Which planned operation targeted the Kanto Plain near Tokyo in the proposed invasion of Japan?

Operation Coronet was the planned Allied invasion of the Kanto Plain near Tokyo.

Coronet was the second phase of Operation Downfall, the proposed invasion of Japan’s home islands. It was intended to follow Operation Olympic, which would have captured southern Kyushu and created bases for the next advance.

The Kanto Plain was selected because it contained Tokyo and offered the largest suitable area for a major invasion and buildup of forces. Coronet was tentatively scheduled to begin on March 1, 1946, after Olympic and the winter season.

Japan surrendered before either operation took place. Coronet is therefore a planned operation, not a battle. Its name is sometimes mistaken for Downfall, but Downfall was the overall invasion plan, while Olympic and Coronet were its two principal stages.