What was the planned Allied invasion of Japan, considered before its 1945 surrender, called?

The planned Allied invasion of Japan was called Operation Downfall.

Operation Downfall was the proposed full-scale invasion of the Japanese home islands if Japan did not surrender. It had two main stages: Operation Olympic, the planned invasion of southern Kyushu, and Operation Coronet, the proposed assault on the Kantō Plain near Tokyo.

Olympic was scheduled for November 1945, while Coronet was planned for March 1946. Allied planners expected fierce resistance because Japan was preparing military units and civilians for a decisive defense of the homeland.

The atomic bombings of Hiroshima and Nagasaki, the Soviet declaration of war, and Japan’s decision to surrender made the invasion unnecessary. Operation Downfall was therefore never carried out, although planning documents and casualty estimates influenced wartime and postwar debates about the surrender.