What was the Allied plan for invading the Japanese home islands if Japan did not surrender?

Operation Downfall was the Allied plan for invading the Japanese home islands if Japan did not surrender.

The plan was divided into two major stages. Operation Olympic would have invaded southern Kyushu, while Operation Coronet would have targeted the Kanto Plain near Tokyo. Olympic was scheduled for November 1945, with Coronet planned for March 1946.

Downfall was never carried out because Japan accepted the Potsdam Declaration in August 1945 and signed its surrender in September. Allied planners expected an invasion to be extremely costly because Japanese forces were preparing for a decisive defense of the home islands and civilians were being trained for resistance.

Operation Downfall is sometimes confused with Operation Olympic or Operation Coronet. Downfall was the overall invasion plan; Olympic and Coronet were its two component operations. The planned invasion became part of later debates about the reasons for using atomic bombs and the Soviet entry into the war.