What was the overall Allied invasion plan for Japan if it had not surrendered?

Operation Downfall was the overall Allied invasion plan for Japan if it had not surrendered.

The plan was divided into two major operations. Operation Olympic was intended to land on Kyushu in November 1945, while Operation Coronet was planned for the Tokyo Plain on Honshu in March 1946. Downfall therefore describes the complete invasion concept rather than either phase alone.

The planned campaign was abandoned after Japan accepted the surrender terms in August 1945. The atomic bombings, the Soviet declaration of war and invasion, Japan’s internal political crisis, and the prospect of enormous casualties all formed part of the final surrender context.

Operation Downfall is often confused with Operation Olympic because Olympic was the first scheduled stage. It is also unrelated to Operation Overlord, the Allied invasion of Nazi-occupied France in June 1944. Downfall was never carried out, so its projected casualties and exact course remain matters of historical analysis rather than battlefield results.