Which Operation Downfall phase planned an assault on the Kantō Plain near Tokyo?

Operation Coronet was the Operation Downfall phase planned to assault the Kantō Plain near Tokyo.

Coronet was scheduled for spring 1946, after the planned invasion and consolidation of southern Kyūshū under Operation Olympic. The Kantō Plain was strategically important because it contained Tokyo and much of Japan’s political and industrial infrastructure.

Planning envisioned Allied armies landing on beaches near the Bōsō Peninsula and Sagami Bay before advancing toward Tokyo. Coronet was expected to be even larger than Olympic and among the largest amphibious operations ever planned.

The surrender of Japan in August 1945 made the invasion unnecessary, so Coronet was never executed. It is often confused with Olympic because both were components of Downfall. Olympic concerned Kyūshū; Coronet concerned the Kantō Plain and the capital region on Honshū.