In May 1945, advance elements of First Army headquarters had returned to New York City and were preparing to redeploy to the Pacific theater of the war to prepare for Operation Coronet, the planned second phase of Operation Downfall the proposed invasion of Honshū, the main island of Japan in the spring of 1946, but the Japanese surrender in August 1945 thanks to the atomic bombings of Hiroshima and Nagasaki terminated that effort.