<P> The war in Europe came to an official end on V-E Day, 8 May 1945 . </P> <P> Because of Japanese advances in French Indochina and China, the United States, in coordination with the British and Dutch, cut off all oil supplies to Japan, which had imported 90% of its oil . The oil embargo threatened to grind the Japanese military machine to a halt . Japan refused American demands to leave China and decided that war with the United States was inevitable; its only hope was to strike first . President Roosevelt had months earlier transferred the American fleet to Hawaii from California in order to deter the Japanese . Admiral Isoroku Yamamoto argued the only way to win the war was to knock out the powerful main American fleet immediately . His elaborately trained fleet approached within 200 miles of Hawaii without being detected . Admiral Chūichi Nagumo held tactical command . Over a five - hour period his six carriers sent two waves of 360 dive - bombers, torpedo planes, and fighters . They destroyed or severely damaged eight battleships, ten smaller warships, and 230 aircraft; 2,403 American servicemen and civilians were killed . Japanese losses were negligible--29 planes shot down (several American planes were also shot down by anti-aircraft fire). Commander Minoru Genda, the chief planner of the raid, begged Nagumo to strike again at the shore facilities, oil storage tanks, and submarines, and to hunt down the American carriers that were supposedly nearby . But Nagumo, having just smashed the Americans in one of the greatest victories of naval history, decided not to risk further action . Japanese success was due to courage, good equipment, excellent pilots, total surprise, and above all, a daring and imaginative plan . To even reach Pearl Harbor, they had to learn how to refuel at sea (a technique the US Navy already had worked out); to sink all those ships they used their superb electric torpedoes and perfected shallow - water bombing tactics . Surprise was decisive . While everyone knew that war was imminent, no one at Pearl expected an attack . Despite later rumors, there was no advance knowledge of the Japanese plan . The commanders had been complacent about routine defensive measures . Even if the defense had been more alert, the surprise and overwhelming power of the Japanese strike probably would have been decisive . In broader perspective, the attack was a failure . The lost battleships reflected obsolete doctrine and were not needed; the lost planes were soon replaced; the casualty list was short by World War II standards . Tokyo's calculation that the Americans would lose heart and seek a compromise peace proved wildly wrong--the "sneak attack" electrified public opinion, committing America with near unanimity to a war to the death against the Japanese Empire . </P> <P> Following the attack on Pearl Harbor, President Roosevelt officially pronounced 7 December 1941, as "a date which will live in infamy" and asked for a declaration of war on Japan before a joint session of Congress on 8 December 1941 . The motion passed with only one vote against it, in both chambers . Just three days later, on 11 December 1941 Adolf Hitler declared war on the United States, and had already remarked on the evening of the date of the Japanese attack that "We can't lose the war at all . We now have an ally which has never been conquered in 3,000 years". </P> <P> Within hours of Pearl Harbor Japanese air forces from Formosa destroyed much of the U.S. Far East Air Force, based near Manila . The Japanese army invaded and trapped the American and Filipino forces on the Bataan peninsula . Roosevelt evacuated General Douglas MacArthur and the nurses, but there was no way to save the trapped men against overwhelming Japanese naval power . MacArthur flew to Australia, vowing "I came out of Bataan and I shall return ." Major General Jonathan M. Wainwright surrendered on 8 May; the prisoners died by the thousands in the Bataan Death March and in disease - ridden Japanese prison camps where food and medicine were in very short supply . </P>

When did the united states officially entered ww2