Operation Epsilon.

Review of Dieter Hoffmann (ed.), Operation Epsilon: Die Farm-Hall-Protokolle erstmals vollständig, ergänzt um zeitgenössische Briefe und weitere Dokumente der 1945 in England internierten deutschen Atomforscher, 2nd edn. (Diepholz: GNT-Verlag, 2023), 588 pages, 57 figures, notes, bibliography, index, ISBN 978-3-86225-111-7, 44,80 €.

At the end of the Second World War Allied forces arrested ten German scientists and interned them in a British country house named Farm Hall. Most of these scientists had been connected to the “uranium project,” research into the technical and military applications of nuclear fission. The scientists’ conversations were overheard via hidden microphones, selectively transcribed, translated, and distributed to a few people as secret reports. The original recordings were not saved, and with a few exceptions, the original German conversations were not included.

The Farm Hall transcripts have a long history. They were first used in print by the physicist Samuel Goudsmit in his popular 1947 book Alsos. Goudsmit, who had been part of the Alsos Mission scientific-intelligence gathering mission sent to Europe to find and neutralize any German atomic bomb, argued that the Nazis had ruined German science, with the wartime German uranium project as his main example. Although Goudsmit clearly read and used the transcripts, he did not explicitly reveal their existence.¹ This became clear in 1962 when the former general in charge of the American Manhattan Project, Leslie Groves, quoted from the transcripts in his memoirs.² Indeed Groves appears to have gone out of his way to select some of the most embarrassing and unflattering quotations in order to discredit the German scientists.

When in 1989/1990 this author published his book on the uranium project, a revised version of his dissertation,³ it appeared that the Farm Hall transcripts might never appear. In fact, they were released shortly thereafter in 1992. They quickly appeared in two English-language editions: a straight-forward publication of the transcripts by the British physicist Charles Frank and an extensively annotated version by the American physicist Jeremy Bernstein. Both editions have problems.

In his introduction, Frank argued that “Heisenberg's estimate [at Farm Hall] of the critical mass for a nuclear explosion in ²³⁵U,” which was a “gross overestimate,” was “of crucial importance for determining German nuclear energy policy during the war.” Here Frank subtly misquotes Heisenberg (or at least the transcripts) by writing that “he never worked it out properly,”⁴ when in fact according to the Farm Hall transcripts Heisenberg said: “[…] quite honestly I have never worked it out as I never believed that one could get pure ‘235.’”⁵ Like many other readers of these transcripts, Frank also did not take into account both how shocked and skeptical the scientists initially were.

In contrast to the first publication of the Farm Hall transcripts, Jeremy Bernstein's edition includes extensive commentary, especially with regard to physics. Bernstein approached this work as a physicist doing history rather than a historian of physics. Instead of reconstructing the historical context of Heisenberg's statements and calculations about atomic bombs, for example what Heisenberg had done and said during the war, how far the uranium research had proceeded, what information had been available to him, or what he had been tasked to do, Bernstein simply asked whether the physics was correct, using the high standards of either what the Manhattan Project scientists finally achieved, or current physical knowledge, in order to conclude that the “Germans had no comprehensive understanding of bomb physics.”⁶ Bernstein thereby squandered much of the historical significance of the Farm Hall transcripts. Indeed, the most important evidence for what happened during the war comes from the war, not the subsequent postwar period. Wartime sources make clear that Heisenberg's understanding of the critical mass of an atomic bomb, whatever that was, was in fact not crucial for the development of the uranium project.⁷

The Farm Hall transcripts have also inspired theater. Michael Frayn's award-winning and influential play Copenhagen includes material gleaned from Farm Hall.⁸ The historian of science David Cassidy has both published a play based on Farm Hall and commented on the advantages and disadvantages of this genre for bringing historical events to the general public.⁹

Because with few exceptions the original German dialogue has been lost, the German edition of the Farm Hall transcripts is mostly composed of retranslations of the recorded conversations. Editing and publishing the first edition of this book in 1993 was a controversial, if not courageous thing for an East German scholar to do during the turbulent years immediately following the opening of the Berlin wall and fall of communism. Hoffmann's introduction provides a very good survey of the German wartime work, showing that they understood the essential fundamentals of atomic bombs. Hoffmann's perceptive analysis of the conversations in Farm Hall reveals that, step by step, the scientists moved towards a consensus that would help them navigate the “politics of the past” (Vergangenheitspolitik) in the postwar era, encapsulated by Carl Friedrich von Weizsäcker's argument that they had not wanted to build atomic bombs. Both editions of Operation Epsilon include an extensive 1992 interview with Weizsäcker, which is important and especially interesting because it documents one of the first times that Weizsäcker tried to engage with the work of scholars (including this reviewer) who had called his earlier accounts of the German uranium work into question. The new revised second edition includes a few more passages from Farm Hall as well as over 100 pages of additional valuable historical sources: the diaries of Erich Bagge and Otto Hahn, correspondence from Walther Gerlach, Werner Heisenberg, Max von Laue, and Carl Friedrich von Weizsäcker, and two reports regarding Lise Meitner and the wartime German nuclear research composed by Hahn.

If the transcripts ironically do not reveal much about the uranium research during the war, what do they tell us? The British wardens at Farm Hall detected the lingering effect of National Socialist ideology on the scientists. When the detainees were lent a copy of Life magazine containing articles on the atom bomb and a number of photographs of the scientists who had worked on it, Weizsäcker remarked that naturally most were Germans. For the British commander, Weizsäcker's claim, which was in fact false, demonstrated that the scientists still believed in the master race. Indeed with the possible exception of Max von Laue, he thought that applied to every one of the guests.¹⁰ As Jeremy Bernstein has pointed out, ironically many of the scientists portrayed were in fact Jewish.¹¹ Even Heisenberg made a remarkable comparison between the Allied officials who had interned the Germans and were deciding their fate and some of the most infamous men in the Third Reich. While some officials were extremely friendly towards the German scientists, Heisenberg compared others, who supposedly wanted to keep the Germans locked up in Farm Hall, to Reinhard Heydrich and Ernst Kaltenbrunner, the two men who had served as second-in-command of the SS.¹²

In fact, the scientists interned at Farm Hall expressed very different opinions about the worst excesses of National Socialism. Erich Bagge argued that if the Germans had put people in concentration camps during the war and if Hitler had ordered a few atrocities in concentration camps during the last few years of the conflict, then these excesses had occurred under the stress of war.¹³ In contrast, Karl Wirtz stated flatly that he and his countrymen had done unprecedented things. In Poland the SS had driven up to a girls’ school, brought out the top class and shot them simply because the Polish intelligentsia was to be wiped out. Just imagine, he asked his colleagues, if the Allies had arrived in Hechingen, the small town where many of them had been evacuated during the last years of the war, driven to a girls’ school and shot all the girls!¹⁴ Despite the apparently nationalistic and racist tone immediately after the war, these scientists probably would have been appalled at the scale and depth of the depravity demonstrated by some of their countrymen over the course of the “Euthanasia” program, the war in the east, and the Holocaust.

As Ryan Dahn has perceptively noted: “[…] instead of revealing what Heisenberg and company knew about atomic bombs, when they knew it, and what their intentions were in building them (or not), what they [the transcripts] actually show is how history is processed by humans in real time.”¹⁵ The scientists’ initial reaction to the news of Hiroshima, at a point in time when they had not heard many details about the Allied atomic bomb, was disbelief. The BBC news reports of Hiroshima were not specific and contained very little scientific information. Indeed, much of the confusion found in the Farm Hall transcripts arguably has more to do with the Germans’ lack of information and desperate desire to believe that they had not been completely outdone, than with any lack of scientific or technical understanding on their part. However, as more details gradually trickled in, they were eventually forced to admit that the American-led Manhattan Project had far outstripped their now apparently modest efforts.

The next step these scientists took in dealing with the news was to discuss and debate whether they could have built atomic bombs. Heisenberg argued that the turning point was the spring of 1942, when they were able to convince political authorities that it could be done, with the result that for the first time large funds were made available for their research. However, he added they also would not have had the moral courage to recommend to the government in the spring of 1942 that they should devote 120,000 men to this task.¹⁶ Weizsäcker argued that, even if they had gotten all the support they wanted, it was still not clear that they could have gotten as far as the Americans and British: Even if the Germans had put the same energy into it as the Americans and had wanted it as much as they did, the Americans would have destroyed the German factories. Indeed, Weizsäcker tried to shift the discussion by arguing that what was important was not how far the Germans had gotten, rather the fact that they had been convinced that it could not be completed during the war.

The final stage in the collective construction of a legend for the “German atomic bomb” came when the scientists asked themselves whether or not they had wanted to do it. Early on Wirtz simply stated that he was glad that they did not have it. Weizsäcker took the lead in constructing a consensus, arguing that, instead of making excuses for why they had failed, they should admit that they had not wanted to succeed.¹⁷ Hahn replied that he did not believe that, but was thankful that they had not succeeded. Heisenberg admitted that he had been happy to work on a nuclear reactor instead of a bomb.¹⁸ On the other hand, Bagge subsequently told Kurt Diebner that it was absurd for Weizsäcker to claim that they had not wanted to succeed. While that might have been true for him, it was not for everyone.¹⁹

Let us give the last word to Max von Laue, the only one of the Farm Hall scientists who had not worked on uranium during the war. The letter he wrote to his son in the United States on the day of Hiroshima said: “This first practical application of uranium fission has placed tremendous power in the hands of men. Let God grant that it never falls into anyone but clean hands!”²⁰ If any of the other scientists had said this, then we would find it ironic.