What was the second planned phase of Operation Downfall, the proposed Allied invasion of Japan?

The second planned phase of Operation Downfall was Operation Coronet.

Operation Downfall was the proposed Allied invasion of Japan. Its first phase, Operation Olympic, was scheduled for Kyushu in November 1945. Operation Coronet would have followed in March 1946 with an invasion of Honshu, the main Japanese island, near the Kantō Plain.

The planned operations were never carried out because Japan surrendered in August 1945. Allied planners expected fierce resistance, drawing on the battles of Iwo Jima and Okinawa and Japan's preparations for homeland defense. The exact projected casualties varied by estimate and remain the subject of historical debate.

Coronet is sometimes confused with Olympic because both belonged to Downfall. Olympic concerned southern Kyushu; Coronet concerned the later assault on Honshu. The atomic bombings, Soviet entry into the war, Japan's internal political crisis, and the emperor's intervention ended the need for either invasion.