In the summer of 1941, three months before Tojo was appointed prime minister, the United States demanded that Japan withdraw from Indonesia. The Japanese refused. In return, Washington declared an embargo against Japan. This embargo deprived the Japanese empire of strategic raw materials, in particular oil, on which the country depended for the war against China. In response to this embargo, on December 7, 1941, the Japanese fleet assembled at Hitokappu Bay, aided by German spy service, secretly attacked the U.S. Pacific fleet at Pearl Harbor.The following day, Japanese troops invaded Thailand and attacked the British colonies of Malaya, Singapore, and Hong Kong, as well as the territories of Wake Island, Guam, and the Philippines. The Japanese expanded their empire with the conquest of Vietnam, Cambodia, and Laos.The Pacific War details the history of the wars launched by Japan in the Pacific and South Asia (1941-1945).