Here's the casualty calculus if it may help....
Estimated casualties for Downfall
Given the Japanese predilection for fanatical resistance, the fact that Japanese civilians were being encouraged to become suicide attackers, and the large number of Japanese troops to be faced, high casualties were seen to be inevitable, but nobody knew with certainty how high. Several people made estimates but they varied widely in numbers, assumptions, and purposes—which included advocating for and against the invasion—afterwards, they were reused to argue for and against the atomic bombings of Hiroshima and Nagasaki.
Everybody based their estimates on the experience of the preceding campaigns, but they could draw different lessons:
In a study done by the Joint Chiefs of Staff in April, the figures of 7.45 casualties/1000 man-days and 1.78 fatalities/1000 man-days were developed. This implied 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.
A study done by Adm. Nimitz's staff in May estimated 49,000 casualties in the first 30 days, including 5,000 at sea. A study done by Gen. MacArthur's staff in June estimated 23,000 in the first 30 days and 125,000 after 120 days. When these figures were questioned by Gen. Marshall, MacArthur submitted a revised estimate of 105,000, in part by deducting wounded men able to return to duty.
In a conference with President Truman on 18 June, Marshall, taking Luzon as the best model for Olympic, thought the Americans would suffer 31,000 casualties in the first 30 days (and ultimately 20% of Japanese casualties, which implied a total of 70,000 casualties). Adm. Leahy, more impressed by Okinawa, thought the American forces would suffer a 35% casualty rate (implying an ultimate toll of 268,000). Admiral King thought that casualties in the first 30 days would fall between Luzon and Okinawa, i.e., between 31,000 and 41,000.
Of these estimates, only Nimitz's included losses of the forces at sea, though in the Battle of Okinawa kamikazes had inflicted 1.78 fatalities per kamikaze pilot, and the troop transports off Kyushu would be much more exposed.
A study done for Secretary of War Henry Stimson's staff by William Shockley 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.
Outside the government, well-informed civilians were also making guesses. Kyle Palmer, war correspondent for the Los Angeles Times, said half a million to a million Americans would die by the end of the war. Herbert Hoover, in memorandums submitted to Truman and Stimson, also estimated 500,000–1,000,000 fatalities, and were believed to be conservative estimates; but it is not known if Hoover discussed these specific figures in his meetings with Truman. The chief of the Army Operations division thought them "entirely too high" under "our present plan of campaign."
For context, the Battle of Normandy had cost 63,000 casualties in the first 48 days. The Battle of Okinawa caused 72,000 casualties, of whom 18,900 were killed or missing over about 82 days. Several thousand soldiers who died indirectly whether because of wounds or other causes at a later date are not included. The entire war cost the United States a total of just over a million casualties, with 400,000 fatalities.
Nearly 500,000 Purple Heart medals were manufactured in anticipation of the casualties resulting from the invasion of Japan. As of 2005, all the American military casualties of the following sixty years—including the Korean and Vietnam Wars—have not exhausted that stockpile. [1] This is somewhat misleading, however, as it suggests that Purple Hearts being issued currently are those minted in the closing days of World War II. In actual fact, the design of the medal and it's corresponding service ribbon have been updated since the end of the Korean war, so the surplus ones represent an obsolete design that is no longer awarded.
It is important to remember that the casualty estimates are just that, and that they do not take into account the demoralizing effect the incessant air attacks had on the Japanese population. For example, in early August Fifth Air Force fighter pilots came back from low altitude missions over Kyushu to report that white flags were flying in towns and villages all over the island. Post-war interrogations revealed that almost 70% of the Japanese population had reached the point that they felt they were unable to endure one more day of war.
Linkie:
http://en.wikipedia.org/wiki/Operation_Downfall
