What was the planned Allied operation to invade Japan’s main island Honshu in 1946?

Operation Coronet was the planned Allied operation to invade Japan’s main island Honshu in 1946.

Coronet was the second phase of Operation Downfall, the proposed invasion plan for the Japanese home islands. It was intended to land Allied forces on the Kantō Plain near Tokyo, with a scheduled start date of March 1, 1946.

The first phase, Operation Olympic, was planned for November 1945 and targeted southern Kyushu. Coronet would have followed Olympic if Japan had not surrendered. Because both operations were canceled, no Allied invasion of the Japanese home islands took place.

Coronet is often confused with Downfall, which was the overall invasion plan, or Olympic, which concerned Kyushu specifically. Japan’s surrender after the atomic bombings, the Soviet entry into the Pacific War, and the resulting political and military pressure made the planned invasion unnecessary. The projected campaign would have been extraordinarily large and costly.