One of the weirdest stories I’ve come across regarding the Nazis and the atomic bomb is the one that the German physicist Werner Heisenberg told at Farm Hall about being asked about an apparent rumor that the United States was planning to use an atomic bomb against Dresden.

The Farm Hall transcripts reports him telling it several times during his internment, and it changed slightly each time he told it. Here’s the first version:

About a year ago, I heard from Segner from the Foreign Office that the Americans had threatened to drop a uranium bomb on Dresden if we didn’t surrender soon. At the time I was asked whether I thought it possible, and, with complete conviction, I replied: “No.”

In a later version, he says he replied that it was possible — perhaps a face-saving maneuver, since by the second time Heisenberg tells the story, he has now started to believe that the reports of the atomic attack against Hiroshima were accurate.

My initial inclination is to think of this as strange idle chatter amongst a group of interned German scientists. A little bit of rumor-swapping, bragging about being in-the-know and being someone worth consulting. But I don’t think Heisenberg just made it up. That’s not really his style, I don’t think, and he repeated it several times over the course of their six month stay at Farm Hall.

Recently, while looking into some other wartime leaks, I came across an interesting follow-up on this story. The leak in question is a weird one and worth sharing. In August 1944, a German science magazine, the Physikalische Blätter (Physical Newspaper/Gazette/Pages), ran a short, anonymous piece titled “Another Utopia“:

Transocean Service transmits a report cabled to “Stockholm’s Tidnigen” from London: “In the United States scientific research for a new bomb is underway. The material is uranium, and if the forces bound in this element could be liberated, explosive forces of so far unimagined power could be created. A 5-kilogram bomb could made a hole one kilometer deep and with a radius of 40 kilometers. In a circle of 150 kilometers all buildings were be smashed.”

That’s a pretty weird thing to just appear in a German magazine, no? To save you the effort: their math on the energy release is way off by any measure — the damage radius described is well over 100 megatons, which is around what you’d get if you combined 5 kg of uranium with 5 kg of anti-matter (a pure E=mc2 conversion), much less if it fissioned with perfect efficiency (which would “only” release 85 kilotons). Either they’ve carried a few decimal points incorrectly or they’re just really confused. I suspect the latter.

Was this a “legitimate” leak? That is, did it derive from disclosure of confidential information? It’s hard to tell. The fact that it pinpoints the United States as making an atomic bomb out of uranium seems accurate, but everything else seems to be sketchy and confused. It’s true that the plutonium bomb used only around 6 kg of material… but that almost seems like a coincidence given the rest of what they’re talking about here. I’m inclined to file this under “fantastic atomic energy rumors” which were common even before the discovery of fission.

Anyway. The interesting bit comes 20 years later, in 1964. Physikalische Blätter was (and is) still around, and they ran a story on their wartime leak story. Much of it is repetitive fluff, a by-the-book (for 1964) accounting of Allied and German nuclear research. But along with this, they did attempt to track down the origin of the leak — with no success. But they did decide, thoughtfully, to try and assess the impact of the leak by surveying a few of the Farm Hall physicists to see whether they were aware of the “Another Utopia” story.

Otto Hahn wrote back that he “knew nothing” of the article at the time, and added that while they knew that there were people abroad probably working on the subject of atomic bombs, and that the stopping of all publications about the subject probably indicated the work was secret, that nonetheless they didn’t suspect that the United States would actually be able to produce such weapons in time for use in the war. He then suggested that the Physikalische Blätter should get in touch with Heisenberg, since he was more plugged into such matters than Hahn.

And they did get in touch with Heisenberg, whose first response was that he hadn’t seen the article, was surprised to hear about it, suspected it was based on “vague rumors,” but said he would love if they sent him a copy so he could evaluate it further. They did this, of course, and his second response was the more interesting one. He said that rumors of this sort occurred repeatedly because of articles related to atomic energy that had already been published, and he did not let such rumors occupy him much during the war. But then Heisenberg wrote (my awkward translation — original German is in the footnotes):

Perhaps I should mention here an exception. In the summer of 1944 (probably early July), an aide of Göring’s came to me with a message from a German representative in Lisbon that there was a pronounced American threat against the German government, that an atomic bomb would be dropped on Dresden in the next six weeks if the government did not immediately sue for peace. The exact conditions of where the message came from were not communicated to me. I was asked by Göring’s adjutant if I thought it was possible that the Americans had already created an atomic bomb. I was understandably made very uncomfortable by this question, because of the large responsibility connected to my answer. I said that I thought it was extremely unlikely, but not impossible, for the Americans to have such a weapon at this time, and I tried to explain that the production of the weapon would in any case require an enormous industrial effort, and that I could not imagine that the Americans had already done it.

And so the Dresden atomic bomb rumor raises its head again, no less confounding than before! But here we have a little more information on the source: it is supposedly from an agent in Lisbon, Portugal. Which is interesting.

Because as Stan Norris communicated to me when I wrote about German espionage efforts, there was a Nazi double-agent in Lisbon who was assigned to learning about the Manhattan Project. Stan has since sent me a “note to file” that General Groves had written about a meeting he had with the Military Policy Committee on June 21, 1944, where he describes this incident and his response to it. In his notes, Groves wrote the following:

This refers to the German agents who came to this country through Portugal, and the messages that were sent back to Germany in their behalf. These people were picked up as soon as they got into the United States and the messages were framed by me. There was considerable argument by my creeps as to these messages. I overruled them and did not deny that certain work was being done. It was pinpointed at certain universities and certain people, none of whom had anything to do with the project. The amount of the work was minimized, and an attempt to convince the Germans that it was an academic effort and that nothing would come of it. The creeps wanted to say that nothing was being done and that checks at various places had indicated that all potential personnel was being used on other work — I think radar.

Ah, so now this gets really interesting, right? Because this coincides very well with the timing of Heisenberg’s supposed query — apparently originating in Nazi agents in Portugal — regarding whether Dresden would be atomic bombed! (And no, I don’t know why he calls whomever he is talking to “creeps.”)

Obviously I don’t have the whole story here, but the geographical and chronological proximity is a rather impressive overlap, is it not? Could something have gone wrong, or gotten scrambled, in Groves’ attempt to manipulate one of the few German atomic espionage attempts? I.e., Groves had wanted to suggest that the American program was small and unimportant; somebody instead reported back that it was massive and almost ready to go. It seems not impossible, though this is admittedly scant evidence. Either way, it’s clear that Groves would have been mighty mad to find out this question was being asked of Heisenberg.

But, here’s the twist. Arguably the exaggerated outcome would have been (and in fact was!) as good an outcome as Groves’ intended minimization, if not a better one! Heisenberg looked at the six-weeks-to-an-atomic-Dresden claim and said, no way — that doesn’t make any sense. He came away from the whole thing convinced it was just ridiculous wartime nonsense. If the report he had gotten was, “do you believe that the only people working on nuclear fission are a bunch of no-names, instead of Bethe and Fermi and Oppenheimer and Wheeler and all of those other physics luminaries we know the Americans have?,” might that not have raised his suspicions even more?

Of course, that doesn’t explain where Dresden, specifically, would have come into the picture. So there’s still something missing here. And it should be noted that Lisbon was a notorious hub of espionage activity for both sides during the war — so it isn’t necessarily the same guy. So some sobriety intrudes.

Lastly, is it possible the Dresden threat could have been real? The Physikalische Blätter story got picked up by the Washington Post, and they got in touch with Richard G. Hewlett, the Atomic Energy Commission’s official historian. He thought Heisenberg’s story was pretty nuts: “I can’t possibly believe there was an actual threat from the U.S. Government.” This was, obviously, because the US was still a year away from an atomic bomb at the time, and the idea of it being some kind of legitimate, diplomatic threat seems pretty out of character. Though do remember that Roosevelt asked Groves about using the bomb against Germany in December 1944 — so maybe, somewhere, this kind of idea was kicking around inside the heads of some people who knew about the Manhattan Project work but didn’t know how close it was to completion — maybe even someone who was working some kind of diplomatic/espionage backchannel. I don’t know.

As it was, Dresden was of course catastrophically attacked. Over the course of three days in February 1945, some 1,250 Allied heavy bombers pounded the city with incendiaries and high explosives, killing well over 20,000 people and burning the heart out of a city that until that point had been spared the horrors of area bombing. Could Dresden have been kept “pristine” on the theory that it might have been a good atomic bombing target, in the same way that Hiroshima, Nagasaki, Kokura, and Niigata had been? The Physikalische Blätter speculated that maybe this was the case, though there is no evidence that supports this conclusion. I doubt it, personally — the selection of Dresden as a target has its own trajectory that seems independent of any possible atomic narrative, and the idea that it would have been selected as a possible atomic bomb target as early as the summer of 1944 seems rather far-fetched. It should be noted, as well, that the narrative about the atomic bomb in mid-1960s Germany was very much tinged by the Cold War context; it was a common thread of discussion in both the West and the East that the United States would be willing to throw Germany under the bus if it came to a real confrontation with the Soviets.

Still, it’s an interesting constellation of stories: the leak, Heisenberg’s query, and Groves’ attempt at misinformation. If Groves’ misinformation attempt was really did result in the query to Heisenberg, what tremendous irony would abound. Ironic that Groves’ attempt to minimize the effort would result in a exaggerated interpretation; irony that the exaggerated interpretation would lead to total dismissal by the expert.

Tags: 1940s, 1960s, Espionage, Germany, Leaks, Leslie Groves, Manhattan Project, Speculation