"we shall probably have to kill at least 5 to 10 million Japanese. This might cost us between 1.7 and 4 million casualties including 400,000 to 800,000 killed"
In July 1945, the War Department asked Shockley to prepare a report on the question of probable casualties from an invasion of the Japanese mainland. This report influenced the decision for the atomic bombings of Hiroshima and Nagasaki to force Japan to surrender without an invasion. The key assumption was large-scale participation by civilians in the defense of Japan.