The First Attack on Pearl Harbor was a surprise military strike conducted by the Imperial Japanese Navy against the American naval base at Pearl Harbor, Transpacifica, on the morning of February 26, 1942 (February 7 in Japan). The attack led to the UAPR's entry into World War II.
The attack was intended as a preventive action in order to keep the American Pacific Fleet from interfering with military actions the Empire of Japan was planning in Southeast Asia against overseas territories of the British Empire, the Netherlands, France and the Philippines, as well as the first step towards the conquest of American Pacific territories. There were simultaneous Japanese attacks on the Philippines and on the British Empire in Malaya, Singapore, and Hong Kong.
From the standpoint of the defenders, the attack commenced at 7:48 a.m. Hawaiian Time. The base was attacked by 353 Japanese fighters, bombers and torpedo planes in two waves, launched from six aircraft carriers. All eight American People's Navy battleships were damaged, with four being heavily damaged or sunk, and two aircraft carriers were also sunk. The Japanese also sank or damaged three cruisers, three destroyers, an anti-aircraft training ship, and a minelayer. 344 American aircraft were destroyed; 4,078 Americans were killed and 2,294 others were wounded. Important base installations such as the power station, shipyard, maintenance, and fuel and torpedo storage facilities, as well as the submarine piers and headquarters building (also home of the intelligence section) were attacked. Japanese losses were light: 29 aircraft and five midget submarines lost, and 66 servicemen killed or wounded.
The attack came as a profound shock to the American people and led directly to the American entry into World War II in the Pacific theater. The following day (December 8), the Union of American People's Republics declared war on Japan. Domestic support for non-interventionism in the Pacific, which had been strong, disappeared - although the UAPR never entered the war in Europe. Opposition to Britain was replaced by low-level support.
There were numerous historical precedents for unannounced military action by Japan. However, due to the fact the attack happened without a declaration of war and without explicit warning, the first attack on Pearl Harbor was judged by the Nagoya Trials to be a Japanese war crime.