What was the Allied plan for invading Japan that was never carried out in 1945?

Operation Downfall was the Allied plan for invading Japan that was never carried out in 1945.

The proposed operation was divided into two major stages. Operation Olympic would have invaded Kyūshū, Japan’s southernmost main island, in November 1945. Operation Coronet would then have targeted the Kantō Plain near Tokyo in March 1946. Together, these operations were known as Operation Downfall.

Planning reflected Allied expectations that Japan might continue fighting despite its worsening military position. The projected invasion promised enormous casualties on both sides, although estimates varied and remain debated by historians. The atomic bombings of Hiroshima and Nagasaki, the Soviet entry into the war against Japan, and Japan’s decision to surrender made the planned invasion unnecessary.

Operation Downfall is often confused with Olympic or Coronet. Those were component operations, while Downfall was the overall invasion plan. Because the invasion never happened, it remains a counterfactual military operation rather than a campaign conducted in the Pacific.