Pearl Harbor The road to war between Japan and the United States began in the 1930s, when differences over China separated the two nations. In 1931 Japan conquered Manchuria, which until then had been part of China. In 1937 Japan began a long and unsuccessful campaign to conquer the rest of China. In 1940, the Japanese government allied their country with Nazi Germany in the Axis Alliance and, the following year, occupied all of Indochina. The United States, which had important political and economic interests in East Asia, was alarmed by these Japanese moves. . The United States increased military and financial aid to China, embarked on a program to strengthen its military power in the Pacific, and cut off shipments of oil and other raw materials to Japan. Because Japan was poor in natural resources, its government saw these steps, particularly the oil embargo, as a threat to the nation's survival. Japan's leaders responded by deciding to seize the resource-rich territories of Southeast Asia, even though this move would surely provoke a war with the United States. The problem with the plan was the danger posed by the U.S. Pacific Fleet based at Pearl Harbor. Admiral Isoroku Yamamoto, commander of the Japanese fleet, devised a plan to immobilize the American fleet early in the war with a surprise attack. The key elements of Yamamoto's plans were meticulous preparation, the effect of surprise, and the use of aircraft carriers. and naval aviation on an unprecedented scale. In the spring of 1941, Japanese carrier pilots began training in the special tactics required by the Pearl Harbor attack plan. In October 1941, the Naval General Staff gave final approval to Yamamoto's plan, which called for the formation of a strike force commanded by Vice Admiral Chuichi Nagumo. It centered on six heavy aircraft carriers accompanied by 24 support ships. A separate group of submarines was to sink any American warships that escaped the Japanese carrier force. Nagumo's fleet gathered at the remote anchorage of Tankan Bay in the Kuril Islands and departed in utmost secrecy for Hawaii on November 26, 1941. The ships' route crossed the North Pacific and avoided normal sea routes. At dawn on December 7, 1941, the Japanese task force had approached undetected a point just over 200 miles north of Oahu. US aircraft carriers were not at Pearl Harbor at the time. On November 28, Admiral Kimmel dispatched USS Enterprise under Rear Admiral Willliam Halsey to deliver Marine Corps fighter aircraft to Wake Island.