Operation Downfall

Operation DOWNFALL was the overall planning U.S. planning term for the invasion of the home islands of Japan, should forcible entry and ground combat be necessary. Air, naval, and submarine operations, including the nuclear attacks on Hiroshima and Nagasaki, led to a Japanese surrender, making DOWNFALL unnecessary.

DOWNFALL had two main subsidiary operations, Operation OLYMPIC against the southern island of Kyushu, and Operation CORONET, which would move against the Kanto Plain containing Tokyo. Only a few DOWNFALL planners were aware of the Manhattan Project, the U.S. nuclear weapons development program, but plans were evolving to use nuclear weapons in tactical support.