Operation Coronet was the codename for the planned Allied invasion of Honshu under Operation Downfall.
Coronet was aimed at the Kantō Plain near Tokyo, Japan’s capital region. Planners tentatively scheduled the invasion for March 1, 1946, after an earlier operation called Olympic. Olympic was intended to seize southern Kyūshū in November 1945 and provide bases for the later assault on Honshu.
The plan was never carried out. Japan’s surrender in August 1945 followed the atomic bombings of Hiroshima and Nagasaki, the Soviet declaration of war, and the invasion of Japanese-held Manchuria. These events made the proposed invasion unnecessary.
Operation Coronet is often confused with Operation Olympic because both were components of Downfall. Operation Pastel was a proposed deception plan connected with Olympic, while Ketsugō was Japan’s defensive strategy for resisting an Allied invasion.