Operation Coronet was the planned second stage of the Allied invasion of Japan, aimed at the Kantō Plain.
Coronet was scheduled for March 1, 1946, after Operation Olympic had established a foothold on southern Kyūshū. Its objective was the Kantō Plain on Honshu, the main Japanese island, including the area around Tokyo. The plan formed the second half of the larger Operation Downfall.
Coronet was expected to be even larger than Olympic because it would have required a major concentration of troops and supplies near Japan’s political and industrial center. Planning called for U.S. forces to land near the Kantō Plain, with Commonwealth participation also considered during the later planning stages.
Coronet was never launched. Japan’s surrender in August 1945 followed the atomic bombings and the Soviet entry into the war. Operation Ketsugō was Japan’s defensive response plan, not the Allied invasion itself.