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Was Dwindling US Army Manpower a Factor in the Atom Bombing of Hiroshima?

The US Army had been grappling with the question of how to man its rapidly expanding force even before Pearl Harbor.   This was an increasingly critical, though largely unknown, problem throughout the war.   In the midst of a partial demobilization after the defeat of Nazi Germany, the Army called together some of its sharpest minds to examine the deteriorating situation as it geared up for the planned invasions of Japan in 1945 and 1946.   One of those men was Dr. Michael DeBakey, who died last week at the age of 99. The group also included figures such as Dean Rusk and future Nobel laureate  Dr. William B. Shockley.

Analyses conducted during the early 1940s suggested that the number of Americans appropriately aged and physically fit for military service was approximately 25,000,000, and it was anticipated that industrial and agricultural needs would cut this figure down by as many as 10,000,000.   The Army originally, and optimistically, planned to raise 200 combat divisions of all types, but it didn't take long for the realities of production and Army Air Force requirements to be fully appreciated.   By 1943 the number of such formations was scaled back considerably, and eventually shrank to a planned 90 divisions.

In May 1944, Secretary of War Henry Stimson repeatedly fretted over the lack of troops being committed to the upcoming invasion of France.   He pushed hard for a greater share of the Army's limited manpower to be allotted to the formation of additional combat divisions, but the Army's senior leadership was just as adamant that the lack of soldiers--- and especially officers--- made it impossible to efficiently support more divisions.   They argued that the greatest asset the United States brought to the Allied coalition was its immense production capacity.

Stimson, fearing a possible stalemate on the Western Front, complained in his diary and to aides that Army Chief of Staff George C. Marshall "takes quite a different view--- a more optimistic view on some things that I think are rather dangerous," yet he did not raise his concerns with President Roosevelt because he did not want "to make an appearance of an issue with Marshall" with whom he was in fundamental agreement on so many issues.  

As events during the German's Ardennes Offensive later proved, Stimson had been at least partially correct and, by May 1945, he was again concerned with the casualties question, this time for the invasion of Japan.   But instead of grudgingly deferring to Marshall and the Army leadership, he specifically wanted civilian personnel not connected to Army Ground Forces, or AGF,  to be called in for a reexamination of manpower "requirements" for what he and Marshall both agreed would be a more brutal slugfest than the war in Europe largely because of the terrain and the character of the Japanese soldier.

It is instructive to take a look at the casualties between Stimson's memos to Marshall on May 10 and 16, 1944, and his June 9, 1945, initiation of a top-level review of the replacement system.

The long-expected “casualty surge”--- that all had known was coming --- finally arrived in the summer of 1944 with D-Day in France and the invasion of the Mariana Islands in the Pacific.   Of America’s roughly one and a quarter million combat and combat-related casualties in World War II, nearly one million of this number would be suffered from June 1944 through June 1945, a number that Americans today understandably would find almost incomprehensible.

The US Army was suffering an average of 65,000 combat casualties each and every month during the casualty surge, with November, December, and January figures standing at 72,000, 88,000 and 79,000 respectively in postwar tabulations.   The heavy American casualties during the Ardennes offensive, and lack of US combat divisions to add weight to Allied counterattacks, spurred Stimson to press more forcefully to create additional combat formations in the European Theater--- and Marshall remained just as firm that this could not be done without creating immense manpower disruptions.

Marshall had successfully rebuffed Stimson for almost a year on this, but in the crisis atmosphere of the current emergency, "head-on fight[s]" (that's Stimson's description) erupted between Stimson, Marshall, and Marshall's Deputy Chief of Staff, Major General Thomas Handy.   The compromise solution was to send the last nine uncommitted divisions across the Atlantic by mid February including two that had been trained specifically for the invasion of Japan.  Meanwhile, requirements for that very operation were moving to the front burner as letters outlining the military’s critical manpower needs were sent from Roosevelt, Marshall, and Chief of Naval Operations Ernest J. King to the House Military Affairs Committee, and released to the New York Times and other newspapers on January 17, 1945.  

The public was informed in front-page articles that: “The Army must provide 600,000 replacements for overseas theaters by June 30, and, together with the Navy, will require a total of 900,000 inductions.”

This was followed by Stimson's announcement that the Army’s monthly Selective Service call-up, which had already been increased from 60,000 to 80,000 in January 1945, was going to be ratcheted up yet again in March to 100,000 men per month in anticipation of the invasion of Japan.   Simultaneously, AGF replacement training centers were expanded, and reached a wartime peak of 400,000 in June, months after US divisions had pulled to a halt along the Elbe River.

In any event, what this near-doubling of draft quotas meant in terms of the planned invasions of Japan was essentially this: Starting in March 1945, when levies were increased to 100,000 per month for the US Army and 40,000 for the Navy and Marines, nearly every man inducted would enter the “replacement stream” now oriented for a one-front war against Japan.   The Army did not sugar coat the prospect of a long, bloody war for the soldiers in the field and new inductees, and warned that various “major factors--- none of them predictable at this stage of the game--- will decide whether it will take 1 year, 2 years or longer to win the Far East war.”

By May 1945, the US was already several months along this Selective Service track to compensate for roughly the same quantity of casualties over the one-year period starting with the initial invasion operation, Olympic in the fall of 1945, as it had during the one-year "casualty surge" that began in June 1944.   At this point, however, two things happened: (1) the discovery that the Japanese Army--- on Japan itself--- was gearing up to be nearly twice as large as the estimated 3,500,000 our original manpower requirements were based on, and (2) Okinawa--- that the Japanese were capable of inflicting casualties at a much higher rate than anticipated.

The clock was ticking.   And the crux of this problem facing Stimson and the rest of the senior leadership had to do with the casualty ratios emerging from Okinawa which, if duplicated in Japan's Home Islands, threatened to outstrip the carefully constructed replacement stream for troop losses projected through the end of 1946.   This was both a military and political problem.

Early in 1945 Stimson, in conjunction with Marshall, and then Director of the Office of War Mobilization Jimmy Byrnes (Truman's future Secretary of State), had worked out the huge increase in Selective Service call-ups and other manpower issues at the exact time that numbers were being crunched within the Army to ensure that the criteria for a partial demobilization of the longest-serving troops through the "Points System" would not be so drastic as to harm further operations against Japan.  By May the politically painful Selective Service increase had been under way for several months, and the Administration was now publicly committed to the partial--- yet still huge--- mid-war demobilization.   However, when the emerging ratio from Okinawa was extrapolated against the projected troop strength resulting from the increased call-ups and concurrent demobilization, it was apparent that the Army was in danger of finding itself in a "manpower box" in which its 100,000-man-per-month replacement stream, originally believed to be more than adequate for both Olympic in 1945 and Operation Coronet in 1946 on the Tokyo Plain, would fall far short of combat needs during Coronet which involved two, then eventually three, field armies.

Military Intelligence officers in the Pentagon were beginning the process of crunching the new Japanese force structure figures and coming up with decidedly unsettling results.   And at this point in May, Stimson was also still trying to arrange a meeting between the new president and Stimson's old boss when he was secretary of state, that incurable number cruncher, Herbert Hoover, who had been testifying before multiple Congressional committees on some of the troublesome aspects of America's mobilization.

Truman and Hoover would finally have their meeting on May 24, and Hoover followed up, at Truman's request, with a memorandum which, in the middle of the bloody fighting on Okinawa, predicted up to 1,000,000 American dead during the invasion of the Japanese Home Islands--- a mortality figure double what the Army staff had used as the maximum for the manpower policy it was already intricately involved in carrying out.  Two criticisms of Hoover's figures were supplied by Marshall's staff, with Stimson, who by now was highly skeptical of the Army's official estimates relating to manpower issues, forwarding neither to Truman.

As for Hoover and his memorandum, it is well known to students of the era, but until recently it was generally assumed by both president's critics that Hoover had likely pulled the number out of thin air.   What we now know, thanks to the recently retired senior archivist at the Hoover Presidential Library, Dwight Miller, is that the estimate almost certainly originated during Hoover’s regular--- and unofficial--- briefings by Pentagon intelligence officers, a group working under assistant chief of staff for intelligence, Major General Clayton Bissell, that Robert Ferrell wryly refers to as "a cabal of smart colonels."   Interestingly, someone high up within the Navy--- apparently still angling in support of the Navy's advocacy of a strategy of blockade and bombardment instead of invasion--- also took it upon themselves to leak both the revised Japanese troop strength and the markedly higher US casualty estimates that they generated.

Truman forwarded Hoover's memorandum to the director of the Office of War Mobilization and Reconversion, Fred M. Vinson, who had no quarrel with the casualty estimate and suggested that Hoover’s paper be shown to Acting Secretary of State Joseph Grew, former Secretary of State Cordell Hull, and Stimson (who was already completely familiar with Hoover's views).   On June 9, Truman sent copies of the memo to all three men, asking each for a written analysis of it and summoning Grew and Stimson to a meeting to discuss their analysis with him.  

None of Truman's senior advisor's batted an eye at the estimate.   Grew confirmed 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."   Stimson wrote: “We shall in my opinion have to go through a more bitter finish fight than in Germany.”

Truman's reaction was to call a meeting of the Joint Chiefs of Staff, Stimson, and Navy Secretary James Forrestal, for the following Monday afternoon, June 18, to discuss “the losses in dead and wounded that will result from an invasion of Japan proper.”

At the meeting all the participants agreed that an invasion of the Home Islands would he extremely costly, but that it was essential for the defeat of Imperial Japan.   As for Truman, he said that he “was clear on the situation now and was quite sure that the Joint Chiefs should proceed” but expressed the hope “that there was a possibility of preventing an Okinawa from one end of Japan to the other.”

Stimson, meanwhile, had been far from idle.   Returning to the never-ending manpower issue that had been severely complicated by the Japanese increases in the size of the Imperial Army, Stimson instituted an in-depth examination of the Army's replacement system as well as the underlying assumptions concerning the ultimate cost in killed and wounded that America could expect to suffer.   But having been burned--- in his opinion--- on multiple occasions by the Army's firm assurances that it had a better understanding of all the factors involved, Stimson specifically wanted, as noted earlier, civilian personnel not connected to AGF or the Army Staff to be called in to scrutinize manpower needs.

On the same day that Truman sent Hoover's memorandum to Grew, Hull, and Stimson, Stimson began his own initiative by directing Drs. E. P. Learned and Dan Smith, Harvard Business School economists on General Hap Arnold's Army Air Force staff, to take an independent look at AGF manpower and training requirements for the duration of the war against Japan.   Marshall who shared an adjoining office with Stimson, wisely kept completely out of the way of what quickly became known as the Learned-Smith Committee.

Another facet of Stimson's effort was handled by his special assistant, Dr. Edward Bowles who initiated a study on possible casualties that the Japanese as a nation might be able to inflict on an invasion force.   It included Dr. Quincy Wright from the University of Chicago and was headed up by future Nobel laureate Dr. William B. Shockley who was "on loan" to the effort from the Navy, where he served as director of research for the Antisubmarine Warfare Operations Research Group.  They were given full access to key intelligence and planning personnel, including Colonels James McCormack and Dean Rusk, intelligence officers and former Rhodes Scholars on the Operations Division's small but influential Strategic Policy Section, as well as highly classified Pentagon manpower and casualties data including the top-secret analyses of escalating US troop losses produced by Drs. Michael DeBakey and Gilbert W. Beebe.

This was quite a line-up.   Dr. DeBakey, then an Army Medical Corps colonel, would become the principal proponent behind development of MASH units and be well known to the public for his work in the field of heart surgery.   Shockley?   He was still a decade away from being awarded a Nobel Prize for his part in the development of the transistor.   Wright, who had written the two-volume A Study of War; was not a spring chicken, having received his degree at the University of Illinois in 1915, but very shortly after taking part in Stimson's initiative he entered the Army; was given the rank of colonel; and served as a technical advisor to the Nuremberg Tribunal.   Learned and Smith were already well known in the economics field and Learned's case study method is still used today as an instructional process.   McCormack was soon appointed director of the of the Atomic Energy Commission's Military Application Division, and transferred to the Air Force where he rose to major general, while Beebe played a key role in both the formation and continuing operations of the Atomic Bomb Casualty Commission.   As for Rusk, he would have a long and distinguished career in government service.

But getting back to Stimson's initiative, beyond the officially stated reason for its formation, the low-visibility Learned-Smith Committee was created as a backstop to answer anticipated public--meaning Congressional--inquiries into the need for continued high Selective Service call-up rates and the possibility that deferments, already generating loud protests from their tightening during the run-up to the invasion of Japan, might be squeezed even further.   Other efforts, like that of the Shockley-Wright study, were geared to helping frame further discussion.

The Shockly-Wright effort "to determine to what extent the behavior of a nation in war can be predicted from the behavior of her troops in individual battles" concluded that: "If the study shows that the behavior of nations in all historical cases comparable to Japan's has in fact been invariably consistent with the behavior of the troops in battle, then it means that the Japanese dead and ineffectives at the time of the defeat will exceed the corresponding number for the Germans.   In other words, 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 and 800,000 killed."

As for the Learned-Smith Committee, when its report was made available in late June, AGF generally concurred with the committee's findings and was greatly relieved to find that the committee agreed with the current Army policy of producing replacements "against maximum requirements rather than against continually revised estimates of minimum needs."   In fact, this conclusion also has relevance for today since it can be argued that some revisionist historians (safely removed six decades from events) as well as a significant number of politicians are "minimum needs" advocates.

So what came of all this?   Essentially nothing.   The sudden and unexpected end of the war eliminated the need for these taskings before Stimson may have seen what Bowles turned up, but it is important to remember that Stimson himself initiated these efforts.   A very lengthy memorandum prepared by Colonel (later Brigadier General) John Banville for the committee apparently became much of the basis of an AGF study on replacements, and was further absorbed into the official Army history of the AGF.   And as for the Shockly-Wright study, it languished deep in the Bowles Papers at the Library of Congress, and likely elsewhere, for five decades until it was retrieved by Professor Robert P. Newman.

The irony of this is that for many years, various individuals critical of Truman's bomb decision regularly maintained that estimates of massive casualties during an invasion of Japan were a post-war creation, and when the copious documentation that they were wrong began to come to light a decade ago, then switched to the line that the estimates must certainly have been developed and seen only by "lowly subordinates" when, in fact, far from being considered by obscure officers tucked away in the recesses of the Pentagon, this vital--and highly secret--matter was being examined by some of the finest minds this country has produced from Henry Stimson to Michael DeBakey.   Moreover, Truman had not simply seen the genuinely huge numbers, but reacted decisively to them by calling the June 18, 1945, White House meeting in which the invasion of Japan was given the go-ahead in spite of their frightful dimensions.