The Attack on Pearl Harbor was a major event in World War II and marked the moment America became actively involved in conflict after Imperial Japan launched a surprise attack on Pearl Harbor on December 7th, 1941; utilizing what would become infamous as "Kamikaze" suicide-tactics.
The Attack on Pearl Harbor (which resulted in the loss of 2,403 American servicemen and 68 civilians) was effectively a declaration of war and began what would become a brutal battle between America and Japan - as well as the other countries in the alliance that would become known as the Axis Powers. America joined the war specifically one day after the attack.
The Japanese Prime Minister, Hideki Tojo ordered The attack. It commenced at 7:48 a.m. Hawaiian Time (18:18 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. All eight U.S. Navy battleships were damaged, with four sunk. All but the USS Arizona and USS Utah 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. One hundred eighty-eight U.S. aircraft were destroyed; 2,403 Americans were killed and 1,178 others were wounded. 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. One Japanese sailor, Kazuo Sakamaki, was captured.
The surprise attack came as a profound shock to the American people and led directly to the American entry into World War II in both the Pacific and European theaters. The following day, December 8th, the United States declared war on Japan, and several days later, on December 11, Germany and Italy each declared war on the U.S. The U.S. responded with a declaration of war against Germany and Italy. Domestic support for non-interventionism, which had been fading since the Fall of France in 1940, disappeared.
There were numerous historical precedents for unannounced military action by Japan, but the lack of any formal warning, particularly while negotiations were still apparently ongoing, led President Franklin D. Roosevelt to proclaim December 7th, 1941, "a date which will live in infamy". Because the attack happened without a declaration of war and without explicit warning, the attack on Pearl Harbor was later judged in the Tokyo Trials to be a war crime.