Pearl Harbor attack, (December 7, 1941), surprise aerial attack on the U.S. naval base at Pearl Harbor on Oahu Island, Hawaii, by the Japanese that precipitated the entry of the United States into World War II. The strike climaxed a decade of worsening relations between the United States and Japan. Japan’s invasion of China in 1937, its subsequent alliance with the Axis powers (Germany and Italy) in 1940, and its occupation of French Indochina in July 1941 prompted the United States to respond that same month by freezing Japanese assets in the United States and declaring an embargo on petroleum shipments and other vital war materials to Japan. By late 1941 the United States had severed practically all commercial and financial relations with Japan. Though Japan continued to negotiate with the United States up to the day of the Pearl Harbor attack, the government of Prime Minister Tōjō Hideki decided on war.
The extent of the disaster and the unpreparedness of the U.S. military provoked considerable criticism. Adm. Husband Kimmel and Gen. Walter Short, the Navy and Army commanders on Oahu, were relieved of duty, and official investigations were begun at once. Some historians and others went so far as to accuse President Roosevelt of having invited the attack (or at least done nothing to stop it) in order to bring the United States into the war against the Axis. (See Sidebar: Pearl Harbor and the “back door to war” theory.) However, later investigations indicated that, while U.S. officials had been aware that an attack by Japan was probable, they had no knowledge of the time or place at which it would occur.