Greater East Asia War in the Pacific

The Greater East Asia War (大東亜戦争) was a term used, at least publicly in December of 1941, by Japan's Imperial General Headquarters (Imperial GHQ) to refer to the conflict that followed (and ultimately reversed) Japan's invasions in the 1930s and early 1940s of other nations in eastern Asia and the Pacific. This war is more commonly known as the Pacific War of World War II.

Sanctions

Economic sanctionss imposed by the United States, United Kingdom, and the Netherlands against Japan in response to the Japanese invasions of China progressively weakened the Japanese economy. The Japanese government saw its choice as between:

relieving the sanctions by abandoning the war in China, or

replacing the withdrawn resources elsewhere in the region. Their decision was for extensive military operations.

War Plans

It is believed that the Imperial General Headquarters began planning the Greater East Asia War in April or May of 1941.

Attacking the Allies

The key objective was for the Southern Expeditionary Army Group to seize economic resources under the control of the United Kingdom and the Netherlands, notably in, respectively, Malaya (now Singapore and part of Malaysia), and the Netherlands East Indies (now Indonesia). They deemed the alliance of both these European nations with the United States as requiring this eastern plan:

initially, attacking the US Pacific Fleet at Pearl Harbor, Hawaii, with carrier-based aircraft of the Combined Fleet, and

following this attack with

* seizure of the Philippines, and

* cutting the US lines of communication by seizing Guam and Wake.

Their southern plans called for:

attacking Malaya and Hong Kong, and

following with attacks against

* the Bismarck Archipelago,

* Java, and

* Sumatra.

isolating Australia and New Zealand

Following completion of these objectives, the strategy would turn defensive, primarily holding their newly acquired territory.

By November these plans were essentially complete, and were modified only slightly over the next month. Japanese military planners' expectation of success rested on the United Kingdom and the Soviet Union being unable to effectively respond to a Japanese attack because of the threat posed to each by Germany; the Soviet Union was even seen as unlikely to commence hostilities.

Contingencies

There is no evidence that the Japanese planned to defeat the United States; the alternative would be negotiating for peace after their initial victories. In fact, the Imperial GHQ noted that should acceptable negotiations be reached with the Americans, the attacks were to be canceled -- even if the order to attack had already been given.

They also planned, should the US transfer its Pacific Fleet to the Philippines, to intercept and attack this fleet enroute with the Combined Fleet.

Should the United States or Britain attack first, the plans further stipulated the military were to hold their positions and wait for orders from GHQ. The planners noted that attacking the Philippines and Malaya still had possibilities of success, even in the worst case of a combined preemptive attack including Soviet forces.