What code name did the United States use for its planned invasion of Japan’s home islands?

Operation Downfall was the code name for the planned United States invasion of Japan’s home islands. It was never carried out because Japan surrendered before the invasion began.

The plan had two major stages. Operation Olympic was intended to land on southern Kyushu on November 1, 1945, while Operation Coronet was planned for the Kanto Plain near Tokyo on March 1, 1946. Together, these operations formed Downfall and envisioned a massive Allied campaign against Japan.

Planning for Downfall reflected Allied expectations that Japan might continue fighting despite increasingly severe military pressure. The atomic bombings, the Soviet declaration of war, Japan’s internal political crisis, and the emperor’s decision changed the situation before Olympic could begin. Operation Downfall is therefore often mentioned in discussions of the war’s ending, but it was a plan rather than an executed battle. Operation Olympic and Operation Coronet were its component phases, not alternative names for the entire plan.