Operation Downfall was the planned Allied invasion of Japan that was cancelled after Japan surrendered.
The plan was divided into two major operations. Operation Olympic was the proposed invasion of Kyūshū, scheduled for November 1945, while Operation Coronet was the proposed assault on Honshū near Tokyo, planned for March 1946. Together, these operations formed Operation Downfall.
Downfall never took place because Japan accepted the Allied surrender terms in August 1945. The plan nevertheless shaped Allied preparations in the final months of the war. American planners anticipated fierce resistance based on the fighting at Iwo Jima and Okinawa, as well as Japan’s preparations for homeland defense.
Operation Downfall is often confused with Operation Overlord, the Allied invasion of Nazi-occupied Normandy in June 1944. Downfall concerned Japan; Overlord concerned the European theater. The cancellation avoided a planned invasion but did not end all fighting immediately, since surrender documents were signed on 2 September.