Hiroshima - quit lying to yourselves

[Dollface]

238. My dad was also a Marine preparing for the invasion of Japan. Casualty estimates were high.

Casualty estimates were based on the experience of the preceding campaigns, drawing different lessons:

In a letter sent to Gen. Curtis LeMay from Gen. Lauris Norstad, when LeMay assumed command of the B-29 force on Guam, Norstad told LeMay that if an invasion took place, it would cost the US "half a million" dead.

In a study done by the Joint Chiefs of Staff in April, it was estimated that a 90-day Olympic campaign would cost 456,000 casualties, including 109,000 dead or missing. If Coronet took another 90 days, the combined cost would be 1,200,000 casualties, with 267,000 fatalities. (Operation Olympic, the invasion of Kyūshū, was scheduled for November 1, 1945. Fourteen US divisions were scheduled to take part in the initial landings. The objective would have been to seize the southern portion of Kyūshū. This area would then be used as a further staging point to attack Honshū in Operation Coronet.)

A study done for Secretary of War Henry Stimson estimated that conquering Japan would cost 1.7–4 million American casualties, including 400,000–800,000 fatalities, and five to ten million Japanese fatalities. The key assumption was large-scale participation by civilians in the defense of Japan.

The Battle of Okinawa ran up 72,000 US casualties in 82 days, of whom 12,510 were killed or missing (this is conservative, because it excludes several thousand US soldiers who died after the battle indirectly, from their wounds.) The entire island of Okinawa is 464 sq mi (1,200 km2). If the US casualty rate during the invasion of Japan had been only 5% as high per unit area as it was at Okinawa, the US would still have lost 297,000 soldiers (killed or missing).

So best case was about a million dead. Worst case was 14 million. Mr. Truman didn't have the benefit of hindsight.