What was the planned second phase of the Allied invasion of Japan, scheduled for Honshu in 1946?

Operation Coronet was the planned second phase of the Allied invasion of Japan, scheduled for March 1, 1946. Its objective was the Kanto Plain on Honshu, the main Japanese island and the region containing Tokyo.

Coronet was part of Operation Downfall, the larger invasion plan developed in case Japan did not surrender. The first phase, Operation Olympic, was intended to seize southern Kyushu in November 1945. After securing Kyushu and building up forces, the Allies planned to land near Tokyo and advance across the Kanto Plain during Coronet.

The operation was canceled because Japan surrendered before Olympic began. Historians have debated the likely human cost of Downfall, but its exact casualties cannot be known because the invasion never occurred. Coronet should not be confused with Operation Olympic or with Operation Downfall itself: Olympic and Coronet were phases, while Downfall was the overall plan.