The Japanese attack on Pearl Harbour, also known as the Battle of Pearl Harbour, took place on the morning of December 7, 1941, in the Hawaiian Islands.
The surprise military strike by the Imperial Japanese Navy Air Service against the United States naval base led to the United States' formal entry into World War II.
Pearl Harbour also had a marked effect on the Manhattan Project. The S-1 Committee, which ran atomic research prior to the creation of the Manhattan Project, formally held its first meeting on December 18, 1941. This meeting initiated an official shift from the research to the development phase of the project, eventually leading to the deployment of the first nuclear weapons in combat.