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

The planned second stage of Operation Downfall was called Operation Coronet.

Coronet was intended to invade the Kanto Plain on Japan’s main island, Honshu, near Tokyo. Allied planners expected it to follow Operation Olympic, the proposed November 1945 invasion of southern Kyushu. Coronet was projected for spring 1946.

The Kanto Plain was strategically important because it contained Tokyo and surrounding population, transportation, and industrial centers. Captured bases in Kyushu from Olympic would have helped provide air support for Coronet.

Japan’s surrender in August 1945 made both planned operations unnecessary. Coronet therefore belongs to the history of proposed operations rather than completed combat. It is sometimes mistakenly described as an actual battle or landing, but Allied troops never launched it.