What was the planned Allied invasion of Japan called during World War II?

The planned Allied invasion of Japan was called Operation Downfall. It was canceled after Japan surrendered in August 1945, before the invasion could begin.

Downfall consisted of two proposed stages. Operation Olympic was scheduled for November 1945 and would have targeted southern Kyūshū. Operation Coronet was planned for spring 1946 and would have attacked the Kantō Plain near Tokyo on Honshū.

The projected invasion was expected to be extremely costly because Japan was preparing for a decisive defense of its home islands. The Allies had already experienced heavy fighting on Iwo Jima and Okinawa, while Japanese military planners prepared civilian and military resistance for a home-island invasion. Japan's surrender, influenced by the atomic bombings and the Soviet declaration of war, made Downfall unnecessary.