What was the planned second stage of Operation Downfall, aimed at the Kantō Plain?

Operation Coronet was the planned second stage of Operation Downfall, aimed at Japan's Kantō Plain.

The Kantō Plain surrounds Tokyo on the island of Honshū, Japan's largest and most populous main island. Coronet was intended to follow Operation Olympic, the planned invasion of southern Kyūshū. Airfields captured during Olympic would have helped provide support for the advance toward the Tokyo region.

Coronet was planned for spring 1946 and was expected to be larger than Olympic. The Downfall plan called for enormous troop, vehicle, shipping, and air requirements, reflecting the Allies' expectation that Japan would defend its home territory with maximum effort.

Japan's surrender in August 1945 canceled both stages. Coronet should not be confused with Operation Overlord, the Allied campaign in Normandy, or Operation Avalanche, the 1943 invasion of mainland Italy. Those operations belonged to the European and Mediterranean theaters, not the planned invasion of Japan.