What was the code name for the planned Allied invasion of Japan in 1945?

Operation Downfall was the code name for the planned Allied invasion of Japan in 1945.

The plan was divided into two major phases. Operation Olympic was scheduled to begin in November 1945 with landings on Kyūshū, Japan’s southernmost main island. Operation Coronet was planned for March 1946 and would have targeted the Kantō Plain near Tokyo on Honshū. The invasion preparations reflected Allied expectations that Japan might continue fighting after the atomic bombings and the Soviet entry into the war.

Japan’s surrender meant that Downfall was never carried out. The plan is often confused with Operation Overlord, the Allied invasion of German-occupied France in June 1944. Downfall belonged to the Pacific theater and was aimed at the Japanese home islands. Its projected scale helps explain why the end of the war in August and September 1945 was treated as a major turning point: it canceled an invasion that would have required enormous forces and produced potentially severe casualties.