Pacific War (Central Victory)

Conflict between China and Japan
By 1937, Japan controlled Manchuria and was ready to move deeper into China. The Marco Polo Bridge Incident (July 7, 1937) provoked full scale war between China and Japan. The Nationalist and Communist Chinese suspended their civil war to form a nominal alliance against Japan, and the Soviet Union quickly lent support by providing large amount of materiel to Chinese troops. The Japanese achieved major military victories in Shanghai, Nanjing, and Wuhan, but world opinion—in particular in the United States—condemned Japan, especially after Panay Incident.

In 1939, Japanese forces tried to push into the Soviet Far East from Manchuria. They were soundly defeated in the Battle of Khalkhin Gol by a mixed Soviet and Mongolian force led by Georgy Zhukov. This stopped Japanese expansion to the north, and Soviet aid to China ended as a result of the signing of the Soviet–Japanese Neutrality Pact at the beginning of its war against Germany.

In September 1940, Japan decided to cut China's only land line to the outside world by seizing Indochina, which was controlled at the time by Vichy France. Japanese forces broke their agreement with the Vichy administration and fighting broke out, ending in a Japanese victory. On September 27 Japan signed a military alliance with Germany and Italy, becoming one of the three Axis Powers. In practice, there was little coordination between Japan and Germany, by which time the U.S. was deciphering their secret diplomatic correspondence.

By 1941 the conflict had become a stalemate. Although Japan had occupied much of northern and central China, the Kuomintang had retreated to the interior with a provisional capital set up at Chungking while the Chinese communists remained in control of base areas in Shaanxi. In addition, Japanese control of northern and central China was somewhat tenuous, in that Japan was usually able to control railroads and the major cities ("points and lines"), but did not have a major military or administrative presence in the vast Chinese countryside. The Japanese found its aggression against the retreating and regrouping Chinese army was stalled by the mountainous terrain in southwestern China while the Communists organised widespread guerrilla and saboteur activities in northern and eastern China behind the Japanese front line.

Japan sponsored several puppet governments, one of which was headed by Wang Jingwei. However, its policies of brutality toward the Chinese population, of not yielding any real power to these regimes, and of supporting several rival governments failed to make any of them a viable alternative to the Nationalist government led by Chiang Kai-shek. Conflicts between Chinese communist and nationalist forces vying for territory control behind enemy lines culminated in a major armed clash in January 1941, effectively ending their co-operation.

Japanese strategic bombing efforts mostly targeted large Chinese cities such as Shanghai, Wuhan and Chongqing, with around 5,000 raids from February 1938 to August 1943 in the later case. "Japanese strategic bombing campaigns devastated Chinese cities, killing more than 260,000 noncombatants."

Tensions between Japan and the West
In an effort to discourage Japanese militarism, Western powers including Australia, the United States, and Britain stopped selling iron ore, steel and oil to Japan, denying it the raw materials needed to continue its activities in China and French Indochina. In Japan, the government and nationalists viewed these embargos as acts of aggression; imported oil made up about 80% of domestic consumption, without which Japan's economy, let alone its military, would grind to a halt. The Japanese media, influenced by military propagandists, began to refer to the embargoes as the "ABC ("American-British-Chinese") encirclement" or "ABC line".

Faced with a choice between economic collapse and withdrawal from its recent conquests (with its attendant loss of face), the Japanese Imperial General Headquarters began planning for a war with the western powers in April or May 1941.

The key objective was for the Southern Expeditionary Army Group to seize economic resources under the control of the United Kingdom, most notably those in Malaya, known as the "Southern Plan". It was also decided—because of the close relationship between the UK and United States, and the (mistaken) belief the US would inevitably become involved—Japan would also require an "eastern plan".

The eastern plan required
 * initial attacks on 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 U.S. lines of communication by seizing Guam and Wake.

The southern plans called for:
 * attacking Malaya and Hong Kong, and
 * isolating Australia and New Zealand

Following completion of these objectives, the strategy would turn defensive, primarily holding their newly acquired territory while hoping for a negotiated peace.

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.

The Japanese leadership was aware that a total military victory in a traditional sense against the USA was impossible; the alternative would be negotiating for peace after their initial victories, which would recognize Japanese hegemony in Asia. In fact, the Imperial GHQ noted, should acceptable negotiations be reached with the Americans, the attacks were to be canceled—even if the order to attack had already been given. The Japanese leadership looked to base the conduct of the war against America on the historical experiences of the successful wars against China (1894–95) and Russia (1904–5), in both of which a strong continental power was defeated by reaching limited military objectives, not by total conquest.

They also planned, should the U.S. transfer its Pacific Fleet to the Philippines, to intercept and attack this fleet en route with the Combined Fleet, in keeping with all Japanese Navy prewar planning and doctrine.

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 attacking the Philippines and Malaya still had possibilities of success, even in the worst case of a combined preemptive attack including Soviet forces.