World War Two: Philippines (Prewar (Part 1-4A); Japanese strategy for a war

By the summer of 1941, as the United States was beginning to strengthen the Philippines, Japan had reached “the crossroads of her fate.” The economic sanctions imposed by America, Great Britain, and the Netherlands had cut her off from the strategic materials necessary to support the war in China and threatened eventually to so weaken the Japanese economy as to leave Japan defenseless in a struggle with a major power. The leaders of Japan were faced with a difficult choice. They could either reach agreement with the United States by surrendering their ambitions in China and southeast Asia, or they could seize Dutch and British possessions by force.

The second course, while it would give Japan the natural resources so sorely needed, almost certainly meant war with Great Britain and the Netherlands. In the view of the Japanese planners, the United States would also oppose such a course by war, even if American territory was not immediately attacked. Such a war seemed less dangerous to Japan in the fall of 1941 than ever before and, if their calculations proved correct, the Japanese had an excellent chance of success. The British Empire was apparently doomed and the menace of Russian action had been diminished by the German invasion of that country and by the Japanese-Soviet neutrality pact.

The major obstacles to Japan’s expansion in southeast Asia was the United States. But Japanese strategists were confident they could deprive the United States of its western Pacific base in the Philippines and neutralize a large part of its Pacific Fleet at the start of the war. In this way they hoped to overcome America’s potential superiority and seize the southern area rapidly.

The Japanese Plan

Japanese strategy for a war with the United States, Great Britain, and the Netherlands was apparently developed in about six months by Imperial General Headquarters. [Statement of Lt Gen Masami Maeda, CofS 14th Army, 7 Mar 50, Allied Translator and Interpreter Section (ATIS), Document 56234, in Interrogations of Former Japanese Officers, Philippines-Japanese Invasion, Mil Hist Div, GHQ Far East Command (FEC) and Supreme Commander Allied Powers (SCAP), 2 vols., II. Joint Statements of Col Takushiro Hattori and Capt Sadatoshi Tomioka, chiefs of the Army and Navy Operations Sections, respectively, of Imperial GHQ,] Although this strategy was never embodied in one document, it can be reconstructed from separate Army and Navy plans completed by the beginning of November 1941. Thereafter it was modified only in minor respects. [May 49, ATIS Doc 50459, and of Lt Gen Shinichi Tanaka and Col Hattori, 3 May 49, ATIS Doc 52361, both in Statements of Japanese Officials on World War II, GHQ FEC, Mil Intel Sec, 4 vols., I, 352-53, IV, 196.]

Strategic Concepts; Wake Guam

The immediate objective of Japanese strategy was the capture of the rich Dutch and British possessions in southeast Asia, especially Malaya and the Netherlands Indies. To secure these areas the Japanese believed it necessary to destroy or neutralize the U.S. Pacific Fleet at Pearl Harbor, deprive the United States of its base in the Philippines, and cut America’s line of communications across the Pacific by the seizure of Wake and Guam. Once the coveted area to the south had been secured, Japan would occupy strategic positions in Asia and in the Pacific and fortify them immediately with all the forces available, chief reliance being placed on mobile naval and air forces. These positions were to form a powerful defensive perimeter around the newly acquired southern area, the home islands, and the vital shipping lanes connecting Japan with its sources of supply.

[The plan of operations worked out by Imperial GHQ about the middle of November 1941 was destroyed by fire. Certificate of Yozo Miyama, Chief, Archives Sec, 1st Demobilization Bureau, Defense Doc 2726, International Military Tribunal for the Far East (IMTFE). The description of Japanese strategic concepts is derived from the following documents: ( 1) Central Agreement Between the Japanese Navy and Army, (2) The Imperial Navy’s Course of Action in Operations Against U.S., Great Britain, and thc Netherlands, (3) Combined Fleet Top Secret Operation Order 1, 5 November 1941, and (4) Comments of Former Japanese Officers regarding The Fall of the Philippines. The first two are reproduced in United States Strategic Bombing Survey (USSBS), The Campaigns of the Pacific War (Washington, 1946), Apps. 13 and 14, pp. 43-49;. The orders and plans of the Army General Staff can be found in Hist Army Sec, Imperial GHQ; History of Southern Army 1941-1945, Japanese Studies in World War II, No. 21; 14th Army Opns, 2 vols., Japanese Studies in World War II, Nos. 1 and 2.]

The area marked for conquest formed a vast triangle, whose east arm stretched from the Kuril Islands on the north, through Wake, to the Marshall Islands. The base of the triangle was formed by a line connecting the Marshall Islands, the Bismarck Archipelago, Java, and Sumatra. The western arm extended from Malaya and southern Burma through Indochina, and thence along the China coast. The acquisition of this island-studded area would give to Japan control of the resources of southeast, Asia and satisfy the national objectives in going to war. Perhaps later, if all went well, the area of conquest could be extended. But there is no evidence that it was the intention of the Japanese Government or of the Army and Navy to defeat the United States, and so far as is known no plan was ever drawn up for that purpose. Japan apparently planned to fight a war of limited objectives and, having gained what it wanted, expected to negotiate for a favorable peace.

Operations to secure these objectives and others would begin on the first day of war when Japanese military and naval forces would go into action simultaneously on many fronts. Navy carrier-based aircraft would attack Pearl Harbor. Immediately after, joint Army and Navy air forces would strike American air and naval forces in the Philippines, while other Japanese forces hit British Malaya. After these simultaneous attacks, advance Army units were to be landed at various points in Malaya and the Philippines to secure air bases and favorable positions for further advances. The results thus obtained were to be immediately exploited by large-scale landings in the Philippines and in Malaya and the rapid occupation of those areas. At the same time Thailand was to be “stabilized,” Hong Kong seized, and Wake and Guam occupied. The conquest of the Bismarck Archipelago would follow the seizure of the last two islands.

The occupation of Java and Sumatra was to begin after this initial period. While Java was being attacked from the air, Singapore was to be taken under fire from the land side by Japanese forces moving down the Malay Peninsula. Once that fortress was reduced these forces were to move on to northern Sumatra. Meanwhile, other Japanese forces moving southward through the Netherlands Indies were to join those in Sumatra in the final attack on Java.

Japanese planners anticipated that certain events might require an alteration of these plans and accordingly outlined alternative courses of action. The first possibility was that the Japanese-American negotiations then in progress would prove successful and make war unnecessary. If this unexpected success was achieved all operations were to be suspended, even if the final order to attack had been issued. The second possibility was that the United States might take action before the attack on Pearl Harbor by sending elements of the Pacific Fleet to the Far East. In that event, the Combined Fleet would be deployed to intercept American naval forces. The attacks against the Philippines and Malaya were to proceed according to schedule.

If the Americans or British launched local attacks, Japanese ground forces were to meet these while air forces were brought into the area to destroy the enemy. These local operations were not to interrupt the execution of the grand plan. But if the United States or Great Britain seized the initiative by opening operations first, Japanese forces were to await orders from Imperial General Headquarters before beginning their assigned operations.

The possibility of a Soviet attack or of a joint United States-Soviet invasion from the north was also considered by the Japanese planners. If such an attack materialized, operations against the Philippines and Malay would be carried out as planned while air units would be immediately transferred from the home islands or China to destroy Russian air forces in the Far East. Ground forces were to be deployed to Manchuria at the same time to meet Soviet forces on the ground.

The forces required to execute this ambitious plan were very carefully calculated by Imperial General Headquarters. At the beginning of December 1941 the total strength of the Army was 51 divisions, a cavalry group, 59 brigade-size units, and an air force of 51 air squadrons. In addition, there were ten depot divisions in Japan. These forces were organized into area commands widely scattered throughout the Far East. The largest number of divisions was immobilized in China and large garrisons were maintained in Manchuria, Korea, Formosa, Indochina, and the home islands. Only a small fraction of Japan’s strength, therefore, was available for operations in southeast Asia and the Pacific.

In the execution of this complicated and intricate plan, the Japanese planners realized, success would depend on careful timing and on the closest co-operation between Army and Navy forces. No provision was made for unified command of the services. Instead, separate agreements were made between Army and fleet commanders for each operation. These agreements provided simply for co-operation at the time of landing and for the distribution of forces.

SOURCE: The Fall Of The Philippines by Louis Morton (United States Army Center of Military History)

World War Two: Philippines (Prewar Part 1-4B); Japanese Invasion Plans

World War Two: Philippines (Part 1-3B); Reinforcements

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