Operation Downfall was the codename for the
Allied plan for the invasion of
Japan near the end of
World War II. The planned operation was abandoned when
Japan surrendered following the
atomic bombings of
Hiroshima and
Nagasaki and the
Soviet declaration of war. The operation had two parts: Operations Olympic and Coronet. Set to begin in October 1945, Operation Olympic was intended to capture the southern third of the southernmost main Japanese island,
Kyushu, with the
recently captured island of
Okinawa to be used as a staging area. Later, in spring 1946, Operation Coronet was the planned invasion of the
Kanto Plain, near
Tokyo, on the Japanese island of
Honshu. Airbases on Kyushu captured in Operation Olympic would allow land-based air support for Operation Coronet. If Downfall had taken place, it would have been the largest amphibious operation in history.