The attack on Pearl Harborwas 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, Territory of 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 to its formal entry into World War II 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 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 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.
When was the attack on Pearl Harbor
December 7, 1941