The surrender of Imperial Japan was announced on August 15 and formally signed on September 2, 1945, bringing the hostilities of World War II to a close. Some believe the Aug. 15, 1945, declaration was the result of the atomic bombs dropped on Hiroshima and Nagasaki.By the end of July 1945, the Imperial Japanese Navy (IJN) was incapable of conducting major operations and an Allied invasion of Japan was imminent.