The Japanese military leadership referred to the attack as the Hawaii Operation and Operation AI, and as Operation Z during its planning. The United States 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. (local time) on Sunday, December 7, 1941. naval base at Pearl Harbor in Honolulu, Hawaii, just before 8:00 a.m. The attack on Pearl Harbor was a surprise military strike by the Imperial Japanese Navy Air Service upon the United States against the U.S.
