1937: Sino-Japanese WarThe Japanese had already invaded China before World War II started in Europe. U.S. President Roosevelt signed an executive order in May of 1940 allowing U.S. military personnel to resign from the service so that they could participate in a covert operation in China. Hence was born the All Volunteer Group, more commonly known as Chennault's Flying Tigers. With the United States and other countries cutting exports to Japan, Japan decided to bomb Pearl Harbor on 7 December 1941 without warning or declaration of war. Severe damage was done to the American Pacific Fleet, although the aircraft carriers escaped as they were at sea. Japanese forces simultaneously invaded the British possessions of Malaya and Borneo and the American occupied Philippines, with the intention of seizing the oilfields of the Dutch East Indies. The British island fortress of Singapore was captured in what Churchill considered one of the most humiliating British defeats of all time.

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