Which phase of Operation Downfall was planned to attack the Kanto Plain near Tokyo?

Operation Coronet was the phase of Operation Downfall planned to attack the Kanto Plain near Tokyo.

Coronet was intended to follow Operation Olympic, the planned invasion of southern Kyushu. The target area on Honshu included the Kanto Plain, the broad region surrounding Tokyo. The operation was tentatively scheduled for March 1946 after Allied forces had secured bases and positions through Olympic.

The planned assault would have involved the U.S. First and Eighth Armies, with additional Allied support. It was expected to be larger than Olympic because capturing the Tokyo region was central to defeating Japan’s remaining government and military leadership.

Coronet never took place. Japan surrendered before either phase of Downfall began. Operation Ketsugo was the Japanese defensive plan for the expected invasion, making it a separate operation rather than an Allied phase of Downfall.