Operation Downfall was the Allied plan for invading the Japanese home islands in 1945.
Downfall was a proposed United States and British Empire operation that would have begun after Japan refused to surrender. It had two major phases. Operation Olympic was scheduled for November 1, 1945, and would have attacked southern Kyushu. Operation Coronet was planned for spring 1946 against the Kanto Plain near Tokyo.
The plan was canceled after Japan accepted surrender terms following the atomic bombings of Hiroshima and Nagasaki and the Soviet entry into the war against Japan. Had it occurred, Downfall would have been the largest amphibious operation in history, exceeding the scale of the Normandy landings.
Operation Downfall is often confused with its component operations. Olympic and Coronet were not alternative names for the entire invasion plan; they were the two principal stages within Downfall. Operation Overlord, by contrast, was the Allied invasion of German-occupied Western Europe in 1944.