What was the name of the planned Allied invasion of Japan's home islands in 1945–46?

The planned Allied invasion of Japan's home islands in 1945–46 was called Operation Downfall.

Downfall was the overall plan for a direct invasion if Japan did not surrender. It had two principal stages: Operation Olympic, aimed at southern Kyushu, and Operation Coronet, aimed at the Kanto Plain near Tokyo on Honshu.

Olympic was scheduled for November 1945, while Coronet was planned for early 1946. The invasion would have required enormous numbers of troops, ships, aircraft, and landing craft. American planners expected fierce resistance from Japanese military forces and civilians prepared for homeland defense.

Japan's surrender made Downfall unnecessary. The decision followed the atomic bombings of Hiroshima and Nagasaki, the Soviet Union's entry into the war against Japan, and intense political debate within Japan. Because the invasion never occurred, casualty estimates for Downfall remain projections rather than actual battlefield totals.