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President Truman and the Atom Bomb Decision: “Preventing an Okinawa from One End of Japan to Another”

What did President Harry S. Truman and his senior advisers believe an invasion of Japan would cost in American dead? For many years this has been a matter of heated historical controversy, with Truman's critics maintaining that the huge casualty estimates he later cited were a "postwar creation" designed to justify his use of nuclear weapons against a beaten nation already on the verge of suing for peace. The real reasons, they maintain, range from a desire to intimidate the Russians to sheer bloodlust. One historian wrote in the New York Times: "No scholar of the war has ever found archival evidence to substantiate claims that Truman expected anything close to a million casualties, or even that such large numbers were conceivable." Another skeptic insisted on the total absence of "any high-level supporting archival documents from the Truman administration in the months before Hiroshima that, in unalloyed form, provides even an explicit estimate of 500,000 casualties, let alone a million or more."

A series of documents discovered at the Harry S. Truman Presidential Library and Museum in Independence, Missouri, and described by this author in an article in the Pacific Historical Review, tell a different story.

In the midst of the bloody fighting on Okinawa, which began in April 1945, President Truman received a warning that the invasion could cost as many as 500,000 to 1,000,000 American lives. The document containing this estimate, "Memorandum on Ending the Japanese War," was one of a series of papers written by former President Herbert Hoover at Truman's request in May 1945.

The Hoover memorandum is well known to students of the era, but they have generally assumed that Truman solicited it purely as a courtesy to Hoover and Secretary of War Henry Stimson, who had been Hoover's Secretary of State. What had lain buried in the Truman Library archives, however, was Harry Truman’s reaction to Hoover’s memoranda and the “Truman-Grew-Hull-Stimson-Vinson exchange” that it prompted.

Truman reviewed the material from the former president and after writing “From Herbert Hoover” across the top of its memo 4, “Memorandum on Ending the Japanese War,” he forwarded the original copy to his manpower czar, Fred M. Vinson on or about Monday, June 4. The War Mobilization and Reconversion director had no quarrel with the casualty estimate when he responded on Thursday, 7 June, suggesting that Hoover’s paper be sent to Secretary Stimson and Acting Secretary of State Joseph C. Grew, as well as former Secretary of State Cordell Hull, who was currently a patient at the Bethesda Naval Medical Center.

Truman agreed and had his staff type up additional copies of memo 4 on Saturday, June 9 and sent them to Stimson, Grew, and Hull asking each for a written analysis and telling both Grew and Stimson that he wished to discuss their individual analyses personally — eye to eye — after they submitted their responses. Stimson subsequently sent his copy to the Deputy Chief of Staff, Major General Thomas J. Handy because he wanted to get “the reaction of the Operations Division Staff to it” and mentioned in his diary that he “had a talk both with Handy and [General George C.] Marshall on the subject.” Handy's staff then produced a briefing paper for Stimson which drew attention to the fact that memo 4's figure of potentially 1,000,000 American dead was fully double the Army's estimates.  It was “entirely too high under the present plan of campaign” which entailed only the seizure of southern Kyushu, the Tokyo region, and several key coastal areas.  The pointed disclaimer “under the present plan of campaign” was, however, literally the only part of the 550-word analysis, excluding headlines, that carried a typed underline and was an ominous reminder that the battle then raging on Okinawa was itself not playing out as planned.

Hull was the first to respond directly to Truman. He branded memo 4 Hoover’s “appeasement proposal” in his June 12 letter because it suggested that the Japanese be offered lenient terms to entice them to a negotiating table. Hull did not take issue with the casualty estimate. Grew also did not take issue with the casualty estimate in his June 13 memorandum and confirmed that the Japanese “are prepared for prolonged resistance” and that “prolongation of the war will cost a large number of human lives.”

Grew’s opinion would not have come as any surprise to the president since he had told Truman, ironically just hours after the meeting with Hoover, that “The Japanese are a fanatical people capable of fighting to the last man. If they do this, the cost in American lives will be unpredictable.” One can readily surmise that Hoover and Grew’s statements, hitting virtually back-to-back in the midst of America’s costliest campaign of the Pacific war on Okinawa, were not of much comfort to the new commander in chief.

Grew’s memorandum, messengered by government courier, and Hull’s letter both arrived on Wednesday, June 13, and Truman subsequently met with Admiral William D. Leahy on the matter. Leahy, who was the president’s personal representative on the Joint Chiefs of Staff and acted as unofficial chairman at their meetings, sent a memorandum, stamped “URGENT” in capital letters, to the other JCS members as well as Secretary of War Stimson and Secretary of the Navy James Forrestal. The president wanted a meeting the following Monday afternoon, June 18, 1945, to discuss, “the losses in dead and wounded that will result from an invasion of Japan proper,” and Leahy stated unequivocally that “It is his intention to make his decision on the campaign with the purpose of economizing to the maximum extent possible in the loss of American lives. Economy in the use of time and in money cost is comparatively unimportant.” The night before the momentous meeting, Truman wrote in his diary that the decision whether to “invade Japan [or] bomb and blockade” would be his “hardest decision to date.”

The “Truman-Grew-Hull-Stimson-Vinson exchange” not only places the very high casualty numbers squarely on the President's desk long before Hiroshima, but, says Robert Ferrell, editor of Truman's private papers, it demonstrates that Truman "was exercised about the 500,000 figure, no doubt about that." Ferrell adds that the exchange answers the question of why Truman called the June 18 meeting with the Joint Chiefs, Navy Secretary Forrestal, and Stimson. Said the senior archivist at the Truman Library, Dennis Bilger, when shown the documents: "This is as close to a one-to-one relationship as I have ever seen in the historical record." Yet another discovery, by the Hoover Presidential Library's former senior archivist, Dwight M. Miller, indicates that the huge casualty estimate likely originated during Hoover's regular briefings by Pentagon intelligence officers.

The possible cost in American blood was of paramount importance. Entering the war “late” –and because of its sheer distance from Europe and the western Pacific – the United States did not begin to experience casualties comparable to those of the other belligerents until the conflict’s final year. By then the U.S. Army alone was losing soldiers at a rate that Americans today would find astounding, suffering an average of 65,000 killed, wounded, and missing each and every month during the “casualty surge” of 1944-45, with the November, December, and January figures standing at 72,000, 88,000 and 79,000 respectively in postwar tabulations.

Most of these young men were lost battling the Nazis, but Truman was greatly disturbed by the casualty figures from the ongoing Okinawa Campaign and the Marines’ recent battle on Iwo Jima. Even though the United States was by now several months into the steep increase in draft calls implemented under President Franklin D. Roosevelt to produce a 140,000-men-per-month “replacement stream” for the now one-front war, Truman wanted to directly address this matter with his most senior advisors.

The president’s meeting with the Joint Chiefs and service secretaries took place before one of the recipients of Truman directive, Stimson, had submitted a written response. It was not until after the meeting and several drafts that Stimson wrote: “The terrain, much of which I have visited several times, has left the impression on my memory of being one which would be susceptible to a last ditch defense such as has been made on Iwo Jima and Okinawa and which of course is very much larger than either of those two areas. . . . We shall in my opinion have to go through a more bitter finish fight than in Germany [and] we shall incur the losses incident to such a war.”

At the Monday meeting, all the participants agreed that an invasion of the Home Islands would be extremely costly, but that it was essential for the defeat of Imperial Japan. Said Marshall: “It is a grim fact that there is not an easy, bloodless way to victory.” There was also considerable discussion of the tactical and operational aspects surrounding the opening invasion of Kyushu, the southernmost of Japan’s Home Islands, with the emphasis on their effects on American casualties. The meeting transcript says that: “Admiral Leahy recalled that the President had been interested in knowing what the price in casualties for Kyushu would be and whether or not that price could be paid. He pointed out that the troops on Okinawa had lost 35 percent in casualties.”

Leahy noted that “If this percentage were applied to the number of troops to be employed in Kyushu, he thought from the similarity of the fighting to be expected, that this would give a good estimate of the casualties to be expected. He was interested therefore in finding out how many troops are to be used in Kyushu.”

Leahy did not believe that the dated and narrowly constructed figure of 34,000 ground force battle casualties in a ratio table accompanying General Marshal’s opening presentation offered a true picture of losses on Okinawa which, depending on the accounting method used, actually ran from 65,631 to 72,000 partially because of extreme exhaustion and combat-related psychosis. He used the total number of Army-Marine casualties to formulate the 35 percent figure, a figure which excluded the U.S. Navy’s brutal losses to Japanese Kamikaze suicide aircraft. Since Leahy, as well as the other participants including Truman, already knew that ground force casualties on Okinawa were far higher than 34,000 and approximately how many men were to be committed to the Kyushu fight, he was obviously making an effort — commonly done in such meetings — to focus the participants’ attention on the statistical consequences of the disparity. General Marshall presented the most recent figure for the troop commitment in this first (and smaller) operation of the two-phase invasion, 766,700, and allowed those around the table, including Leahy, to draw their own conclusions as to long-term implications.

A discussion then ensued on the sizes of the opposing Japanese and American forces which was fundamental to understanding how Leahy’s 35 percent might play out. Finally, Truman, who was continuing to monitor the rising casualty figures from Okinawa on a daily basis cut to the bottom line since the initial assault, Operation Olympic against the Island of Kyushu, would in fact be dwarfed by the Spring 1946 strike directly at Tokyo, Operation Coronet: “The President expressed the view that it was practically creating another Okinawa“ to which “the Chiefs of Staff agreed.”

More discussion ensued and Truman asked “if the invasion of Japan by white men would not have the effect of more closely uniting the Japanese?” Stimson stated that “there was every prospect of this.” He added that he “agreed with the plan proposed by the Joint Chiefs of Staff as being the best thing to do, but he still hoped for some fruitful accomplishment through other means.” The “other means” included a range of measures from increased political pressure brought to bear through a display of Allied unanimity at the upcoming conference in Potsdam to the as yet untested atomic weapons that it was hoped would “shock” the Japanese into surrender.

Continued discussion touched on military considerations and the merits of unconditional surrender, and the president moved to wrap up the meeting: “The President reiterated that his main reason for this conference with the Chiefs of Staff was his desire to know definitely how far we could afford to go in the Japanese campaign. He was clear on the situation now and was quite sure that the Joint Chiefs of Staff should proceed with the Kyushu operation” and expressed the hope that “there was a possibility of preventing an Okinawa from one end of Japan to the other.”

Other HNN articles by D. M. Giangreco relating to President Harry S. Truman’s decision to drop the atomic bomb: