What Allied invasion plan was prepared for a possible invasion of Japan in 1945?

Operation Downfall was the Allied plan for a possible invasion of Japan in 1945.

The plan consisted of two major stages. Operation Olympic called for an invasion of southern Kyushu, scheduled for November 1945, while Operation Coronet was planned for an assault on Honshu near Tokyo in March 1946.

Downfall was never carried out because Japan surrendered in August 1945. Allied planners expected fierce resistance, based partly on the fighting at Iwo Jima and Okinawa and Japan’s preparations for a homeland defense. Estimates of potential casualties varied widely and remain historically disputed.

The atomic bombings of Hiroshima and Nagasaki, the Soviet declaration of war, and Japan’s internal surrender decision ended the need for the invasion. Operation Downfall is therefore an example of a major military plan that remained unexecuted rather than a campaign that began.