The German nuclear programme of World War Two (Part 3)

October 20th, 2016, Published in Articles: Energize


Nuclear power, which may be the cleanest and cheapest technology for the generation of large amounts of reliable electricity to meet the base load requirements of mines and other energy intensive industries, has an interesting history which dates back over 70 years.

The first part of this article discusses the history of the discovery of nuclear fission, while part two shows how the German programme gained some surprising successes, and was actually ahead of the Allies until late 1942.

Unaware of practical applications

“The Germans knew in principle that a bomb could be made, [but] they had no idea how. A detailed theory of the A-bomb had never been developed in Germany and the concentration and separation of U235 was more or less unsuccessfully tried” [13;12].

Paul Rosbaud, the man who wrote, these words, was eminently qualified to do so. The editor of “Naturwissenschaften”, (which published Hahn’s paper on the first splitting of the atom in January 1939 [17]), Rosbaud worked for the German publisher Springer Verlag as a consultant. He also worked as a spy for the British, using his job as a scientific editor to find out what he could about the German military research. Realising the implications of Hahn’s discovery, Rosbaud quietly rushed the article into print, to alert scientists around the world.

The full story of how Rosbaud became a British spy (code named Griffin) is a story in itself. Very briefly, after his Jewish wife and only daughter were sent to Britain for their safety in 1938 [24], Rosbaud was invited to stay in Britain, but decided to return to Germany to work against the Nazis [20]. Even stranger is the true story of how Frank Foley, the station head of British Intelligence (called MI 6) in Berlin, helped Rosbaud’s wife and many others (including thousands of Jews) to escape Nazi Germany [21]. After the war, Rosbaud settled in Britain and founded what eventually became Pergamon Press.

Fig. 1: The last attempt to make a nuclear reactor by the German nuclear programme failed. Here the pile at Haigerloch is being examined by American and British investigators, before being dismantled (Public domain).

Fig. 1: The last attempt to make a nuclear reactor by the German nuclear programme failed. Here the pile at Haigerloch is being examined by American and British investigators, before being dismantled (Public domain).

Rosbaud knew all the nuclear programme members, and managed to get some information out to Britain via Switzerland and the Norwegian underground. It was his information that made the British realise that the German nuclear programme was very far from producing a nuclear bomb. Rosbaud, a trained metallurgist, also recognised that the German nuclear programme was ignorant of many practical details. One of these was something now taken very seriously: nuclear safety.

A startling lack of safety measures

“A startling feature of B-VIII [the last German nuclear experiment], and all the German pile experiments for that matter, was the woeful inadequacy of safety precautions” [2].

German nuclear piles prepared after the disastrous L-IV accident used cast metal uranium, which was less reactive with water. But none of the piles (even the final one prepared at Haigerloch weeks before the end of the war) contained cadmium control rods, which are essential to reducing the risk of a core meltdown: simply by inserting these rods, the chain reaction in a reactor can be brought to an abrupt halt.

Heisenberg’s planning remained casual. He did not realise that a nuclear reactor could cause a thermal runaway (as happened later in Chernobyl), and thought that it was more likely that a natural equilibrium would result [1], as the pile was only a sub-critical experiment [2, 15]. The only emergency provision made was for a single lump of cadmium metal (to absorb excess neutrons), to be dropped into the chimney of the pile in an emergency [2]. Very fortunately, although the German piles produced more neutrons than were supplied, they never “went critical” and generated a self-sustaining chain reaction that could have produced radioactive products [2].

Much of this American and British Intelligence only realised after the end of the war. This came when they were able to secretly listen in and record the conversations of the most important members of the German nuclear programme: particularly, their reactions to the dropping of the atom bombs on Hiroshima and Nagasaki.

Spying at Farm Hall

“Nine of the prominent German scientists who published reports…as members of the Uranverein were picked up by Operation Alsos and incarcerated in England under Operation Epsilon”[9;10].     

As Hitler’s Germany collapsed in April 1945, Russian forces streamed in from the East, while American, British and French forces approached from the West. All the countries wanted to find what they could about the German nuclear programme. Being the most organised, the Americans arranged the biggest operation, called “Alsos”, to round up as many of the key scientists that were working on the nuclear programme before the Russians could get them. The Russians did get some scientists, including Gustav Hertz and Von Ardenne, who they took to Russia and used in their nuclear programme.

Ten scientists (including the nine most important members of the Uranium Club) were interned for six months in Britain, in comfortable circumstances. Their interment at Farm Hall (which had already been used for confidential assignments by British Military Intelligence [1]), was called Operation Epsilon.

Fig. 2: Farm Hall, the country mansion where the key members of the German nuclear programme were interned after World War Two (Public domain).

Fig. 2: Farm Hall, the country mansion where the key members of the German nuclear programme were interned after World War Two (Public domain).

However, none of the men put there realised that microphones had been carefully hidden in the building beforehand to record key conversations on what was then the very latest technology: reusable metal disks with a layer of shellac, similar to old 78 rpm records [1]. Once a week, these conversations were transcribed and translated by British agents, and classified as Top Secret. Copies were made (two for British officials), and one sent first to the American Consulate in London, and then to the United States [1]. There, General Groves, who supervised the Manhattan Project, could study the transcripts and find out what the scientists actually knew about nuclear reactors and the atom bomb. He soon found an answer: not very much. This was particularly evident after the Germans first heard radio news broadcasts (and then read newspaper articles) on the atom bombs dropped on Hiroshima and Nagasaki.

A plan to kill Heisenberg

“If Berg came to the conclusion that the Germans were close [to making an atom bomb], he had orders to shoot Heisenberg”[22].

As scientists at the Manhattan Project began solving the key problems of making plutonium and enriching uranium, more decision makers there began to feel that, surely, the Germans must have managed to solve them as well. By the end of 1944, when the technical details of making actual atom bombs had been largely solved, (and no longer appeared so difficult), more authorities felt, albeit irrationally, that the Germans must be at the same technical level [1]. Because nobody knew for sure exactly what the German nuclear programme had achieved (until the recordings at Farm Hall had been analysed), several strange sounding schemes were put forward. One of the weirdest was to actually kill Heisenberg if it appeared that Germany was close to building an atom bomb.

An opportunity to do this arose in late 1944, when Heisenberg was invited to give some lectures in Geneva and Zurich. Moe Berg, an American baseball player then working for the American Office of Strategic Services (because of his gift for languages), was given the task of attending Heisenberg’s lecture in Zurich, and then shooting him “if anything Heisenberg said convinced him the Germans “were close” [22]. Fortunately for Heisenberg, even Moe Berg, with no background in nuclear physics, judged that the Germans were not close to making an atom bomb [22].

More of Paul Harteck

Dr. Harteck worked [in 1934] in the Cavendish Laboratory in Cambridge, England, with Lord Rutherford and MLE Oliphant”[12]. 

It is ironic that two people who worked in opposing nuclear fission programmes during World War Two (Paul Harteck in the German programme, and Mark Oliphant in the British programme) both worked together in 1933 on something very different: nuclear fusion.

By bombarding deuterium compounds with deuterons, Harteck, Oliphant and Rutherford discovered a new isotope of hydrogen, tritium [12]. More important, they realised the only way this could have happened was that nuclei of deuterium had undergone nuclear fusion [4], something totally unknown till then, and published two papers on this [7, 8, 15].

One would have thought that Paul Harteck, who was responsible for motivating the German nuclear programme, would have disliked the British. In fact, the opposite was true. Harteck thoroughly enjoyed the time he spent in Britain, and was actually happy to be arrested by the British, realising that he had now managed to survive the war [1].

Something of this must have rubbed off on his captors, for he received better treatment when being taken there. He had an infectious sense of humour. When all the German scientists were being flown to Britain to be interned at Farm Hall, Harteck said to the British officer accompanying them that he no longer feared that the aircraft carrying them, a Dakota, would be deliberately crashed to kill them. When asked why, he said that they were in a fine new aircraft, and if they were going to crash, the British would have used a much cheaper aircraft. The British officer, like Harteck, found this very funny [15]. However, Harteck also made far more serious proposal: to use a nuclear reactor to power a submarine.

The nuclear submarine (and the ‘Otto Hahn’)

“When people asked us what use our work was we had to say something that would appeal. I said that it [the uranium machine] surely could be used in a submarine” [15].

Of all the members of the Uranium Club, Paul Harteck was surely the most productive. A few of his achievements include the principle of the ultracentrifuge (later developed by his assistant Wilhelm Groth), an attempt at uranium enrichment (largely unsuccessful), and a method to concentrate heavy water (besides being the leading German expert on heavy water [2]).

But another of his ideas was far head of its time. Harteck realised that, if highly enriched uranium could be produced, a nuclear reactor could be made that was small enough to power a submarine. This topic was deliberately chosen as something that would appeal to a military audience. In fact, one German admiral estimated it would take ten or twenty years [15] to produce a workable nuclear submarine.

As it turned out, the actual time was less. Ten years after the end of the war, the world’s first nuclear-powered submarine, the “Nautilus” was launched. Nearly ten years later, another nuclear-powered ship, the “Otto Hahn”, was launched in 1964. Named after the discoverer of nuclear fission, this ship was an ore carrier.

Harteck was the only one of the group who chose to emigrate to the United States. His expertise on separating the different isotopes of hydrogen [2] and the different isotopes of lithium [16] could well have proved useful to the United States when he began work as a professor at the Rensselaer Polytechnic Institute in New York in 1951, as work was then being done to produce isotopes of these elements (lithium-6, deuterium, and tritium) for the first hydrogen bomb.


[1]  J Bernstein: “Hitler’s uranium club – the secret recodings at Farm Hall”, New York: Springer-Verlag, 2001.
[2]  PF Dahl: “Heavy water and the wartime race for nuclear energy”, Bristol: Institute of Physics Publishing, 1999.
[3]  CM Meyer: “Is Chernobyl dead? Essays on energy: renewable and nuclear”, Muldersdrift: EE Publishers, 2011.
[4]  M Oliphant: “Rutherford: recollections of the Cambridge days”, Amsterdam: Elsevier Publishing Company, 1972.
[5]  M Walker: “Nazi science: myth, truth, and the German atomic bomb”, Cambridge MA: Perseus Publishing, 1995.
[6]  Harris and Paxman: “A higher form of killing: the secret story of gas and germ warfare”, Aylesbury: Triad Granada, 1983.
[7]  ML Oliphant, P Harteck, and Lord Rutherford: “Transmutation effects observed with heavy hydrogen“, Proceedings of the Royal Society, Vol. 144 No. 853, 1934.
[8]  ML Oliphant, P Harteck, and Lord Rutherford: “Transmutation effects observed with heavy hydrogen”, Nature, Vol. 133 No. 3359, 1934.
[9]  Wikipedia: “German nuclear weapon project”,, accessed March 2016.
[10] Wikipedia: “Peenemünde army research center”,, accessed May 2016.[11]  Wikipedia: “Paul Harteck”,, accessed February 2016.
[12]  “Paul Harteck, research scientist”, The New York Times, 24 January, 1985,, accessed March 2016.
[13]  H Kant: “Werner Heisenberg and the German uranium project”, Max Planck Institute for the History of Science, Preprint 203 (2002),, accessed  April 2015.
[14]  P Harteck: “Reich Ministry of War Memorandum 1939 (photocopies)”, Rensselaer Polytechnic Institute, Paul Harteck, 1902-1985. Papers, 1927-1979. Collection MC 17, Box 3, Folder 6.
[15]  P Harteck: “The development of nuclear energy in Germany, 1939-1945”, Edited transcript of taped interview of Dr. Paul Harteck by Professor Joseph J Ermenc, 6 July 1967. Rensselaer Polytechnic Institute, Paul Harteck, 1902-1985. Papers, 1927-1979, Collection MC 17, Box  10, Folder 2.
[16]  P Harteck: “Separation of lithium isotopes”, Rensselaer Polytechnic Institute, Paul Harteck, 1902-1985, Papers, 1927-1979, Collection MC 17, Box 9, Folder 3.
[17]  O Hahn, F Strassmann: “On the detection and characteristics of the alkaline earth metals formed by irradiation or uranium and neutrons” (English translation of German), Naturwissenschaften, Vol. 27 No. 1, January 1939, pp 11-15,, accessed May 2016.
[18]  L Meitner and OR Frisch: “Disintegration of uranium by neutrons: a new type of nuclear reaction”, Nature, Vol 143 (11 February 1939), pp 239-240,, accessed May, 2016.
[19]  Wikipedia: “Gustav Ludwig Hertz”,, accessed May 2016.
[20]  Wikipedia: “Paul Rosbaud”,, accessed May 2016.
[21]  Wikipedia: “Frank Foley”,, accessed May 2016.
[22]  Wikipedia: “Moe Berg”,, accessed May 2016.
[23]  IM Klotz: “Captives of their fantasies: the German atomic bomb scientists”, Journal of Chemical Education, Vol. 74 No.2, Feb 1997, pp 204-209.
[24]  J Simkins: “Paul Rosbaud”. Spartacus Educational,

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