What was the overall Allied invasion plan for mainland Japan that was canceled after Japan surrendered?

Operation Downfall was the overall Allied invasion plan for mainland Japan that was canceled after Japan surrendered.

Downfall had two major components. Operation Olympic was scheduled to begin in November 1945 with an invasion of southern Kyūshū. Operation Coronet was planned for spring 1946 and would have attacked the Kantō Plain near Tokyo on Honshū.

The plan was abandoned after Japan accepted surrender terms in August 1945. The atomic bombings of Hiroshima and Nagasaki, the Soviet entry into the war against Japan, and Japan’s political decision to surrender all occurred before the planned invasion dates.

Operation Downfall is sometimes confused with its two component operations. Olympic referred to the Kyūshū assault, while Coronet referred to the later Honshū operation. If carried out, Downfall would have been one of history’s largest amphibious campaigns, requiring massive troop movements and facing preparations by Japan for an all-out defense of the home islands.