The attack on Pearl Harbor was a surprise military strike by the Imperial Japanese Navy Air Service upon USAball 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. USAball was a neutral country at the time; the attack led to its formal entry into World War II on the side of the Allies the next 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 USAball and Japanball over the future of the Pacific. Japanball's demands included that USAball end its sanctions against Japanball, cease aiding Chinaball in the Second Sino-Japanese war, and allow Japanball to access the resources of the Dutch East Indies. Anticipating a negative response from USAball, Japanball sent out its naval attack groups in November 1941 just prior to receiving the Hull note — USAball demanded that Japanball withdraw from Chinaball and French Indochinaball. Japanball 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 UKball, Netherlandsball, and those of USAball. Over the course of seven hours, there were coordinated Japanese attacks on the U.S.-held Philippinesball, Guam, and Wake Island and on the British Empire in Malaya, Singaporeball, and Hong Kongball.
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. Japanball 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 the home of the intelligence section), were not attacked. Japanese losses were light: 29 aircraft and five midget submarines were lost, and 64 servicemen were killed. Kazuo Sakamaki, the commanding officer of one of the submarines, was captured.
Japanball announced declarations of war on USAball 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 Japanball immediately after learning that their territory had also been attacked, while the following day (December 8) the United States Congress declared war on Japanball. On December 11, though they had no formal obligation to do so under the Tripartite Pact with Japanball, Germanyball, and Italyball each declared war on USAball, which responded with a declaration of war against Germanyball and Italyball. There were numerous historical precedents for the unannounced military action by Japanball, but the lack of any formal warning (required by part III of the Hague Convention of 1907), particularly while negotiations were still apparently ongoing, led President Franklin D. Roosevelt to proclaim December 7, 1941, "a date which will live in infamy".