FDR and the bomb

by Alex Wellerstein, published September 30th, 2016

Franklin D. Roosevelt is one of the most enigmatic figures of the early American atomic bomb program. The four-term US president always features briefly in any story of the Manhattan Project: first, for his creation of the Advisory Committee on Uranium, an exploratory research effort in response to a letter urging government action that was sent by Albert Einstein in August 1939; second, for his approval of a broader expansion of that research into a “pilot” program in late 1941, just before the US entry into World War II, which resulted in more intensive investment into uranium enrichment and reactor design; and third, in mid-1942, Roosevelt approved bringing in the US Army Corps of Engineers to manage a full-scale bomb-production project. This latter action is often subsumed by the attention given the first two, but it is the production program decision that actually resulted in the US getting an atomic bomb by 1945, and is the decision that makes the United States unique among powers in the Second World War, as while several powers had research programs, only the US turned it into a production program. It was the beginning of the Manhattan Project as we tend to characterize it, the kind of program that produces weapons and not just data.

A little history trick I always tell my students: if you see Truman and FDR in the same photograph, that means Truman doesn't know about the atomic bomb. Photo source:

A little history trick I always tell my students: if you see Truman and FDR in the same photograph, that means Truman doesn’t know about the atomic bomb. Photo source:

So Roosevelt looms large, as he ought to. Without Roosevelt’s actions, there would have been no atomic bomb in World War II. And yet… What did FDR really think about the atomic bomb? Did he see it as a true end-the-war weapon? Did he think it was meant to be used in war (as a first-strike weapon) or did he think of it primarily as a deterrent (i.e., against the Germans)? The question isn’t just an idle one, because Roosevelt’s sudden death, on April 12, 1945, left his successor, Harry Truman, with major decisions to make about the future of the war, and Truman, in part, thought he was acting in accordance with FDR’s wishes on this matter. But, as is well known, FDR never told Truman about the atomic bomb work, and never set out his wishes on this matter — so there was a tremendous amount of assumption involved.

I get asked about FDR’s views on a fairly regular basis, and it’s one of those wonderful questions that seems simple but is really quite complex, and quickly gets you into what I think of as “epistemological territory”: How do we know what someone’s views were, in the past? How do we get inside the head of someone dead? Well, you might say, obviously we can’t completely get inside someone’s head (we can barely get inside the heads of people who are alive and in front of us, and a Freudian might argue that we barely have conscious access to our own motivations and thoughts), but we can look at what evidence there is that was written down that might reveal some of their inner thoughts.

But with FDR, this is very tricky: he didn’t write that much down. He didn’t keep a diary or journal. He didn’t send that many letters. He didn’t record phone calls, conversations, write “memos to self,” or any of the other documenting habits that are common to major political figures. He was notoriously secretive and private. He didn’t explain himself. If Truman was comparatively straightforward in his thinking and action, Roosevelt was a grand schemer, trying to out-wit and out-charm the world (sometimes successfully, sometimes not). He could be downright gnomic. At one point, Vannevar Bush (FDR’s top science advisor) asked Roosevelt whether the Secretary of the Navy ought to be included in discussions on the bomb project. He later recalled that FDR “looked at me with one of his strange smiles and said, ‘No, I guess not, not now.'” End of anecdote, no real indication as to what FDR was thinking, other than a “strange smile” that no doubt concealed much.1

What approval of a nuclear weapons program looked like under Roosevelt: "VB OK FDR." Report by Vannevar Bush of June 16, 1942, asking to expand the fission work into an all-out effort.

What approval of a nuclear weapons program looked like under Roosevelt: “VB OK FDR.” Report by Vannevar Bush of June 16, 1942, asking to expand the fission work into an all-out effort.

As this example indicates, we do sometimes have accounts, including contemporary ones, by people who met with Roosevelt and talked with him. But even these can be quite tricky, because FDR did not, again, generally explain his full thinking. So people like Bush were left with half-versions of the story, knowing what FDR said but not what he thought, and while this is, to be sure, a common-enough human experience, with FDR the gap between thought and expression was exceptionally large.

Separately, there is another, related issue that complicates our understanding: people who met with FDR would often use tales of his agreement as a form of authority. Vannevar Bush did this repeatedly, and this is no doubt a pretty standard mode of operation regarding advisors and presidents. Bush would go to FDR with an idea, convince FDR to sign off on Bush’s idea, and then claim it was FDR’s idea, because while people might feel free to disagree with Bush, they couldn’t really disagree with FDR. One of the most famous examples of this is Bush’s report on postwar American science policy, Science—The Endless Frontier, which is constructed to look like it is a reply to a letter by FDR for guidance, but was entirely engineered by Bush as a means of pushing his own agenda, with FDR being a complicit as opposed to a driving force.2

So what do we know? The number of documents that give insight into FDR’s personal thoughts about the atomic bomb — what it was, what it could be used for, what his plans were — are very slim. Some of this is a function of timing: FDR died right around when they were getting concrete estimates for when the atomic bomb would be ready to use, and had he lived until, say, May 1945, he might have been faced with more direct questions about his plans for it. (The first Target Committee meeting was on April 27, and the Interim Committee was created in early May, just to give an indication of how things rapidly started to come together right after FDR died.) So he wasn’t part of the conversations that directly led to the use of the atomic bombs on Japanese cities.

But there are a few other documents that are useful in assessing FDR’s views. It seems fairly clear that FDR’s approval of the Uranium Committee in 1939 was initially because he was interested in the deterrent quality of the bomb. Alexander Sachs, who had the meeting with Roosevelt, related that FDR had confirmed that the goal was “to see that the Nazis don’t blow us up.”3 Again, this wasn’t yet a bomb-making program, it was just a “see if bombs are worth worrying about” program, but that’s still a little insight: it shows, perhaps, that the initial, explicit attraction was not in making a new wonder-weapon, but deterring against another one.

Roosevelt, Truman, and FDR's previous VP, Henry Wallace. Truman is the only one here who doesn't know about the bomb program. Image source: Truman Library via Wikimedia Commons

Roosevelt, Truman, and FDR’s previous VP, Henry Wallace. Truman is the only one here who doesn’t know about the bomb program. Image source: Truman Library via Wikimedia Commons

Between 1939 and 1941 there are big gaps in anything that would indicate FDR’s views on the bomb. This is not surprising, because this was a period of relative lack of movement in the US fission program, which was not yet a bomb program. FDR was occasionally involved in discussions about the program, but there was no “bomb” yet to worry about one way or the other. In late 1941, FDR approved accelerating and expanding the research, at the urging of Bush, James Conant, Ernest Lawrence, and Arthur Compton, and in mid-1942 he approved of a full bomb production program, as previously noted. None of these documents indicate intent for use, however. The June 1942 report by Vannevar Bush and James Conant, whose approval by Roosevelt is indicated only by a scrawled “VB OK FDR” on its cover letter, indicates that a weapon made with 5-10 kilograms of U-235 or Pu-239 (then just called “Element 94”) would have an explosive power of “several thousand tons of TNT.” It goes into great detail on the types of plants to be constructed and the organization of the research. It predicts a “bomb” would be ready by early 1944. But at no point does it indicate what the point of such a weapon was: as a deterrent, as a first-strike weapon, as a demonstration device, etc. There is only point, towards the end, which suggests that a committee be eventually formed to consider “the military uses of the material,” but even this is primarily concerned with research and development for the plants. This is not to say that Bush, Conant, et al. did not have their views on whether it would be a weapon to use or not — but the report does not indicate any such views, and so FDR’s endorsement of it doesn’t tell us much.4

Bush met with Roosevelt many times during the war, and sometimes would write down, afterwards, what they talked about. Clearly this is FDR-as-filtered-through-Bush, but we’ll take what we can get. In late June 1943, Bush wrote to Conant with an account of a recent meeting he had with FDR on “S-1,” their code for the bomb work. In it, Bush related that FDR was curious about the progress of the work and the schedule for having a bomb. Bush told him things were going well but still tentative, and that the date of a bomb had been pushed back to early January 1945, but that this could shift in either direction. FDR also wanted to know how the Germans were doing. Bush explained that they didn’t really know, that they were trying to find ways to slow down any German work, and that they were still worried about being behind the Germans. (They would eventually come to understand they had surpassed them.) Then there is this really interesting passage which is worth quoting from the original:

He [FDR] then himself discussed what the enemy attitude of mind would be if they felt they had this coming along, and were inclined to remain on the defensive until it could eventuate. We then spoke briefly of the possible use against Japan, or the Japanese fleet, and I brought out, or I tried to, that because at this point I do not think I was really successful in getting the idea across, that our point of view or our emphasis on the program would shift if we had in mind use against Japan as compared with use against Germany.5

After which the conversation then shifted to other matters. Such a tantalizing snippet of discussion, but not as fleshed out as one might want! What did Bush and FDR understand the difference to be between the Japanese versus the Germans? Who initially brought up the possibility of use against the Japanese? What did FDR think about the German “attitude of mind”? This snippet hints at exactly the topics one might care about but doesn’t actually reveal anything about FDR’s views on them! Impressively frustrating!

Most of FDR’s interactions with Bush, Groves, and others during this period concerned diplomatic issues, specifically cooperation with the British (a rather long, drawn-out saga), and even a meeting with Niels Bohr (from which FDR mostly took away a fear that Bohr might alert the Soviets, or others, to the US work). FDR helped, for example, in helping to shut down unionization activities at the Berkeley Radiation Laboratory, and was kept abreast of efforts made to monopolize global uranium ore resources. He was not “checked out” in any respect; he was dramatically more concerned with the ins-and-outs of the fission work than, say, Truman would later be. But again, very little of this left any record about what he thought they were going to do with the bomb.6

Atomic diplomacy: Roosevelt and Churchill at Quebec, in September 1944. Source: NARA via Wikimedia Commons

Atomic diplomacy: Roosevelt and Churchill at Quebec, in September 1944. Source: NARA via Wikimedia Commons

Two of the only documents that reveal any FDR-specific thoughts about the use of the bomb were agreements he made with Winston Churchill. In August 1943, Churchill and Roosevelt met in Quebec, Canada, and hammered out the secret “Quebec Agreement.” It said, among other matters, that the US and UK would pool their efforts at both making the bomb and securing global uranium reserves, that they would never nuke each other, that they would never nuke anyone else without mutual agreement, and they would not reveal the secrets of the bombs without mutual agreement. So this at least provides a framework for using the bomb, but it is a limited one — FDR was willing to deliberately tie the US’s hands with regards to dropping of the atomic bomb to the approval of a foreign power, quite an amazing concession!7

Another meeting between Roosevelt and Churchill, in Hyde Park, New York, produced yet another fascinating agreement. The Hyde Park Aide-Mémoire of September 1944 contained the following clause:

The suggestion that the world should be informed regarding tube alloys, with a view to an international agreement regarding its control and use, is not accepted. The matter should continue to be regarded as of the utmost secrecy; but when a “bomb” is finally available, it might perhaps, after mature consideration, be used against the Japanese, who should be warned that this bombardment will be repeated until they surrender.

Here they were explicitly rejecting the appeal by Niels Bohr (which he was able to make personally to both FDR and Churchill, on separate occasions) to alert the world about the atomic bomb. But it is of interest that they were, at this point, specifically thinking about using the bomb against the Japanese (not Germany), but that they thought it would require “mature consideration” before use, and that they were putting “bomb” in scare-quotes. This is one of the few indications we have of FDR’s awareness and acceptance of the idea that the bomb might be used as a first-strike weapon, and against the Japanese in particular.

Lastly, there is one other significant FDR-specific datapoint, which I have written about at length before. In late December 1944, with Yalta looming, Roosevelt and Groves met in the Oval Office (along with Henry Stimson, the Secretary of War). In Groves’ much later recollection (so we can make of that what we will), Roosevelt asked if the atomic bomb might be ready to use against Germany very soon. Groves explained that for a variety of reasons, the most important one being that their schedule had pushed the bomb back to the summer of 1945, this would not be possible. It is an interesting piece, one that simultaneously reveals Roosevelt’s potential willingness to use the atomic bomb as a first-strike weapon, his willingness to use it against Germany specifically, and the fact that FDR was sufficiently out of the loop on planning discussions to not know that this would both be impossible and very difficult. In other words, it reveals that FDR wasn’t aware that by that point, it was expected that the bomb could only be used against Japan, and that is a rather large thing for him not to know — further evidence, perhaps, that he was not completely abreast of these kinds of discussions. At the meeting, Groves gave FDR a report that predicted a weapon ready for use in early August 1945, and specified that it was time to begin military planning, which Groves annotated as having been “approved” by the Secretary of War and the President. But there doesn’t seem to have been any specifics of targets, or even targeting philosophy, agreed upon at this point.8

What can we make of all this? Frequently I have seen people take the position that Truman himself took: assuming that Roosevelt would have used the bomb in the way that Truman did, because what else might he have been planning? I would only caution that there were more “options” on the table even for Truman than we tend to talk about, which is just another way to say that dropping two atomic bombs in rapid succession on cities is not the only way to use an atomic bomb even militarily. That is, even if one thinks it was inevitable that the bombs would be used in a military fashion (which I think is probably true), it is unclear what position FDR might have taken on the question of specific targets (e.g., the Kyoto question), the question of timing (e.g., before or after the Soviet invasion; how many days between each strike?), and diplomatic matters (e.g., would Roosevelt be more open to modifying the Potsdam Declaration terms than Truman was?). So there is room for considerable variability in the “what if Roosevelt hadn’t died when he did?” question, especially given that Roosevelt, unlike Truman, had been following the bomb work from the start, and was as a result much less reliant on his advisors’ views than Truman was (he frequently bucked Bush, for example, when it came to matters relating to the British).

Would Roosevelt have dropped the bomb on Japan, had he not died? I suspect the answer is yes. One can see, in these brief data points, a mind warming up to the idea of the atomic bomb as not just a deterrent, but a weapon, one that might be deployed as a first-strike attack. In some ways, FDR’s query to Groves about Germany is the most interesting piece: this was a step further than anyone else at the time was really making, since Germany’s defeat seemed inevitable at that point. But, again, the strict answer is, of course, that we can’t really know for sure. Perhaps if FDR had confided his inner thoughts on the bomb to more people, perhaps if he had written them down, perhaps if he had been more involved in the early targeting questions, then we would be able to say something with more confidence. Unless some new source emerges, I suspect Roosevelt’s thoughts on the bomb will always have something of an enigma to them. It is not too far-fetched to suggest that this may have always been his intention.

  1. Vannevar Bush, Pieces of the action (New York: Morrow, 1970), 134. []
  2. See Daniel J. Kevles, “The National Science Foundation and the Debate over Postwar Research Policy, 1942-1945: A Political Interpretation of Science–The Endless Frontier,” Isis 68, no. 1 (1977), 4-26. Another example of this behavior, from my own research, is when Bush wanted to seize patent rights relating to atomic research during the war — this was an idea cooked up by Bush, approved by FDR, and then presented as an idea of FDR’s, to give it more political, legal, and moral heft. See Alex Wellerstein, “Patenting the Bomb: Nuclear Weapons, Intellectual Property, and Technological Control,” Isis 99, no. 1 (2008), 57-87, esp. 65-66. []
  3. Quoted in Richard Rhodes, The Making of the Atomic Bomb (Simon and Schuster, 1986), on 314. []
  4. Vannevar Bush and James Conant, “Atomic Fission Bombs,” (17 June 1942), with attached cover letter initialed by Roosevelt, copy in Harrison-Bundy Files Relating to the Development of the Atomic Bomb, 1942-1946, microfilm publication M1108 (Washington, D.C.: National Archives and Records Administration, 1980), Folder 58: “Vannevar Bush Report – March 1942,” Roll 4, Target 4. []
  5. Vannevar Bush to James Conant, “Memorandum of Conference with the President,” (24 June 1943), copy in Bush-Conant File Relating the Development of the Atomic Bomb, 1940-1945, Records of the Office of Scientific Research and Development, RG 227, microfilm publication M1392, National Archives and Records Administration, Washington, D.C., n.d. (ca. 1990), Roll 2, Target 5, Folder 10, “S-1 British Relations Prior to the Interim Committee [Fldr.] No. 2 [1943, some 1944, 1945].” []
  6. For a very nice discussion of Roosevelt’s wartime “atomic diplomacy,” see Campbell Craig and Sergey Radchenko, The atomic bomb and the origins of the Cold War (Yale University Press, 2008), chapter 1, “Franklin Delano Roosevelt and Atomic Wartime Diplomacy,” 1-33. On the UK-US atomic alliances, see Barton Bernstein, “The uneasy alliance: Roosevelt, Churchill, and the atomic bomb, 1940-1945,” Western Political Quarterly 29, no. 2 (1976), 202-230 []
  7. And just to follow up on that: the US did, in the summer of 1945, request formal UK approval for the dropping of the atomic bomb, and for the release of the Smyth Report and other publicity. The UK readily gave assent to using the weapon against the Japanese, but they did question the wisdom of releasing the Smyth Report. They eventually consented to that as well, after stating their reservations. []
  8. Just as an aside: the meeting, by Stimson’s diary account, was only 15 minutes long, and most of it pertained to questions of diplomacy (specifically potential British violations of the Quebec Agreement with respect to French patent arrangements). Stimson’s diary entry mentions nothing about targeting question, German, Japanese, or otherwise. So either the discussion of Germany and Japan did not make much impression on him, or he did not think it prudent to write it down. See Henry Stimson diary entry for December 30, 1944, Yale University. Groves own contemporary record of the meeting also neglects to mention anything relating to targets, and instead is entirely focused on diplomatic questions. Leslie Groves, Memorandum on Meeting with President (30 December 1944), Correspondence (“Top Secret”) of the Manhattan Engineer District, 1942-1946, microfilm publication M1109 (Washington, D.C.: National Archives and Records Administration, 1980), Roll 3, Target 7, Folder 24, “Memorandums to (Gen.) L. R. Groves Covering Two Meetings with the President (Dec. 30, 1944, and Apr. 25, 1945).” []

25 Responses to “FDR and the bomb”

  1. Peter says:

    Roosevelt’s failure to inform Truman of the bomb program is especially puzzling given that Roosevelt’s health was failing before he started his fourth term and he surely would have known there was a substantial chance Truman would have jto become president. Roosevelt was losing weight at an alarming pace (188# to 165# in the three months leading up to the 1944 election), was suffering from angina attacks, and quite possibly had cancer. Yet for some reason he was willing to let Truman remain ignorant.
    Trivia: Roosevelt’s arteries were so atherosclerotic that embalming his body was extremely difficult.

  2. Bradley Laing says:

    September 1944 contained the following clause:

    The suggestion that the world should be informed regarding tube alloys, with a view to an international agreement regarding its control and use, is not accepted. The matter should continue to be regarded as of the utmost secrecy; but when a “bomb” is finally available, it might perhaps, after mature consideration, be used against the Japanese, who should be warned that this bombardment will be repeated until they surrender.

    —-Do we know for a fact that “be used against the Japanese” meant the word “Cities” in September of 1944? Or were there still big enough military targets that if hit, in September of 1944, would change the Japanese governments minds?

  3. Bradley Laing says:

    —-I know from the article that the first deliverable bomb was thought to be ready in January of 1945. Was there a conviction in September of 1944 that there would be no important Japanese military things to nuke by January of 1945?

    • Do you mean Germany or Japan? For Japan — plenty of targets still. (Firebombing didn’t start until March 1945, and that wasn’t planned out long in advance.) For Germany — they felt that the Germans would fold up pretty quickly in 1945, but that was optimistic.

  4. Michel Leduc says:

    Thank you for this excellent text. I am surprised that FDR was so withdrawn in his commentaries on the Manhattan Project.
    One thing that I do find strange is the way FDR treated Truman during his 82 day vice-presidency. The fact that Truman was not informed about the Project and his predecessor, Wallace, knew about it, suggests that FDR had really no confidence in his new vice-president. How strange…

    • FDR was the one who imposed the tremendous secrecy on the project, so it’s not too surprising he didn’t commit much to writing or tell too many other people (though the question of why he was so specifically obsessed with secrecy about this project, above all others, is an interesting one in and of itself). Keeping Truman out of the loop, though, does seem to have been very deliberate (his previous VP, Henry Wallace, was deeply involved in Manhattan Project planning), and arguably quite irresponsible!

  5. Stan Norris says:


    The December 30 meeting with FDR took place in the midst of the Battle of the Bulge which was a concern of the President’s. In a Memo to the File 20 years later Groves had this to say “In Dec. 1944, FDR, discouraged by reason of the Battle of the Bulge, did tell me he thought the war might be prolonged and that we should be prepared to use the bomb against Germany.” The citation is in my book, footnote 25 on page 647.

    • Right. What I’ve found interesting though is that there is no contemporary record of any of that aspect of the conversation — neither Groves nor Stimson saw fit to put it into their respective memos about the meeting, or Stimson’s diary. Which doesn’t mean it didn’t happen — it sounds plausible enough — but its an interesting thing in and of itself.

      • Stan Norris says:


        Looking into it a bit more I can add the following

        The AAF in WWII, Vol. V, p. 709.

        “Since 1941 he [Stimson] had been “directly responsible to the President for the entire [atomic bomb] undertaking”; under Stimson was Groves who (after I 942) was in charge of the developmental program and apparently had some illdefined concern with the employment of the bomb, According to Stimson, there was never any question in Roosevelt’s mind but that the bomb would be used when ready and this attitude was adopted by Mr. Truman when he acceded to the presidency in April 1945 and first learned the details of the project.” By that time the military preparations for the possible use of the bomb against Japan were already well advanced, as the previous pages have shown; the estimate by informed scientists that the first model would be ready by midsummer.”

        Manhattan District History, Book 1, Volume 1, Section 2.1

        “Reduced to its simplest terms, the mission of the Manhattan District was to develop and manufacture atomic bombs for combat use, at the earliest possible date, and ahead of the enemy, in order to help the United States and its Allies bring World War II to a successful conclusion with the least delay and the greatest possible conservation of life.”

        As Secretary of War Stimson later said: “At no time, from 1941 to 1945, did I ever hear it suggested by the President, or by any other responsible member of the government, that atomic energy should not be used in the war.” Henry L. Stimson and McGeorge Bundy, On Active Service in Peace and War (New York: Harper & Brothers, 1947), 613.

        My last paragraph, from “On President Truman’s Use of the Atomic Bomb” in Walker, J. Samuel, Nuclear Energy and the Legacy of Harry S. Truman (Kirksville, Missouri: Truman State University Press, 2016), p. 72.

        Even if Roosevelt had lived until July and August 1945 little would have been different in the use of the bomb. The plutonium and HEU were ready no matter who was president and that had always been the key factor in the timing of its use. The press releases and other information were being crafted to explain what had transpired and the United States would have entered the Atomic Age in early August 1945.

        • Hi Stan,

          I’m distrustful, I will say, of Stimson’s postwar claims to FDR’s assent. Even if one assumes Stimson was entirely truthful in his belief that he knew FDR’s thoughts, it is not a direct line to FDR. And there are very good reasons to be suspicious that Stimson in this instance (as he did with others) somewhat “re-wrote” or “massaged” his memory in order to make everything seem more orderly than it might otherwise had been.

          On the use of the bomb, as I wrote, I think it extremely probable that FDR would have wanted to use the bomb in some way. But there are many sub-questions about what exactly “use” might mean. Would FDR have found Stimson equally compelling on the topic of Kyoto? Would he have had his own scheme for how to otherwise induce surrender? Would he have modified the Potsdam Declaration, and would that have changed things? Would he have modified the schedule vis-a-vis the Soviet invasion? Etc. These all seem to me to be unanswerable.

          I think FDR would use every resource at his disposal — but that doesn’t necessarily mean it would be lock-step with what Truman did, some of which was indeed quite specific to Truman’s own judgment, advisors, etc.

    • C S V says:

      Conversely, the September 18 meeting between Roosevelt and Churchill took place before the setbacks of Market-Garden (then in its 2nd day) and the Bulge, when it seemed as if Germany might be knocked out of the war faster than it actually was. Discussing use against Japan alone simply reflected their optimism.

  6. M Tucker says:

    Great post Alex! I was wondering if you have any comment on this:

    Nigel Hamilton, historian and biographer (several on Montgomery among many others), is writing a three volume (I’m pretty sure it will end up as three volumes) biography on FDR’s war years. In his second volume, covering the first two thirds of 1943, Hamilton asserts that in order to stop Churchill’s waffling on a commitment to a cross-channel invasion in the spring of 1944, FDR presented him with an ultimatum: either commit to the invasion in the spring of 1944 or the US would not share the fruits of the atomic bomb project. According to Hamilton, FDR delivered his ultimatum to Churchill at Hyde Park prior to the Quebec conference. He presents this, to my mind extraordinary, episode of “history” without notation. That makes me suspicious that it really happened and sends up the alarm that Hamilton could not find any specific mention of the ultimatum in Stimson’s, or anyone else’s, diary or meeting notes.

    Have you ever heard of such an ultimatum?

    • I have seen it implied that this was the reason behind FDR’s interest in partnering with Churchill on the bomb work (against the efforts of many of his advisors, who thought it was too one-sided in favor of the British), but I haven’t seen anything very concrete about it.

  7. Ross Mallett says:

    In his memoirs Truman claimed that he did not know about the Manhattan Project until after he became president, but as head of the Truman Committee (a Senate Committee investigating war effort-related waste) both Groves and Stimson record he was informed of the project by Stimson. We don’t know how much he was told about it.

    The problem with Truman is that his memory has been demonstrated to be faulty on so many, many occasions, especially regarding the atomic bomb, but there was an ethos until the 1960s that the president was always right and could not be challenged.

    In your opinion, was the crusading senator likely to have been so easily fobbed off by being told it was a big secret? Did he have anything to gain by professing that he had not been informed?

    • There is an indication that he got some kind of information from a side-channel. After being warned off of the project the first time, in 1943, he wrote to a judge in Spokane, Washington, that “I have been informed that it is for the construction of a plant to make a terrific explosion for a secret weapon that will be a wonder.” Which, of course, is ironically exactly the reason that they didn’t want to bring him in on the project — Congressmen are notorious leakers. Did Truman thus know what was going on? It depends on what “know” means here — he knew something but he probably was only told something about as vague as what he wrote to the judge, not specifics.

      Truman tried to get info about the project late 1943 and March 1944 as well. He was one of many Congressmen they had to deal with.

  8. Roger Murray says:

    Are there any clues to be found in Churchill’s writings? I would think that he would have been in the middle of it all, trying to run things, if he was even remotely aware of the program.

    • That’s an interesting question — I haven’t looked. He was kept abreast about many things going on in the Manhattan Project, but I am not sure I have seen anything where he gave an indication of FDR’s position.

  9. Ryan Crierie says:

    Here’s a scan of that December 30, 1944 memo with the handwriting.
    5 MB PDF.

    It’s from a 2008 or 2010 visit to NARA II where I trawled RG77: MED.

    • Thanks — that’s a good one to have!

    • Allen Thomson says:

      Sorry to be a bit late, things intervened.

      But look at the estimates for the yield of the Pu implosion bomb! Way, way under what was achieved at Trinity and Nagasaki and the estimates were less than a year away from the explosions. Are there any other documents that agree with this low-ball estimate?

      • The most optimistic estimate going into Trinity was 5 kilotons. So even at that late date, they were far more pessimistic about the efficiency of the implosion.

        The implosion estimates were pretty low (700-5,000 tons) at the May 1945 Target Committee meeting as well.

        In general it is clear that they did not have a lot of confidence in first-gen implosion efficiency until after Trinity. It’s not super surprising — the whole point of Trinity was because of their lack of confidence and their lack of an easy ability to test the method without a full-scale approach. (As opposed to Little Boy, which was much simpler in every way.)

        • Allen Thomson says:

          Quite interesting. I wonder if the uncertainty came from the implosion process itself and/or plutonium compressibility, both of which are non-nuclear, or something to do with the actual nuclear physics. Or all of the above.

          • What they understood the least were the hydrodynamic aspects of trying to do spherical implosion. They had lots of good data on plutonium compressibility (P.W. Bridgman at Harvard, at the time the world expert on high pressures, did a lot of research for them on this using small samples of plutonium). What’s hard to know without full-scale testing is how simultaneity, jets, etc. would come into play during the actual reality (beyond theory) of the implosion process, so I understand it.