Tornado Alley (PROG)

[blackhawks]

I'm sticking to unclear about what was in anyone's minds. That said.

An atomic attack on Japan, Truman thought, would preempt Soviet entry into the Pacific War and allow unilateral American occupation of Korea. His gamble failed. On August 8, Stalin declared war on Japan and sent the Red Army into Korea.

Were those the ONLY thoughts, the primary reasons, or.....?

https://en.wikipedia.org/wiki/Operation_Downfall#:~:text=Operation%20Downfall%20was%20the%20proposed,and%20the%20invasion%20of%20Manchuria.

Nuclear weapons

On Marshall's orders, Major General John E. Hull looked into the tactical use of nuclear weapons for the invasion of the Japanese home islands, even after the dropping of two strategic atomic bombs on Japan (Marshall did not think that the Japanese would capitulate immediately). Colonel Lyle E. Seeman reported that at least seven Fat Man-type plutonium implosion bombs would be available by X-Day, which could be dropped on defending forces. Seeman advised that American troops not enter an area hit by a bomb for "at least 48 hours"; the risk of nuclear fallout was not well understood, and such a short time after detonation would have exposed American troops to substantial radiation.[73]

Ken Nichols, the District Engineer of the Manhattan Engineer District, wrote that at the beginning of August 1945, "[p]lanning for the invasion of the main Japanese home islands had reached its final stages, and if the landings actually took place, we might supply about fifteen atomic bombs to support the troops."[74] An air burst 1,800–2,000 ft (550–610 m) above the ground had been chosen for the (Hiroshima) bomb to achieve maximum blast effects, and to minimize residual radiation on the ground, as it was hoped that American troops would soon occupy the city.[75]

Alternative targets

The Joint Staff planners, taking note of the extent to which the Japanese had concentrated on Kyushu at the expense of the rest of Japan, considered alternate places to invade such as the island of Shikoku, northern Honshu at Sendai, or Ominato. They also considered skipping the preliminary invasion and going directly at Tokyo.[76] Attacking northern Honshu would have the advantage of a much weaker defense but had the disadvantage of giving up land-based air support (except the B-29s) from Okinawa.[citation needed]

Prospects for Olympic
MacArthur dismissed any need to change his plans:

I am certain that the Japanese air potential reported to you as accumulating to counter our OLYMPIC operation is greatly exaggerated. … As to the movement of ground forces… I do not credit… the heavy strengths reported to you in southern Kyushu. … In my opinion, there should not be the slightest thought of changing the Olympic operation.[77]

However, King was prepared to oppose proceeding with the invasion, with Nimitz's concurrence, which would have set off a major dispute within the US government:

At this juncture, the key interaction would likely have been between Marshall and Truman. There is strong evidence that Marshall remained committed to an invasion as late as 15 August. … But tempering Marshall's personal commitment to invasion would have been his comprehension that civilian sanction in general, and Truman's in particular, was unlikely for a costly invasion that no longer enjoyed consensus support from the armed services.[78]

Soviet intentions
Main article: Proposed Soviet invasion of Hokkaido

In a proposed invasion plan, Soviet forces were to land at the remote port of Rumoi and occupy Hokkaido north of a line from Rumoi to Kushiro

Unknown to the Americans, the Soviet Union also considered invading a major Japanese island, Hokkaido, by the end of August 1945,[79] which would have put pressure on the Allies to act sooner than November.

In the early years of World War II, the Soviets had planned on building a huge navy to catch up with the Western world. However, the German invasion of the Soviet Union in June 1941 forced the suspension of this plan: the Soviets had to divert most of their resources to fighting the Germans and their allies, primarily on land, throughout most of the war, leaving their navy relatively poorly equipped.[80][81][82] As a result, in Project Hula (1945), the United States transferred about 100 naval vessels out of the 180 planned to the Soviet Union in preparation for the planned Soviet entry into the war against Japan. The transferred vessels included amphibious assault ships.

At the Yalta Conference (February 1945), the Allies had agreed that the Soviet Union would take the southern part of the island of Sakhalin, which Japan had invaded during the 1904–1905 Russo-Japanese War, and which Russia had ceded in the Treaty of Portsmouth after the war (the Soviets already controlled the northern part), and the Kuril Islands, which had been assigned to Japan in the 1875 Treaty of St. Petersburg. On the other hand, no agreement envisaged Soviet participation in the invasion of Japan itself.[citation needed]

What IS clear is that planning for the invasion of Japan began early in '45 and the estimate of casualties rose dramatically with the American casualties on Iwo Jima and Okinawa and the introduction of kamikazes in the latter invasion. All of those estimates were made without knowledge of the A-Bomb project.

The pressures to use the bomb in the hopes of avoiding those casualties had to be foremost in the minds of those who made the decision, if not in fact determinative.

Estimated casualties

Because the U.S. military planners assumed "that operations in this area will be opposed not only by the available organized military forces of the Empire, but also by a fanatically hostile population",[13] high casualties were thought to be inevitable, but nobody knew with certainty how high. Several estimates were made, but varied widely in numbers, assumptions and purposes, which included advocating and opposing the invasion. The estimated casualty figures later became a crucial point in postwar debate over the atomic bombings of Hiroshima and Nagasaki.

On 15 January 1945, the U.S. Army Service Forces released a document, "Redeployment of the United States Army after the Defeat of Germany." In it, they estimate that during the 18 month period after June 1945 (that is, through December 1946), the Army would be required to furnish replacements for 43,000 dead and evacuated wounded every month.[86] From analysis of the replacement schedule and projected strengths in overseas theaters, it suggested that Army losses alone in those categories, excluding the Navy and Marine Corps, would be approximately 863,000 through the first part of 1947, of whom 267,000 would be killed or missing.[87] This likewise excludes wounded who would be treated in-theater during an initial window of 30 days, later to be expanded to 120 days.

In preparation for Operation Olympic, the invasion of southern Kyushu, various figures and organizations made casualty estimates based on the terrain, strength, and disposition of known Japanese forces. However, as reported Japanese strength in the Home Islands continued to climb and Japanese military performance increased, so too did the casualty estimates.[88][page needed] In April 1945, the Joint Chiefs of Staff formally adopted a planning paper giving a range of possible casualties based on experience in both Europe and the Pacific.

These ranged from 0.42 dead and missing and 2.16 total casualties per 1000 men per day under the "European Experience" to 1.95 dead and missing and 7.45 total casualties per 1000 men per day under the "Pacific Experience."[89] This assessment included neither casualties suffered after the 90-day mark (US planners envisioned switching to the tactical defensive by X+120[90] ), nor personnel losses at sea from Japanese air attacks."[89] To sustain the campaign on Kyushu, planners estimated a replacement stream of 100,000 men per month would be necessary, a figure achievable even after the partial demobilization following the defeat of Germany.[88][page needed] As time went on, other US leaders made estimates of their own:

In a letter to General Curtis LeMay when LeMay assumed command of the B-29 force on Guam, General Lauris Norstad told LeMay that if an invasion took place, it would cost the US "half a million" dead.[91] In May, Admiral Nimitz's staff estimated 49,000 U.S casualties in the first 30 days of Operation Olympic, including 5,000 at sea.[92] A study done by General MacArthur's staff in June estimated 23,000 US casualties in the first 30 days of Olympic and 125,000 after 120 days, fighting an assumed Japanese force of 300,000[93] (in actuality some 917,000 Japanese troops were on Kyushu,[94]).

When these figures were questioned by General Marshall, MacArthur submitted a revised estimate of 105,000, in part by deducting wounded men able to return to duty.[95] In a conference with President Truman on June 18, Marshall, taking the Battle of 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 he estimated would include the entire Japanese force. This implied a total of 70,000 American casualties in the battle of Kyushu using the June projection of 350,000 Japanese defenders.[96]

Admiral Leahy, more impressed by the Battle of Okinawa, thought the American forces would suffer a 35% casualty rate (implying an ultimate toll of 268,000).[97] Admiral King thought that casualties in the first 30 days would fall between Luzon and Okinawa, i.e., between 31,000 and 41,000.[97] Of these estimates, only Nimitz's included losses of the forces at sea, though kamikazes had inflicted 1.78 fatalities and a similar number of wounded per kamikaze pilot in the Battle of Okinawa,[98] and troop transports off Kyushu would have been much more exposed.

In July MacArthur's Intelligence Chief, Maj. Gen. Charles A. Willoughby, warned of between 210,000 and 280,000 battle casualties in the push to the "stop line" one-third of the way up Kyushu. Even when rounded down to a conservative 200,000, this figure implied a total of nearly 500,000 all-causes losses, of whom perhaps 50,000 might return to duty after light to moderate care.[99] The US Sixth Army, the formation tasked with carrying out the major land fighting on Kyushu, estimated a figure of 394,859 casualties serious enough to be permanently removed from unit roll calls during the first 120 days on Kyushu, almost enough to outstrip the planned replacement stream.[100] Secretary of War Henry L. Stimson stated "We shall in my opinion have to go through an even more bitter finish fight than in Germany. We shall incur the losses incident to such a war and we shall leave the Japanese islands even more thoroughly destroyed than was the case with Germany."[101] From D-Day to V-E Day, the Western Allies alone suffered some 766,294 casualties.[102]

A study done for Stimson's staff by William Shockley estimated that invading 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.[3] Japanese military directives[which?][specify] ordered the execution of all POWs being held if Japan was ever invaded.[citation needed] Towards the end of the war about 100,000 Allied prisoners were in Japanese custody.[citation needed]

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 to 1,000,000 fatalities, which were believed to be conservative estimates; however, 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."[103]

The Battle of Okinawa was one of the bloodiest in the Pacific, with an estimated total of over 82,000 direct casualties on both sides: 14,009 Allied deaths and 77,417 Japanese soldiers.[104] Allied grave registration forces counted 110,071 dead bodies of Japanese soldiers, but this included conscripted Okinawans wearing Japanese uniforms.[105] 149,425 Okinawans were killed, committed suicide, or went missing, which was one-half of the estimated pre-war local population of 300,000.[104]

The battle resulted in 72,000 US casualties in 82 days, of whom 12,510 were killed or missing (this figure excludes the 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).[88][page needed]

In evaluating these estimates, especially those based on projected Japanese troop strength (such as General MacArthur's), it is important to consider what was known about the state of Japanese defenses at the time, as well as the actual condition of those defenses (MacArthur's staff believed Japanese manpower on Kyushu to be roughly 300,000).[106] Nearly 500,000 Purple Heart medals (awarded for combat casualties) were manufactured in anticipation of the casualties resulting from the invasion of Japan; the number exceeded that of all American military casualties of the 65 years following the end of World War II, including the Korean and Vietnam Wars. In 2003, there were still 120,000 of these Purple Heart medals in stock.[107] There were so many left that combat units in Iraq and Afghanistan could keep Purple Hearts on hand for immediate award to soldiers wounded in the field.[107]