What was the Allied plan to invade Japan's home islands in World War II called?

The Allied plan to invade Japan’s home islands in World War II was called Operation Downfall.

Downfall was a proposed United States and British Empire operation for defeating Japan through a direct invasion. It was divided into two major phases: Operation Olympic, aimed at southern Kyūshū, and Operation Coronet, aimed at the Kantō Plain near Tokyo.

Olympic was scheduled for November 1, 1945, while Coronet was planned for spring 1946. The invasion would have required enormous numbers of troops, ships, aircraft, and supplies. Allied planners expected severe casualties, and Japanese leaders prepared their own defensive plans for a homeland battle.

Downfall was canceled after Japan accepted the Allied surrender terms. The atomic bombings of Hiroshima and Nagasaki, the Soviet entry into the war against Japan, and the resulting surrender made the planned invasion unnecessary. Operation Downfall is often confused with Operation Overlord, the Allied invasion of Normandy in 1944.