The attack on Pearl Harbor was a surprise military strike by the Imperial Japanese Navy Air Service upon the United States against the U.S. Naval base at Pearl Harbor in Honolulu, Hawaii, just before 8:00 a.m. (local time) on Sunday, December 7, 1941. The United States was a neutral country at the time; the attack led the U.S. to formally enter World War II on the side of the Allies the following day. The Japanese military leadership referred to the attack as the Hawaii Operation and Operation AI, and as Operation Z during its planning.The attack was preceded by months of negotiations between the U.S. and Japan over the future of the Pacific. Japanese demands included that the U.S. end its sanctions against Japan, cease aiding China in the Second Sino-Japanese war, and allow Japan to access the resources of the Dutch East Indies. Anticipating a negative response from the US, Japan sent out its naval attack groups in November 1941 just prior to receiving the Hull note—the U.S. demand that Japan withdraw from China and French Indochina. Japan intended the attack as a preventive action. Its aim was to prevent the United States Pacific Fleet from interfering with its planned military actions in Southeast Asia against overseas territories of the United Kingdom, the Netherlands, and those of the United States. Over the course of seven hours there were coordinated Japanese attacks on the U.S.-held Philippines, Guam, and Wake Island and on the British Empire in Malaya, Singapore, and Hong Kong.The attack commenced at 7:48 a.m. Hawaiian Time (6:18 p.m. GMT). The base was attacked by 353 Imperial Japanese aircraft (including fighters, level and dive bombers, and torpedo bombers) in two waves, launched from six aircraft carriers. Of the eight U.S. Navy battleships present, all were damaged, with four sunk. All but USS Arizona were later raised, and six were returned to service and went on to fight in the war. The Japanese also sank or damaged three cruisers, three destroyers, an anti-aircraft training ship, and one minelayer. More than 180 US aircraft were destroyed. A total of 2,403 Americans were killed and 1,178 others were wounded, making it the deadliest event ever recorded in Hawaii. Important base installations such as the power station, dry dock, shipyard, maintenance, and fuel and torpedo storage facilities, as well as the submarine piers and headquarters building (also home of the intelligence section) were not attacked. Japanese losses were light: 29 aircraft and five midget submarines lost, and 64 servicemen killed. Kazuo Sakamaki, the commanding officer of one of the submarines, was captured.
Japan announced declarations of war on the United States and the British Empire later that day (December 8 in Tokyo), but the declarations were not delivered until the following day. The British government declared war on Japan immediately after learning that their territory had also been attacked, while the following day (December 8) the United States Congress declared war on Japan. On December 11, though they had no formal obligation to do so under the Tripartite Pact with Japan, Germany and Italy each declared war on the U.S., which responded with a declaration of war against Germany and Italy.
While there were historical precedents for the unannounced military action by Japan, the lack of any formal warning as required by the Hague Convention of 1907 and the perception that the attack was unprovoked, led then U.S. President Franklin D. Roosevelt, in the opening line of his speech to a Joint Session of Congress the following day, to famously label December 7, 1941 "a date which will live in infamy".
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