What was the planned second phase of Operation Downfall, targeting the Tokyo Plain, called?

Operation Coronet was the planned second phase of Operation Downfall, targeting Japan’s Tokyo Plain.

Coronet was scheduled for March 1, 1946, after Operation Olympic’s planned invasion of Kyushu in November 1945. Its objective was the Kantō Plain on Honshu, the largest Japanese plain and the region containing Tokyo. The operation would have required a huge amphibious assault supported by extensive naval and air forces.

The plan was never carried out because Japan surrendered in August 1945. Operation Olympic therefore remained an unlaunched plan as well, despite detailed preparations for the invasion of Kyushu. The cancellation prevented the projected battles for the Japanese home islands and the expected casualties on both sides.

The name Coronet can be confused with Downfall, which described the entire invasion concept. It can also be confused with Olympic, which referred specifically to the Kyushu phase. Operation Neptune was the naval component of the Normandy invasion in 1944, not a plan for Japan.