What was the codename for the proposed Allied invasion of Japan’s home islands in 1945?

Operation Downfall was the codename for the proposed Allied invasion of Japan’s home islands in 1945.

Downfall was planned as a two-stage operation. Operation Olympic would have invaded southern Kyushu in November 1945, while Operation Coronet would have attacked the Kantō Plain near Tokyo in spring 1946.

The plan was canceled after Japan accepted the Potsdam Declaration and surrendered. The atomic bombings of Hiroshima and Nagasaki, the Soviet declaration of war, and the invasion of Manchuria all contributed to the changed strategic situation.

Operation Downfall is often discussed because planners expected an enormous and costly campaign. If carried out, it would have required hundreds of thousands of personnel and potentially become the largest amphibious operation in history, surpassing the Normandy landings.