time, however, we must be fully prepared should our Empire, with the failure of diplomatic negotiations, be forced to take up arms. It is the view of Imperial General Headquarters that Japan must continue all-out operational preparations and be ready for war in the event
 The Joint Army-Navy Supreme Military Council meeting was held on 4 November 1941, the day before the Imperial Conference was convoked. The Emperor had asked the Council whether it was advisable to proceed with war preparations as a military measure to meet the worst possible situation - namely, in the event negotiations with the United States failed to reach a satisfactory conclusion. The Council meeting held in the afternoon of 4 November was presided over by Field Marshal Prince Kanin and was honored by the presence of the Emperor. The agendum was "National defense and the use of arms in implementing the national policy of Imperial Japan," and the issue; "Japan, in order to free herself from the present crisis must take up arms against the United States, Britain and the Netherlands and thereby safeguard her national existence and security and establish a new order in Greater East Asia. The time to initiate military operations should be set for the beginning of December." After explanations, questions and various views were presented, the Council unanimously agreed that Japan should go to war.
of such a failure. In my opinion, in the present situation, continuance of these operational preparations will serve to further the negotiations.
Should Japan's negotiations with the United States fail and war begin between Japan and the United States, Great Britain and the Netherlands, I believe that, on the basis of the present strength of the operating forces in the Pacific, we have a good chance of defeating the enemy both in the first phase operations and in the interception operations against the enemy fleet, provided hostilities begin in early December. If we are successful in the first phase operations, we should be able to secure strategical key points in the southwest Pacific and thus be in a position to wage a long war of attrition. In a war against the United States and Great Britain, we have no sure way of bringing the enemy to his knees, so in all probability the war would be a protracted one. We must, therefore, be prepared for a long war both spiritually and materially. The outcome of a long war depends on various physical and metaphysical factors, on our total war potential and on the development of the world situation. It is difficult, under the circumstances, to foretell now whether we have a chance of winning the war several years hence.
It the Imperial Conference on 5 November, the Chief of the Army General Staff Sugiyama stated:
The armies in the southern territories are steadily being reinforced. Their present strengths are as follows:
Malaya 60-70,000 troops and about 320 planes. Philippines About 42,000 troops and about 170 planes. Dutch East Indies About 85,000 troops and about 300 planes. Burma About 35,000 troops and about 60 planes.
Compared with the forces in these territories before the outbreak of war in Europe, the Army in Malaya has increased about eight times, that in the Philippines about four times, that in the Dutch East Indies about two and a half times and that in Burma about five times. The total strength of the armies these territories amounts to a little more than 200,000; we must expect their rate of increase to become greater with time.
The ground forces in these territories as essentially native armies formed around a nucleus of white troops, which constitute about 30 per cent of the forces. They are not well trained and their combat ability is generally below standard, However, they
are inured to tropical weather and climate. We must also remember that their planes perform well and their pilots are quite good.
From the operational standpoint, each day of delay in the commencement of military operations will place us at a greater disadvantage so that finally it will become impossible to conduct operations for the following reasons:
1. Japan will not be able to keep pace with the United States in an armament race, especially in aircraft production.
2. American defenses in the Philippines, as well as other American military preparations, will make rapid headway.
3. Defensive coordination of the United States, Great Britain, the Netherlands and China will be further stepped-up and their combined defensive power in the southern area will be increased vastly.
4. If the war is delayed until spring, operational action the northern Pacific and Siberia would become possible. Japan then might be committed to fight on the northern and southern fronts at the same time.
In addition to the above, weather conditions in the anticipated theater of operations, which are a very important factor in the present operations plan, will not allow indefinite postponement of war. Therefore, in order to initiate our military operations immediately upon the completion of present operational preparations, I should like to set the time as early December.
The major part of the Army's initial operations in the southern areas will consist of landings against strongly defended distant enemy bases. These operations will have to be conducted in scorching heat, while repelling hostile submarines and airplane attacks. We must, therefore, except to have to surmount considerable difficulties. However, from the over-all standpoint, whereas the enemy forces will be scattered over wide areas separated from each other by sea, rendering it difficult for them to coordinate movements, we will be able to consolidate our forces in surprise attacks to destroy the enemy piecemeal. I am confident, therefore, that close coordination between the Army and the Navy will insure the success of our landing operations. In regard to the operations after the landing, comparing organization, equipment, the quality and the number of men of our forces and the enemy, I am confident that victory will be ours.
After the conclusion of these operations, even if we did our best to terminate the war as early as possible by diplomatic and military means, especially through the exploitation of our naval successes, we probably would still have to be prepared for a long war. However, since we could capture enemy military and air bases and make our position invulnerable, I believe we could use various means to frustrate the enemy's intentions.
As to our defense against the Soviet Union and our China operations after we embark on the Southern Operations, we intend to hold generally our present military power which will enable us to strengthen our defenses against the Soviet Union and to continue our operations in China. I think we can exploit our successes in the Southern Operations so that they would help conclude the China Incident.
The Soviet field armies have suffered severe losses at the hands of the German Army, and the Soviet's munitions industries productive capacity, too, has decreased enormously. The Far Eastern Red Army, furthermore, has sent, since last spring, about 13 divisions of infantry, about 1,300 tanks and no less than 1,300 planes eastward to European Russia, and its fighting strength, I believe, is declining materially and spiritually. Therefore, as long as our Kwantung Army maintains a strong position there is little likelihood that the Soviet Union, on its own initiative, will attack us.
However, since there is the possibility that the United States might force the Soviet Union to allow the United States to build air and submarine bases in its far eastern territory as northern bases of attack against Japan, and the Soviet Union might not be in a position to reject the demand, we must expect hostile submarines and air action from the northern area. The above action, should it occur, could precipitate war between Japan and the Soviet Union. Since we cannot disregard this possibility altogether, we must conclude our Southern Operations as early as possible and be fully prepared to meet the above possibility.
In regard to the relation between military operations and diplomacy, to this day our operational preparations have been restricted, according to the decisions of the Imperial Conference of 6 September, so that they would not jeopardize diplomatic negotiations, but henceforth the preparations must be accelerated with the intention of making war and we must leave no stone unturned to develop our military strength to the fullest by the beginning of December. This action might provoke the United States and Britain, but I believe that such preparation will assist our
diplomatic negotiations. Needless to say, we will cancel the use of force if our diplomacy should succeed before 2400 hours, 30 November. However, should diplomacy fail to achieve its end by this time, I believe we should , upon receiving Imperial assent, initiate our military operations before the chance is lost and do our utmost to attain our military objective.
Comparison of Japanese and Estimated Allied Strength in the Pacific Immediately Prior to the War
Allied Naval Strength
The following is the estimated naval strength of the United States, Great Britain and the Netherlands in the Pacific areas at the end of November 1941.
United States Fleet (the Pacific area) Battleships ......................... 11 Aircraft carriers ................... 5 Heavy cruisers ...................... 16 Light cruisers ...................... 14 Destroyers .......................... 84 Submarines .......................... 30 Total ............................ 160; 911,575 tons Others ........................... 52; 301,800 tons Grand total ...................... 212; 1,213,375 tons U. S. Naval Vessels in Central and South America Destroyers .......................... 2; 2,180 tons Others .............................. 2; 4,000 tons Total ........................... 4; 6,180 tons U. S. Far East Fleet Heavy cruiser ....................... 1 Light cruiser ....................... 1 Destroyer ........................... 14 Submarines .......................... 17 Others .............................. 17; 42,300 tons
The Soviet Far East Fleet Destroyers .......................... 2 Submarines .......................... more than 60 Total ............................ more than 62; 30,00 tons Others ........................... undetermined number Australian Navy Heavy cruiser ....................... 1 Light cruiser ....................... 1 Destroyer ........................... 5 Others .............................. 7; 7,246 tons New Zealand Navy Light cruiser ....................... 2; 4,170 tons Others .............................. 3; approximately 2,120 tons British Asiatic Fleet Battleships ......................... 1 Light cruisers ...................... 4 Destroyers .......................... 4 Submarines .......................... 15 Others .............................. 26; 37,101 tons Royal Netherlands Fleet Cruisers ............................ 5 Destroyers .......................... 8 Submarines .......................... 19 British East Indies Fleet Heavy cruiser ....................... 3; 9,580 tons Aircraft carriers ................... 2 Destroyer ........................... 8
Chart 2-a 152-02.doc
Estimated American, British and Dutch Air and Land Strengths Prior to Pacific War
Chart 3 152-03.doc
Comparison of Naval Strength of Japan and the United States Pacific and Asiatic Fleets at the Beginning of December, 1941
An estimate of Japanese and United States' naval strength and anticipated changes thereto, is given hereunder:
Prior to the outbreak of the war, the Japanese Navy estimated the United States' 10 to Japan's 7 or thereabouts as the ratio of the vessels possessed by the United States and the Japanese navies. However, at the war's beginning, considering the fact that Japan possessed 14 obsolete vessels totaling about 60,000 tons (which included the Fuji, the Kitagami and several submarines) while the United States must have had far more useless vessels which were not properly equipped for war, the Japanese Navy judged that the ratio of vessels actually capable of action on the sea was about 10 (United States) to 7.5 (Japan). The United States air strength capable of participating in naval operations was estimated at some 5,500 naval planes plus 100 army strategic bombers. Against this, Japanese Navy operational aircraft totaled 3,300, of which 1,699 were incorporated into the Combined Fleet to participate in offensive operations. Since American air strength was widely dispersed, the strength which the United States could immediately use against Japan was estimated at not more than 2,600, even when both army and Navy planes were taken into consideration. The Japanese Navy, therefore, expected that, if the Japanese Army air strength was taken into consideration, the air battle in the initial stage would be in favor of Japan.
Next, the Japanese Navy estimated the changes in naval strength ratio between Japan and the United States for 1942 and after as follows:
according to the then existing Japanese Navy's armament plan, the naval forces were to be increased by about 390,000 tons (130,000 tons a year) by the end of 1944. In addition, vessels completed by wartime emergency shipbuilding based upon the War Preparation Plan and the Fifth Armament Replenishment Program which was expected to be started in the near future, should be taken into consideration.
It was, however, believed that it would be difficult to build 200,000 tons a year. If Japan succeeded in concentrating the entire productive resources of the country for shipbuilding at the same time the war was begun, it was thought it might be possible to build even more vessels than the 200,000 tons a year. If the national resources namely, financial, material, technical resources and industrial capacity of the nation - were taken into account, 300,000 tons was considered the maximum that could be achieved.
On the other hand, the United States shipbuilding capacity was estimated at well over three times that of Japan. Furthermore, should the United States convert many of her merchant vessels into combat ships (above estimate of Japan's shipbuilding capacity included such conversion of merchant ships) and mass produce ships, it was believed that the United States could build five to six times as many ships as Japan without much difficulty. Moreover, on the basis of vessels under construction or in the planning stage at the end of 1941, the United States had more than 1,900,000 tons of ships against lass than 320,000 tons in Japan. The Japanese Navy, therefore, was forced to
conclude that Japan's ratio of naval strength against the United States would, even when viewed most optimistically, be 50 per cent or thereabouts in 1943 and 30 per cent or even less in 1944.
The estimate of the productive capacity of aircraft in Japan and in the United States was as follows:
Japan (Navy only) United States  1942 4,000 planes 47,900 planes 1943 8,000 " 85,000 " 1944 12,000 " more than 100,000 "
Therefore, the United States' capacity was more than 10 times that of Japan. Japan expected Army plane production to be about equal to the Navy's but it was almost impossible to use the Army air strength in sea operations against the United States due to training and technical and performance differences existing in the army and Navy air forces. Thus, even when aircraft available to the United States in the Pacific was scaled down to about 70 per cent of all manufactured be cause of the extended United States supply line and the necessity for supply to other theaters, the United States was estimated to have an aircraft replenishment capacity seven to eight times as large as Japan.
 United States planes included both Army and Navy. However, this was an estimate of air strength that could operate over the water. United States Army planes could operate over water, whereas, at this time, Japanese Army planes could be used only over land.
Such being the case, there was no doubt that the difference in air strength would become far greater than the difference in naval strength and Japan had, moreover, to expect the ratio to become even less favorable with the passage of time.
On the basis of the above estimate, Japan's Navy operations had to be aimed at dealing a crushing blow to the United States Fleet in the initial stage of the war and thereafter destroying enemy forces wherever they might be found while engaging the enemy fleet in a decisive fight at the earliest time possible. Throughout the operations, moreover, the Navy must constantly whittle the enemy fleet down to prevent the difference in strength from becoming excessively favorable to the enemy.
Chart 4 152-04.doc
Organization of Japanese Navy at the Beginning of the War
Chart 5 152-05.doc
Naval Base Force
Chart 6 152-06.doc
China Area Fleet
The Organization of Inner Combat Force Yokosuka Naval District Force Kure Naval District Force Maizuru Naval District Force Ominato Naval District Force Osaka Guard District Force Sasebo Naval District Force Chinhai, Mako and Port Arthur Guard District Force (Details are omitted.) Chart 8 The Organization List of Supply Force The outer zone force Homeland Agencies (Details are omitted.)