German nuclear weapons program
|German nuclear weapons program|
|Branch||Army Ordnance Office|
Reich Research Council
|Type||Nuclear weapons research|
|Role||development of atomic and radiological weapon|
|Motto(s)||Deutsche Physik (German Physics)|
|Engagements||World War II
|Program Plenipotentiary||Marshal Hermann Göring|
|Minister for Armaments and Ammunition||Albert Speer|
|Uranverein Reichofficer||Walther Gerlach|
|Reichsdirector of the Reichsforschungsrat||Kurt Diebner|
The German nuclear weapons program (German: Uranprojekt; informally known as the Uranverein; English: Uranium Club) was an unsuccessful scientific effort led by Germany to research and develop atomic weapons during World War II. It went through several phases of work, but in the words of a historian, it was ultimately "frozen at the laboratory level" with the "modest goal" to "build a nuclear reactor which could sustain a nuclear fission chain reaction for a significant amount of time and to achieve the complete separation of at least tiny amount of the uranium isotopes." Scholarly consensus is that it failed to achieve these goals.
The first effort started in April 1939, just months after the discovery of nuclear fission in December 1938, but ended only months later shortly ahead of the German invasion of Poland, when many notable physicists were drafted into the Wehrmacht.
A second effort began under the administrative purview of the Wehrmacht's Heereswaffenamt on 1 September 1939, the day of the invasion of Poland. The program eventually expanded into three main efforts: the Uranmaschine (nuclear reactor), uranium and heavy water production, and uranium isotope separation. Eventually it was assessed that nuclear fission would not contribute significantly to ending the war, and in January 1942, the Heereswaffenamt turned the program over to the Reich Research Council (Reichsforschungsrat) while continuing to fund the program. The program was split up among nine major institutes where the directors dominated the research and set their own objectives. Subsequently, the number of scientists working on applied nuclear fission began to diminish, with many applying their talents to more pressing war-time demands.
The most influential people in the Uranverein were Kurt Diebner, Abraham Esau, Walther Gerlach, and Erich Schumann; Schumann was one of the most powerful and influential physicists in Germany. Diebner, throughout the life of the nuclear weapon project, had more control over nuclear fission research than did Walther Bothe, Klaus Clusius, Otto Hahn, Paul Harteck, or Werner Heisenberg. Abraham Esau was appointed as Hermann Göring's plenipotentiary for nuclear physics research in December 1942; Walther Gerlach succeeded him in December 1943.
Politicization of the German academia under the National Socialist regime had driven many physicists, engineers, and mathematicians out of Germany as early as 1933. Those of Jewish heritage who did not leave were quickly purged from German institutions, further thinning the ranks of academia. The politicization of the universities, along with the demands for manpower by the German armed forces (many scientists and technical personnel were conscripted, despite possessing useful skills), substantially reduced the number of able German physicists.
Discovery of nuclear fission
In December 1938, German chemist Otto Hahn and his assistant Fritz Strassmann sent a manuscript to the German science journal Naturwissenschaften ("Natural Sciences") reporting that they had detected and identified the element barium after bombarding uranium with neutrons. Their article was published on 6 January 1939. On 19 December 1938, eighteen days before the publication, Otto Hahn communicated these results and his conclusion of a bursting of the uranium nucleus in a letter to his colleague and friend Lise Meitner, who had fled Germany in July to the Netherlands and then to Sweden. Meitner and her nephew Otto Robert Frisch confirmed Hahn's conclusion of a bursting and correctly interpreted the results as "nuclear fission" – a term coined by Frisch. Frisch confirmed this experimentally on 13 January 1939.
On 22 April 1939, after hearing a colloquium paper by Wilhelm Hanle proposing the use of uranium fission in a Uranmaschine (uranium machine, i.e., nuclear reactor), Georg Joos, along with Hanle, notified Wilhelm Dames, at the Reichserziehungsministerium (REM, Reich Ministry of Education), of potential military applications of nuclear energy. The group included the physicists Walther Bothe, Robert Döpel, Hans Geiger, Wolfgang Gentner (probably sent by Walther Bothe), Wilhelm Hanle, Gerhard Hoffmann, and Georg Joos; Peter Debye was invited, but he did not attend. After this, informal work began at the Georg-August University of Göttingen by Joos, Hanle, and their colleague Reinhold Mannkopff; the group of physicists was known informally as the first Uranverein (Uranium Club) and formally as Arbeitsgemeinschaft für Kernphysik. The group's work was discontinued in August 1939, when the three were called to military training.
Other 1939 initiatives
Paul Harteck was director of the physical chemistry department at the University of Hamburg and an advisor to the Heereswaffenamt (HWA, Army Ordnance Office). On 24 April 1939, along with his teaching assistant Wilhelm Groth, Harteck made contact with the Reichskriegsministerium (RKM, Reich Ministry of War) to alert them to the potential of military applications of nuclear chain reactions. This initiative led, later in the year, to the Second Uranverein. Two days earlier, Joos and Hanle had approached the REM, leading to the First Uranverein.
The industrial firm Auergesellschaft had a substantial amount of "waste" uranium from which it had extracted radium. After reading a June 1939 paper by Siegfried Flügge, on the technical use of nuclear energy from uranium, Nikolaus Riehl, the head of the scientific headquarters at Auergesellschaft, recognized a business opportunity for the company, and in July he went to the HWA (Heereswaffenamt, Army Ordnance Office) to discuss the production of uranium. The HWA was interested and Riehl committed corporate resources to the task. The HWA eventually provided an order for the production of uranium oxide, which took place in the Auergesellschaft plant in Oranienburg, north of Berlin.
The second Uranverein began after the HWA squeezed out the Reichsforschungsrat (RFR, Reich Research Council) of the REM and started the formal German nuclear weapons project under military auspices. This second Uranverein was formed on 1 September 1939, the day World War II began, and had its first meeting on 16 September 1939. The meeting was organized by Kurt Diebner, advisor to the HWA, and held in Berlin. The invitees included Walther Bothe, Siegfried Flügge, Hans Geiger, Otto Hahn, Paul Harteck, Gerhard Hoffmann, Josef Mattauch, and Georg Stetter. A second meeting was held soon thereafter and included Klaus Clusius, Robert Döpel, Werner Heisenberg, and Carl Friedrich von Weizsäcker. Also at this time, the Kaiser-Wilhelm Institut für Physik (KWIP, Kaiser Wilhelm Institute for Physics, after World War II the Max Planck Institute for Physics), in Berlin-Dahlem, was placed under HWA authority, with Diebner as the administrative director, and the military control of the nuclear research commenced.
Heisenberg said in 1939 that the physicists at the (second) meeting said that in principle atomic bombs could be made.... it would take years.... not before five. He said I didn't report it to the Fuehrer until two weeks later and very casually because I did not want the Fuehrer to get so interested that he would order great efforts immediately to make the atomic bomb. Speer felt it was better that the whole thing should be dropped and the Fuehrer also reacted that way. He said they presented the matter in this way for their personal safety as the probability (of success) was nearly zero, but if many thousands (of) people developed nothing, that could have extremely disagreeable consequences for us. So we turned the slogan around to make use of warfare for physics not make use of physics for warfare  Erhard Milch asked how long America would take and was told 1944 though the group between ourselves thought it would take longer, three or four years.
When it was apparent that the nuclear weapon project would not make a decisive contribution to ending the war in the near term, control of the KWIP was returned in January 1942 to its umbrella organization, the Kaiser-Wilhelm Gesellschaft (KWG, Kaiser Wilhelm Society, after World War II the Max-Planck Gesellschaft). HWA control of the project was subsequently passed to the RFR in July 1942. The nuclear weapon project thereafter maintained its kriegswichtig (war importance) designation, and funding continued from the military, but it was then split into the areas of uranium and heavy water production, uranium isotope separation, and the Uranmaschine (uranium machine, i.e., nuclear reactor). It was in effect broken up between institutes where the different directors dominated the research and set their own research agendas. The dominant personnel, facilities, and areas of research were:
- Walther Bothe – Director of the Institut für Physik (Institute for Physics) at the Kaiser-Wilhelm Institut für medizinische Forschung (KWImF, Kaiser Wilhelm Institute for Medical Research, after 1948 the Max-Planck-Institut für medizinische Forschung), in Heidelberg.
- Measurement of nuclear constants. 6 physicists
- Klaus Clusius – Director of the Institute for Physical Chemistry at the Ludwig Maximilian University of Munich
- Kurt Diebner – Director of the HWA Versuchsstelle (testing station) in Gottow and of the RFR experimental station in Stadtilm, Thuringia; he was also an advisor to the HWA on nuclear physics.
- Measurement of nuclear constants. ca. 6 physicists
- Otto Hahn – Director of the Kaiser-Wilhelm-Institut für Chemie (KWIC, Kaiser Wilhelm Institute for Chemistry, after World War II the Max Planck Institut für Chemie – Otto Hahn Institut), in Berlin-Dahlem.
- Transuranic elements, fission products, isotope separation, and measurement of nuclear constants. ca. 6 chemists and physicists
- Paul Harteck – Director of the Physical Chemistry Department of the University of Hamburg.
- Heavy water production and isotope production. 5 physical chemists, physicists, and chemists
- Werner Heisenberg – Director of the Department of Theoretical Physics at the University of Leipzig until summer 1942; thereafter acting director of the Kaiser-Wilhelm-Institut für Physik (Kaiser Wilhelm Institute for Physics), in Berlin-Dahlem.
- Uranmaschine, isotope separation, and measurement of nuclear constants. ca. 7 physicists and physical chemists
- Hans Kopfermann – Director of the Second Experimental Physics Institute at the Georg-August University of Göttingen.
- Isotope separation. 2 physicists
- Nikolaus Riehl – Scientific Director of the Auergesellschaft.
- Uranium production. ca. 3 physicists and physical chemists
- Georg Stetter – Director of the II. Physikalisches Institut (Second Physics Institute) at the University of Vienna.
- Transuranic elements and measurement of nuclear constants. ca. 6 physicists and physical chemists
The point in 1942 when the army relinquished control of the project was its zenith in terms of the number of personnel devoted to the effort, and this was no more than about seventy scientists, with about forty devoting more than half their time to nuclear fission research. After this the number diminished dramatically, and many of those not working with the main institutes stopped working on nuclear fission and devoted their efforts to more pressing war related work.
On 4 June 1942, a conference regarding the project, initiated by Albert Speer as head of the "Reich Ministry for Armament and Ammunition" (RMBM: Reichsministerium für Bewaffnung und Munition; after late 1943 the Reich Ministry for Armament and War Production), decided on its continuation merely for the aim of energy production. On 9 June 1942, Adolf Hitler issued a decree for the reorganization of the RFR as a separate legal entity under the RMBM; the decree appointed Reich Marshal Hermann Göring as its president. The reorganization was done under the initiative of Minister Albert Speer of the RMBM; it was necessary as the RFR under Bernhard Rust the Minister of Science, Education and National Culture was ineffective and was not achieving its purpose. The hope was that Göring would manage the RFR with the same discipline and efficiency as he had the aviation sector. A meeting was held on 6 July 1942 to discuss the function of the RFR and set its agenda. The meeting was a turning point in National Socialism's attitude towards science, as well as recognition that the policies which drove Jewish scientists out of Germany were a mistake, as the Reich needed their expertise. Abraham Esau was appointed on 8 December 1942 as Hermann Göring's Bevollmächtigter (plenipotentiary) for nuclear physics research under the RFR; in December 1943, Esau was replaced by Walther Gerlach. In the final analysis, placing the RFR under Göring's administrative control had little effect on the German nuclear weapon project.
Speer states that the project to develop the atom bomb was scuttled in the autumn of 1942. Though the scientific solution was there, it would have taken all of Germany's production resources to produce a bomb, and then no sooner than 1947. Development did continue with a "uranium motor" for the navy and development of a German cyclotron. However, by the summer of 1943, Speer released the remaining 1200 metric tons of uranium stock for the production of solid-core ammunition.
Over time, the HWA and then the RFR controlled the German nuclear weapon project. The most influential people were Kurt Diebner, Abraham Esau, Walther Gerlach, and Erich Schumann. Schumann was one of the most powerful and influential physicists in Germany. He was director of the Physics Department II at the Frederick William University (later, University of Berlin), which was commissioned and funded by the Oberkommando des Heeres (OKH, Army High Command) to conduct physics research projects. He was also head of the research department of the HWA, assistant secretary of the Science Department of the OKW, and Bevollmächtigter (plenipotentiary) for high explosives. Diebner, throughout the life of the nuclear weapon project, had more control over nuclear fission research than did Walther Bothe, Klaus Clusius, Otto Hahn, Paul Harteck, or Werner Heisenberg.
Paul Peter Ewald, a member of the Uranverein, had proposed an electromagnetic isotope separator, which was thought applicable to 235U production and enrichment. This was picked up by Manfred von Ardenne, who ran a private research establishment.
In 1928, von Ardenne had come into his inheritance with full control as to how it could be spent, and he established his private research laboratory the Forschungslaboratoriums für Elektronenphysik, in Berlin-Lichterfelde, to conduct his own research on radio and television technology and electron microscopy. He financed the laboratory with income he received from his inventions and from contracts with other concerns. For example, his research on nuclear physics and high-frequency technology was financed by the Reichspostministerium (RPM, Reich Postal Ministry), headed by Wilhelm Ohnesorge. Von Ardenne attracted top-notch personnel to work in his facility, such as the nuclear physicist Fritz Houtermans, in 1940. Von Ardenne had also conducted research on isotope separation. Taking Ewald's suggestion he began building a prototype for the RPM. The work was hampered by war shortages and ultimately ended by the war.
The production of heavy water was already under way in Norway when the Germans invaded on 9 April 1940. The Norwegian production facilities for heavy water were quickly secured (though some heavy water had already been removed) and improved by the Germans. The Allies and Norwegians had sabotaged Norwegian heavy water production and destroyed stocks of heavy water by 1943.
Graphite (carbon) as an alternative was not considered as Walther Bothe's neutron absorption coefficient value for carbon was too high; probably due to the boron in the graphite pieces having high neutron absorption.
Reports from the research conducted were published in Kernphysikalische Forschungsberichte (Research Reports in Nuclear Physics), an internal publication of the Uranverein. The reports were classified Top Secret, they had very limited distribution, and the authors were not allowed to keep copies. The reports were confiscated under the Allied Operation Alsos and sent to the United States Atomic Energy Commission for evaluation. In 1971, the reports were declassified and returned to Germany. The reports are available at the Karlsruhe Nuclear Research Center and the American Institute of Physics.
Individual reports are cited on the pages for some of the research participants in the Uranverein; see for example Friedrich Bopp, Kurt Diebner, Klara Döpel, Robert Döpel, Siegfried Flügge, Paul Harteck, Walter Herrmann, Karl-Heinz Höcker, Fritz Houtermans, Horst Korsching, Georg Joos, Heinz Pose, Carl Ramsauer, Fritz Strassmann, Karl Wirtz, and Karl Zimmer.
Two factors which had deleterious effects on the nuclear weapon project were the politicization of the education system under National Socialism and the rise of the Deutsche Physik movement, which was anti-Semitic and had a bias against theoretical physics, especially quantum mechanics.
Adolf Hitler took power on 30 January 1933. On 7 April, the Law for the Restoration of the Professional Civil Service was enacted; this law, and its subsequent related ordinances, politicized the education system in Germany. This had immediate damaging effects on the physics capabilities of Germany. Furthermore, combined with the Deutsche Physik movement, the damaging effects were intensified and prolonged. The consequences to physics in Germany and its subfield of nuclear physics were multifaceted.
An immediate consequence upon passage of the law was that it produced both quantitative and qualitative losses to the physics community. Numerically, it has been estimated that a total of 1,145 university teachers, in all fields, were driven from their posts, which represented about 14% of the higher learning institutional staff members in 1932–1933. Out of 26 German nuclear physicists cited in the literature before 1933, 50% emigrated. Qualitatively, 11 physicists and four chemists who had won or would win the Nobel Prize emigrated from Germany shortly after Hitler came to power, most of them in 1933. These 15 scientists were: Hans Bethe, Felix Bloch, Max Born, Albert Einstein, James Franck, Heinrich Gerhard Kuhn, Peter Debye, Dennis Gabor, Fritz Haber, Gerhard Herzberg, Victor Hess, George de Hevesy, Erwin Schrödinger, Otto Stern, and Eugene Wigner. Britain and the United States were often the recipients of the talent which left Germany. The University of Göttingen had 45 dismissals from the staff of 1932–1933, for a loss of 19%. Eight students, assistants, and colleagues of the Göttingen theoretical physicist Max Born left Europe after Hitler came to power and eventually found work on the Manhattan Project, thus helping the United States, Britain and Canada to develop the atomic bomb; they were Enrico Fermi, James Franck, Maria Goeppert-Mayer, Robert Oppenheimer (who was American, but had studied under Born), Edward Teller, Victor Weisskopf, Eugene Wigner, and John von Neumann. Otto Robert Frisch, who with Rudolf Peierls first calculated the critical mass of U-235 needed for an explosive, was also a Jewish refugee.
Max Planck, the father of quantum theory, had been right in assessing the consequences of National Socialist policies. In 1933, Planck, as president of the Kaiser Wilhelm Gesellschaft (Kaiser Wilhelm Society), met with Adolf Hitler. During the meeting, Planck told Hitler that forcing Jewish scientists to emigrate would mutilate Germany and the benefits of their work would go to foreign countries. Hitler responded with a rant against Jews and Planck could only remain silent and then take his leave. The National Socialist regime would only come around to the same conclusion as Planck in the 6 July 1942 meeting regarding the future agenda of the Reichsforschungsrat (RFR, Reich Research Council), but by then it was too late.
The politicization of the education system essentially replaced academic tradition and excellence with ideological adherence and trappings, such as membership in National Socialist organizations, such as the Nationalsozialistische Deutsche Arbeiterpartei (NSDAP, National Socialist German Workers Party), the Nationalsozialistischer Deutscher Dozentenbund (NSDDB, National Socialist German University Lecturers League), and the Nationalsozialistischer Deutscher Studentenbund (NSDStB, National Socialist German Student League). The politicization can be illustrated with the conflict which evolved when a replacement for Arnold Sommerfeld was sought in view of his emeritus status. The conflict involved one of the prominent Uranverein participants, Werner Heisenberg.
On 1 April 1935 Arnold Sommerfeld, Heisenberg's teacher and doctoral advisor at the University of Munich, achieved emeritus status. However, Sommerfeld stayed on as his own temporary replacement during the selection process for his successor, which took until 1 December 1939. The process was lengthy due to academic and political differences between the Munich Faculty's selection and that of both the Reichserziehungsministerium (REM, Reich Education Ministry) and the supporters of Deutsche Physik. In 1935, the Munich Faculty drew up a candidate list to replace Sommerfeld as ordinarius professor of theoretical physics and head of the Institute for Theoretical Physics at the University of Munich. There were three names on the list: Werner Heisenberg, who received the Nobel Prize in Physics in 1932, Peter Debye, who would receive the Nobel Prize in Chemistry in 1936, and Richard Becker – all former students of Sommerfeld. The Munich Faculty was firmly behind these candidates, with Heisenberg as their first choice. However, supporters of Deutsche Physik and elements in the REM had their own list of candidates and the battle commenced, dragging on for over four years.
During this time, Heisenberg came under vicious attack by the supporters of Deutsche Physik. One such attack was published in Das Schwarze Korps, the newspaper of the Schutzstaffel, or SS, headed by Heinrich Himmler. Heisenberg had been lecturing to his students about the theory of relativity, proposed by the Jewish scientist Albert Einstein. In the editorial, Himmler called Heisenberg a "White Jew" who should be made to "disappear." These verbal attacks were taken seriously, as Jews were subject to physical violence and incarceration at the time. Heisenberg fought back with an editorial and a letter to Himmler, in an attempt to get a resolution to this matter and regain his honour. At one point, Heisenberg's mother visited Himmler's mother to help bring a resolution to the affair. The two women knew each other as a result of Heisenberg's maternal grandfather and Himmler's father being rectors and members of a Bavarian hiking club. Eventually, Himmler settled the Heisenberg affair by sending two letters, one to SS-Gruppenführer Reinhard Heydrich and one to Heisenberg, both on 21 July 1938. In the letter to Heydrich, Himmler said Germany could not afford to lose or silence Heisenberg as he would be useful for teaching a generation of scientists. To Heisenberg, Himmler said the letter came on recommendation of his family and he cautioned Heisenberg to make a distinction between professional physics research results and the personal and political attitudes of the involved scientists. The letter to Heisenberg was signed under the closing "Mit freundlichem Gruss und, Heil Hitler!" ("With friendly greetings and, Heil Hitler!")
Overall, the settlement of the Heisenberg affair was a victory for academic standards and professionalism. However, the replacement of Sommerfeld by Wilhelm Müller on 1 December 1939 was a victory of politics over academic standards. Müller was not a theoretical physicist, had not published in a physics journal, and was not a member of the Deutsche Physikalische Gesellschaft (DPG, German Physical Society); his appointment as a replacement for Sommerfeld was considered a travesty and detrimental to educating a new generation of theoretical physicists.
Missing generation of physicists
Politicization of the academic community, combined with the impact of the Deutsche Physik movement, and other policies such as drafting physicists to fight in the war, had the net effect of bringing about a missing generation of physicists. At the close of the war, physicists born between 1915 and 1925 were almost nonexistent. Those drafted included Uranverein members Paul O. Müller and Karl-Heinz Höcker. Müller died on the Russian front, but Höcker was repatriated in poor health in 1942. They had the classification (uk) not (uk, indispensable) and not even Kurt Diebner, managing director of the KWIP, could stop their call-up. It was not until 1944 that Werner Osenberg, head of the planning board at the Reichsforschungsrat (RFR, Reich Research Council), was able to initiate calling back 5000 engineers and scientists from the front to work on research categorized as kriegsentscheidend (decisive for the war effort). By the end of the war, the number recalled had reached 15,000.
Paul Harteck said at the first meeting of the nuclear physicists that Gustav Hertz should be included "as he was one of the most clever experimenters I know", but he was not "100% Aryan" so could not work for the government (he worked for Siemens). Harteck believed that if Hertz had had a leading position "the first working reactor in the world would have been built in Germany, and perhaps the thermal diffusion process would have been achieved".
Autonomy and accommodation
Members of the Uranverein, Wolfgang Finkelnburg, Werner Heisenberg, Carl Ramsauer, and Carl Friedrich von Weizsäcker were effective in countering the politicization of academia and effectively putting an end to the influence of the Deutsche Physik movement. However, in order to do this they were, as were many scientists, caught between autonomy and accommodation. Essentially, they would have to legitimize the National Socialist system by compromise and collaboration.
During the period in which Deutsche Physik was gaining prominence, a foremost concern of the great majority of scientists was to maintain autonomy against political encroachment. Some of the more established scientists, such as Max von Laue, could demonstrate more autonomy than the younger and less established scientists. This was, in part, due to political organizations, such as the Nationalsozialistischer Deutscher Dozentenbund (National Socialist German University Lecturers League), whose district leaders had a decisive role in the acceptance of an Habilitationsschrift, which was a prerequisite to attaining the rank of Privatdozent necessary to becoming a university lecturer. While some with ability joined such organizations out of tactical career considerations, others with ability and adherence to historical academic standards joined these organizations to moderate their activities. This was the case of Finkelnburg. In mid-1940 Finkelnburg became an acting director of the NSDDB at Technische Hochschule, Darmstadt. As such, he organized the Münchner Religionsgespräche, which took place on 15 November 1940 and was known as the Munich Synod . The Münchner Religionsgespräche was an offensive against deutsche Physik. While the technical outcome may have been thin, it was a political victory against deutsche Physik. Also, in part, it was Finkelnburg's role in organising this event that influenced Carl Ramsauer, as president of the Deutsche Physikalische Gesellschaft, to select Finkelnburg in 1941 as his deputy. Finkelnburg served in this capacity until the end of World War II.
Early in 1942, as president of the DPG, Ramsauer, on Felix Klein's initiative and with the support of Ludwig Prandtl, submitted a petition to Reich Minister Bernhard Rust, at the Reichserziehungsministerium (Reich Education Ministry). The petition, a letter and six attachments, addressed the atrocious state of physics instruction in Germany, which Ramsauer concluded was the result of politicization of education.
Exploitation and denial strategies
Near the end of World War II, the principal Allied war powers each made plans for exploitation of German science. In light of the implications of nuclear weapons, German nuclear fission and related technologies were singled out for special attention. In addition to exploitation, denial of these technologies, their personnel, and related materials to rival allies was a driving force of their efforts. This typically meant getting to these resources first, which to some extent put the Soviets at a disadvantage in some geographic locations easily reached by the Western Allies, even if the area was destined to be in the Soviet zone of occupation by the Potsdam Conference. At times all parties were heavy-handed in their pursuit and denial to others.
The best known US denial and exploitation effort was Operation Paperclip, a broad dragnet that encompassed a wide range of advanced fields, including jet and rocket propulsion, nuclear physics, and other developments with military applications such as infrared technology. Operations directed specifically towards German nuclear fission were Operation Alsos and Operation Epsilon, the latter being done in collaboration with the British. In lieu of the codename for the Soviet operation it is referred to by Oleynikov as the Russian "Alsos".
American and British
Berlin had been a location of many German scientific research facilities. To limit casualties and loss of equipment, many of these facilities were dispersed to other locations in the later years of the war.
Unfortunately for the Soviets, the Kaiser-Wilhelm-Institut für Physik (KWIP, Kaiser Wilhelm Institute for Physics) had mostly been moved in 1943 and 1944 to Hechingen and its neighboring town of Haigerloch, on the edge of the Black Forest, which eventually became the French occupation zone. This move allowed the Americans to take into custody a large number of German scientists associated with nuclear research. The only section of the institute which remained in Berlin was the low-temperature physics section, headed by Ludwig Bewilogua, who was in charge of the exponential uranium pile.
American Alsos teams carrying out Operation BIG raced through Baden-Wurttemburg near the war's end in 1945, uncovering, collecting, and selectively destroying Uranverein elements, including capturing a prototype reactor at Haigerloch and records, heavy water, and uranium ingots at Tailfingen. These were all shipped to the US for study and utilization in the US atomic program.
Nine of the prominent German scientists who published reports in Kernphysikalische Forschungsberichte as members of the Uranverein were picked up by Operation Alsos and incarcerated in England under Operation Epsilon: Erich Bagge, Kurt Diebner, Walther Gerlach, Otto Hahn, Paul Harteck, Werner Heisenberg, Horst Korsching, Carl Friedrich von Weizsäcker, and Karl Wirtz. Also incarcerated was Max von Laue, although he had nothing to do with the nuclear weapon project. Goudsmit, the chief scientific advisor to Operation Alsos, thought von Laue might be beneficial to the postwar rebuilding of Germany and would benefit from the high level contacts he would have in England.
With the interest of the Heereswaffenamt (HWA, Army Ordnance Office), Nikolaus Riehl, and his colleague Günter Wirths, set up an industrial-scale production of high-purity uranium oxide at the Auergesellschaft plant in Oranienburg. Adding to the capabilities in the final stages of metallic uranium production were the strengths of the Degussa corporation's capabilities in metals production.
The Oranienburg plant provided the uranium sheets and cubes for the Uranmaschine experiments conducted at the KWIP and the Versuchsstelle (testing station) of the Heereswaffenamt (Army Ordnance Office) in Gottow. The G-1 experiment performed at the HWA testing station, under the direction of Kurt Diebner, had lattices of 6,800 uranium oxide cubes (about 25 tons), in the nuclear moderator paraffin.
Work of the American Operation Alsos teams, in November 1944, uncovered leads which took them to a company in Paris that handled rare earths and had been taken over by the Auergesellschaft. This, combined with information gathered in the same month through an Alsos team in Strasbourg, confirmed that the Oranienburg plant was involved in the production of uranium and thorium metals. Since the plant was to be in the future Soviet zone of occupation and the Red Army's troops would get there before the Western Allies, General Leslie Groves, commander of the Manhattan Project, recommended to General George Marshall that the plant be destroyed by aerial bombardment, in order to deny its uranium production equipment to the Soviets. On 15 March 1945, 612 B-17 Flying Fortress bombers of the Eighth Air Force dropped 1,506 tons of high-explosive and 178 tons of incendiary bombs on the plant. Riehl visited the site with the Soviets and said that the facility was mostly destroyed. Riehl also recalled long after the war that the Soviets knew precisely why the Americans had bombed the facility—the attack had been directed at them rather than the Germans.
From 1941 to 1947, Fritz Bopp was a staff scientist at the KWIP, and worked with the Uranverein. In 1944, when most of the KWIP was evacuated to Hechingen in Southern Germany due to air raids on Berlin, he went there too, and he was the Institute's Deputy Director there. When the American Alsos Mission evacuated Hechingen and Haigerloch, near the end of World War II, French armed forces occupied Hechingen. Bopp did not get along with them and described the initial French policy objectives towards the KWIP as exploitation, forced evacuation to France, and seizure of documents and equipment. The French occupation policy was not qualitatively different from that of the American and Soviet occupation forces, it was just carried out on a smaller scale. In order to put pressure on Bopp to evacuate the KWIP to France, the French Naval Commission imprisoned him for five days and threatened him with further imprisonment if he did not cooperate in the evacuation. During his imprisonment, the spectroscopist Hermann Schüler, who had a better relationship with the French, persuaded the French to appoint him as Deputy Director of the KWIP. This incident caused tension between the physicists and spectroscopists at the KWIP and within its umbrella organization the Kaiser-Wilhelm Gesellschaft (Kaiser Wilhelm Society).
At the close of World War II, the Soviet Union had special search teams operating in Austria and Germany, especially in Berlin, to identify and "requisition" equipment, material, intellectual property, and personnel useful to the Soviet atomic bomb project. The exploitation teams were under the Soviet Alsos and they were headed by Lavrentij Beria's deputy, Colonel General A. P. Zavenyagin. These teams were composed of scientific staff members, in NKVD officer's uniforms, from the bomb project's only laboratory, Laboratory No. 2, in Moscow, and included Yulij Borisovich Khariton, Isaak Konstantinovich Kikoin, and Lev Andreevich Artsimovich. Georgij Nikolaevich Flerov had arrived earlier, although Kikoin did not recall a vanguard group. Targets on the top of their list were the Kaiser-Wilhelm Institut für Physik (KWIP, Kaiser Wilhelm Institute for Physics), the Frederick William University (today, the University of Berlin), and the Technische Hochschule Berlin (today, the Technische Universität Berlin (Technical University of Berlin).
German physicists who worked on the Uranverein and were sent to the Soviet Union to work on the Soviet atomic bomb project included: Werner Czulius, Robert Döpel, Walter Herrmann, Heinz Pose, Ernst Rexer, Nikolaus Riehl, and Karl Zimmer. Günter Wirths, while not a member of the Uranverein, worked for Riehl at the Auergesellschaft on reactor-grade uranium production and was also sent to the Soviet Union.
Zimmer's path to work on the Soviet atomic bomb project was through a prisoner of war camp in Krasnogorsk, as was that of his colleagues Hans-Joachim Born and Alexander Catsch from the Kaiser-Wilhelm Institut für Hirnforschung (KWIH, Kaiser Wilhelm Institute for Brain Research, today the Max-Planck-Institut für Hirnforschung), who worked there for N. V. Timofeev-Resovskij, director of the Abteilung für Experimentelle Genetik (Department of Experimental Genetics). All four eventually worked for Riehl in the Soviet Union at Laboratory B in Sungul'.
Von Ardenne, who had worked on isotope separation for the Reichspostministerium (Reich Postal Ministry), was also sent to the Soviet Union to work on their atomic bomb project, along with Gustav Hertz, Nobel laureate and director of Research Laboratory II at Siemens, Peter Adolf Thiessen, director of the Kaiser-Wilhelm Institut für physikalische Chemie und Elektrochemie (KWIPC, Kaiser Wilhelm Institute for Chemistry and Electrochemisty, today the Fritz Haber Institute of the Max-Planck Society), and Max Volmer, director of the Physical Chemistry Institute at the Berlin Technische Hochschule (Technical University of Berlin), who all had made a pact that whoever first made contact with the Soviets would speak for the rest. Before the end of World War II, Thiessen, a member of the Nazi Party, had Communist contacts. On 27 April 1945, Thiessen arrived at von Ardenne's institute in an armored vehicle with a major of the Soviet Army, who was also a leading Soviet chemist, and they issued Ardenne a protective letter (Schutzbrief).
Comparison of the Manhattan Project and the Uranverein
The United States, British, and Canadian governments worked together to create the Manhattan Project that developed the uranium and plutonium atomic bombs. Its success has been attributed[by whom?] to meeting all four of the following conditions:
- A strong initial drive, by a small group of scientists, to launch the project.
- Unconditional government support from a certain point in time.
- Essentially unlimited manpower and industrial resources.
- A concentration of brilliant scientists devoted to the project.
Even with all four of these conditions in place the Manhattan Project succeeded only after the war in Europe had been brought to a conclusion.
For the Manhattan Project, the second condition was met on 9 October 1941 or shortly thereafter. Germany for a long time was thought to have fallen short of what was required to make an atomic bomb. Mutual distrust existed between the German government and some scientists. By the end of 1941 it was already apparent that the German nuclear weapon project would not make a decisive contribution to ending the German war effort in the near term, and control of the project was relinquished by the Heereswaffenamt (HWA, Army Ordnance Office) to the Reichsforschungsrat (RFR, Reich Research Council) in July 1942.
As to condition four, the high priority allocated to the Manhattan Project allowed for the recruitment and concentration of capable scientists on the project. In Germany, on the other hand, a great many young scientists and technicians who would have been of great use to such a project were conscripted into the German armed forces, while others had fled the country before the war due to antisemitism and political persecution.
Whereas Enrico Fermi, a scientific Manhattan leader, had a "unique double aptitude for theoretical and experimental work" in the 20th century, the successes at Leipzig until 1942 resulted from the cooperation between the theoretical physicist Werner Heisenberg and the experimentalist Robert Döpel. Most important was their experimental proof of an effective neutron increase in April 1942. At the end of July of the same year, the group around Fermi also succeeded in the neutron increase within a reactor-like arrangement.
In June 1942, some six months before the American Chicago Pile-1 achieved man-made criticality for the first time anywhere, Döpel's "Uran-Maschine" was destroyed by a chemical explosion introduced by oxygen, which finished the work on this topic at Leipzig. Thereafter, despite increased expenditures the Berlin groups and their extern branches didn't succeed in getting a reactor critical until the end of World War II. However, this was realized by the Fermi group in December 1942, so that the German advantage was definitively lost, even with respect to research on energy production.
German historian Klaus Hentschel summarizes the organizational differences as:
- Compared with the British and American war research efforts united in the Manhattan Project, to this day the prime example of 'big science," the Uranverein was only a loosely knit, decentralized network of researchers with quite different research agendas. Rather than teamwork as on the American end, on the German side we find cut-throat competition, personal rivalries, and fighting over the limited resources.
In terms of financial and human resources, the comparisons between the Manhattan Project and the Uranverein are stark. The Manhattan Project consumed some US$2 billion (1945) in government funds, and employed at its peak some 120,000 people, mostly in the sectors of construction and operations. Total, the Manhattan Project involved the labor of some 500,000 people, nearly 1% of the entire US civilian labor force. By comparison, the Uranverein was budgeted a mere 8 million reichsmarks, equivalent to about US$2 million (1945) — a factor of 1,000 less.
Controversies regarding alleged nuclear tests
In a 2005 book, Hitlers Bombe, Rainer Karlsch claimed to have located, in the archives of the former KGB in Moscow, Heisenberg's speech notes from the Harnack Haus conference of July 1942, revealing that Heisenberg was a strong advocate for development of a German nuclear weapon.[page needed]
Karlsch alleged that Diebner's team conducted the first successful nuclear weapon test, of some type of nuclear-related device employing hollow charges for ignition, in Ohrdruf, Thuringia, on 4 March 1945,[page needed] allegedly not far from the concentration camp there. Karlsch quoted a purported eyewitness named Clare Werner, who claimed to have been standing on a hillside in Thuringia at the time of the test:
Not too far away was the military training base near the town of Ohrdruf. Unexpectedly there was a flash of light. "I suddenly saw something,' she said ... "it was as bright as hundreds of bolts of lightning, red on the inside and yellow on the outside, so bright you could've read the newspaper. It all happened so quickly, and then we couldn't see anything at all. We just noticed there was a powerful wind ..."[page needed]
Karlsch has acknowledged that he lacked "absolute proof" for his claims, remaining "defiant", and said he hoped his book would provoke further research. Other sources cited by Karlsch refer to a previous event on the northeastern German coastal island of Rügen in the Baltic Sea, just off Stralsund, in late 1944.
Science historian Mark Walker also published his analysis[vague] in 2005. In 2005 Karlsch and Walker published an article on the controversial historical evidence.[further explanation needed] In 2006 the Physikalisch-Technische Bundesanstalt (PTB; "Federal Institute for Physics Technology") concluded tests of soil samples from the area of the alleged test in Thuringia, summarizing the results in the phrase kein Befund ("nothing found").
Former Luftwaffe pilot Hans Zinsser claimed he witnessed a nuclear-like explosion while flying near Ludwigslust in late 1944. While patrolling in a Heinkel He 111, Zinsser claimed he was looking at a map when his cockpit was illuminated by a blinding white light. He then claimed to see a giant mushroom cloud rising into the sky before his plane was hit by a shockwave. In a newspaper, he claimed:
"In early October 1944 I flew away 12-15 km from a nuclear test station near Ludwigslust (south of Lübeck). A cloud shaped like a mushroom with turbulent, billowing sections (at about 7000 metres) stood, without any seeming connections over the spot where the explosion took place. Strong electrical disturbances and the impossibility to continue radio communication as by lighting turned up."
- Due to the surrender of Germany. The program effort ceased due to the Fall of Berlin.
- Walker 1995, 198-199.
- Judt, Matthias; Burghard Ciesla (1996). Technology transfer out of Germany after 1945. Routledge. p. 55. ISBN 978-3-7186-5822-0.
- O. Hahn and F. Strassmann Über den Nachweis und das Verhalten der bei der Bestrahlung des Urans mittels Neutronen entstehenden Erdalkalimetalle (On the detection and characteristics of the alkaline earth metals formed by irradiation of uranium with neutrons), Naturwissenschaften Volume 27, Number 1, 11–15 (1939). The authors were identified as associated with the Kaiser-Wilhelm-Institut für Chemie, Berlin-Dahlem. Received 22 December 1938.
- Ruth Lewin Sime Lise Meitner's Escape from Germany, American Journal of Physics Volume 58, Number 3, 263–267 (1990).
- Lise Meitner and O. R. Frisch Disintegration of Uranium by Neutrons: a New Type of Nuclear Reaction, Nature, Volume 143, Number 3615, 239–240 (11 February 1939). The paper is dated 16 January 1939. Meitner is identified as being at the Physical Institute, Academy of Sciences, Stockholm. Frisch is identified as being at the Institute of Theoretical Physics, University of Copenhagen.
- O. R. Frisch Physical Evidence for the Division of Heavy Nuclei under Neutron Bombardment, Nature, Volume 143, Number 3616, 276–276 (18 February 1939) Archived 23 January 2009 at the Wayback Machine. The paper is dated 17 January 1939. [The experiment for this letter to the editor was conducted on 13 January 1939; see Richard Rhodes, The Making of the Atomic Bomb 263 and 268 (Simon and Schuster, 1986).]
- In 1944 Hahn received the Nobel Prize for Chemistry for the discovery and the radiochemical proof of nuclear fission. Some American historians have documented their view of the history of the discovery of nuclear fission and believe Meitner should have been awarded the Nobel Prize with Hahn. See the following references: Ruth Lewin Sime From Exceptional Prominence to Prominent Exception: Lise Meitner at the Kaiser Wilhelm Institute for Chemistry Ergebnisse 24 Forschungsprogramm Geschichte der Kaiser-Wilhelm-Gesellschaft im Nationalsozialismus (2005); Ruth Lewin Sime Lise Meitner: A Life in Physics (University of California, 1997); and Elisabeth Crawford, Ruth Lewin Sime, and Mark Walker A Nobel Tale of Postwar Injustice, Physics Today Volume 50, Issue 9, 26–32 (1997).
- Kant, 2002, Reference 8 on p. 3.
- Hentschel and Hentschel, 1996, 363–364 and Appendix F; see the entries for Esau, Harteck and Joos. See also the entry for the KWIP in Appendix A and the entry for the HWA in Appendix B.
- Macrakis, 1993, 164–169.
- Mehra and Rechenberg, Volume 6, Part 2, 2001, 1010–1011.
- Siegfried Flügge Kann der Energieinhalt der Atomkerne technisch nutzbar gemacht werden?, Die Naturwissenschaften Volume 27, Issues 23/24, 402–10 (9 June 1939).
- Also see: Siegfried Flügge Die Ausnutzung der Atomenergie. Vom Laboratoriumsversuch zur Uranmaschine – Forschungsergebnisse in Dahlem, Deutsche Allgemeine Zeitung No. 387, Supplement (15 August 1939). English translation: Document No. 74 Siegfried Flügge: Exploiting Atomic Energy. From the Laboratory Experiment to the Uranium Machine – Research Results in Dahlem [15 August 1939] in Hentschel, Klaus (Editor) and Ann M. Hentschel (Editorial Assistant and Translator) Physics and National Socialism: An Anthology of Primary Sources (Birkhäuser, 1996) pp. 197–206. [This article is Flügge's popularized version of the June 1939 article in Die Naturwissenschaften.]
- Hentschel and Hentschel, 1996, 369, Appendix F, see the entry for Riehl, and Appendix D, see the entry for Auergesellschaft.
- Riehl and Seitz, 1996, 13.
- Hentschel and Hentschel, 1996, 363–364 and Appendix F; see the entries for Diebner and Döpel. See also the entry for the KWIP in Appendix A and the entry for the HWA in Appendix B.
- Ermenc 1989, p. 34. sfn error: no target: CITEREFErmenc1989 (help)
- Ermenc 1989, p. 23. sfn error: no target: CITEREFErmenc1989 (help)
- Ermenc 1989, p. 27. sfn error: no target: CITEREFErmenc1989 (help)
- Hentschel and Hentschel, 1996; see the entry for the KWIP in Appendix A and the entries for the HWA and the RFR in Appendix B. Also see p. 372 and footnote No. 50 on p. 372.
- Walker, 1993, 49–53.
- Walker, 1993, 52–53.
- Kant, 2002, 19.
- Deutsches Museum "Geheimdokumente zu den Forschungszentren": Gottow, Hamburg, Berlin, Leipzig und Wien, Heidelberg, Straßburg
- Walker, 1993, 52 and Reference No. 40 on p. 262.
- Wilhelm Hanle and Helmut Rechenberg 1982: Jubiläumsjahr der Kernspaltungs¬forschung. Physikalische Blätter 38 (1982) Nr. 12, S. 365–367.
- Document 98: The Führer's Decree on the Reich Research Council, 9 June 1942, in Hentschel an Hentschel, 1996, 303.
- Read Samuel Goudsmit's account and interpretation of the role of the RFR in Document 111: War Physics in Germany, January 1946, in Hentschel and Hentschel, 1996, 345–352.
- Document 99: Record of Conference Regarding the Reich Research Council, 6 July 1942, in Hentschel and Hentschel, 1996, 304–308.
- Macrakis, 1993, 91–94.
- Hentschel and Hentschel, 1996, Appendix F; see the entries for Esau and Gerlach.
- Walker, 1993, 86.
- Speer, Albert (1995). Inside the Third Reich. London: Weidenfeld & Nicolson. pp. 314–320. ISBN 9781842127353.
- Speer, pages 314–320
- Walker, 1993, 208.
- Hentschel and Hentschel, 1996, Appendix F; see the entry for Schumann. Also see footnote No. 1 on p. 207.
- sachen.de Archived 25 March 2008 at the Wayback Machine –Zur Ehrung von Manfred von Ardenne.
- Ardenne – Deutsches Historisches Museum.
- Hentschel and Hentschel, 1996, Appendix F; see entry for Ardenne. Also see the entry for the Reichspostministerium in Appendix C.
- Walker, 1993, 83–84, 170, 183, and Reference No. 85 on p. 247. See also Manfred von Ardenne Erinnerungen, fortgeschrieben. Ein Forscherleben im Jahrhudert des Wandels der Wissenschaften und politischen Systeme. (Droste, 1997).
- Bethe, Hans A. (2000). "The German Uranium Project". Physics Today. 53 (7): 34–36. Bibcode:2000PhT....53g..34B. doi:10.1063/1.1292473.
- Hentschel and Hentschel, 1996, Appendix E; see the entry for Kernphysikalische Forschungsberichte.
- Walker, 1993, 268–274.
- Beyerchen, 1977, 123–140.
- Beyerchen, 1977, 44.
- Hentschel and Hentschel, 1996, lviii.
- Beyerchen, 1977, 48.
- Helge Krgah: Generations: A History of Physics in the Twentieth Century (Princeton, 1999) 249–256.
- An Italian working in Rome, Fermi left after anti-semitic policies were introduced in Italy
- The eight students, assistants, and colleagues of the theoretical physicist Max Born who left Europe found work on the Manhattan Project were:
- Enrico Fermi – Director of Research, Met Lab of the University of Chicago – One of the four major sites of the Manhattan Engineering District.
- James Franck – Director of the Chemistry Division, Met Lab
- Maria Goeppert-Mayer – Worked on the Manhattan Project with Harold Urey at Columbia University on isotope separation.
- Robert Oppenheimer – Director of Los Alamos Scientific Laboratory (LASL) – One of the four major sites of the Manhattan Engineering District.
- Edward Teller – Head of T-1 Group, Hydrodynamics of Implosion and Super, LASL
- Victor Weisskopf – Head of T-3 Group, Experiments, Efficiency Calculations, and Radiation Hydrodynamics, LASL
- Eugene Wigner – Director of Theoretical Studies, Met Lab
- John von Neumann – LASL consultant on implosion mechanism for the plutonium bomb. (Neumann was assistant to David Hilbert at Göttingen and was greatly influenced by both David Hilbert's and Max Born's work. Neumann applied the mathematics of Hilbert space to Born's quantum mechanics, and, in 1932, his foundational book on the mathematical underpinnings of quantum mechanics, Mathematische Grundlagen der Quantenmechanik, was published.)
- Document 114: Max Planck: My Audience with Adolf Hitler in Hentschel and Hentschel, 1996, 359–261.
- Klaus Hentschel (Editor) and Ann M. Hentschel (Editorial Assistant and Translator) Physics and National Socialism: An Anthology of Primary Sources (Birkhäuser, 1996). In this book, see: Document No. 55 'White Jews' in Science [15 July 1937] pp. 152–157.
- Goudsmit, Samuel A. ALSOS (Tomash Publishers, 1986) pp. 117–119.
- Alan D. Beyerchen, Scientists Under Hitler: Politics and the Physics Community in the Third Reich (Yale, 1977) pp. 153–167.
- David C. Cassidy Uncertainty: The Life and Science of Werner Heisenberg (W. H. Freeman and Company, 1992) pp. 383–387.
- Powers, Thomas Heisenberg's War: The Secret History of the German Bomb (Knopf, 1993) pp 40–43.
- Klaus Hentschel (Editor) and Ann M. Hentschel (Editorial Assistant and Translator) Physics and National Socialism: An Anthology of Primary Sources (Birkhäuser, 1996). In this book, see: Document No. 55 'White Jews' in Science [15 July 1937] pp. 152–157; Document No. 63 Heinrich Himmler: Letter to Reinhard Heydrich [21 July 1938] pp. 175–176; Document No. 64 Heinrich Himmler: Letter to Werner Heisenberg [21 July 1938] pp. 176–177; Document No. 85 Ludwig Prandtl: Attachment to the letter to Reich Marschal (sic) Hermann Göring [28 April 1941] pp. 261–266; and Document No. 93 Carl Ramsauer: The Munich Conciliation and Pacification Attempt 20 January 1942 pp. 290–292.
- Walker, 1993, pp. 42–43, 80.
- see articles on Paul O. Müller and Karl-Heinz Höcker
- Ermenc 1989, pp. 112,113. sfn error: no target: CITEREFErmenc1989 (help)
- Dieter Hoffmann Between Autonomy and Accommodation: The German Physical Society during the Third Reich, Physics in Perspective 7(3) 293–329 (2005).
- Walker, 1993, 80.
- Beyerchen, 1977, 199–210.
- Hoffmann, 2005, 293–329.
- Hentschel and Hentschel, 1996, Appendix C; see the entry for the NSDDB.
- Beyerchen, 1977, 176–179.
- Hentschel and Hentschel, 1996, 341–342.
- Hentschel and Hentschel, 1996, 290.
- Finkelnburg invited five representatives to make arguments for theoretical physics and academic decisions based on ability, rather than politics: Carl Friedrich von Weizsäcker, Otto Scherzer, Georg Joos, Otto Heckmann, and Hans Kopfermann. Alfons Bühl, a supporter of deutsche Physik, invited Harald Volkmann, Bruno Thüring, Wilhelm Müller, Rudolf Tomaschek, and Ludwig Wesch. The discussion was led by Gustav Borer, with Herbert Stuart and Johannes Malsch as observers. See Document 110: The Fight against Party Politics by Wolfgang Finkelnburg in Hentschel and Hentschel, 1996, 339–345. Also see Beyerchen, 1977, 176–179.
- Document 86: Letter to Ludwig Prandtl by Carl Ramsauer, 4 June 1944, in Hentschel and Hentschel, 1996, 267–268.
- Letter to Bernhard Rust, 20 January 1942. Document # 90 in Hentschel and Hentschel, 1996, pp. 278–281.
- Attachment I: American Physics Outdoes German Physics. Document No. 91 in Hentschel and Hentschel, 1996, pp. 281–284.
- Attachment II: Publications Against Modern Theoretical Physics. Cited in Hentschel and Hentschel, 1996, p. 279, but omitted from the anthology.
- Attachment III: The Crucial Importance of Theoretical Physics and Particularly Modern Theoretical Physics. Cited in Hentschel and Hentschel, 1996, p. 280, but omitted from the anthology.
- Attachment IV: Refuting Allegations that Modern Theoretical Physics is a Product of the Jewish Spirit. Document 92 in Hentschel and Hentschel, 1996, pp. 290–292.
- Attachment V: Excerpt from an attachment to Ludwig Prandtl's letter to Reich Marshal Hermann Göring, 28 April 1941. Cited in Hentschel and Hentschel, 1996, 280; see Document No. 85 in Hentschel and Hentschel, 1996, pp. 261–266.
- Attachment VI: The Munich Conciliation and Pacification Attempt. Document No. 93 in Hentschel and Hentschel, 1996, pp. 290–292.
- Hentschel and Hentschel, 1966, Appendix F; see the entry for Carl Ramsauer.
- Gimbel, John U.S. Policy and German Scientists: The Early Cold War, Political Science Quarterly Volume 101, Number 3, 433–451 (1986).
- Gimbel, John Science, Technology, and Reparations: Exploitation and Plunder in Postwar Germany (Stanford, 1990).
- Goudsmit, Samuel with an introduction by R. V. Jones Alsos (Toamsh, 1986).
- Norman M. Naimark The Russians in Germany: A History of the Soviet Zone of Occupation, 1945–1949 (Belkanp, 1995).
- Oleynikov, Pavel V. German Scientists in the Soviet Atomic Project, The Nonproliferation Review Volume 7, Number 2, 1–30 (2000).
- Oleynikov, 2000, 3.
- Naimark, 1995, 208–209.
- Bernstein, 2001, 49–52.
- Beck, Alfred M, et al, United States Army in World War II: The Technical Services – The Corps of Engineers: The War Against Germany, 1985 Chapter 24, Into the Heart of Germany
- Walker, 1993, 268–274 and Reference No. 40 on p. 262.
- Bernstein, 2001, 50 and 363–365.
- Hentschel and Hentschel, 1996, 369, Appendix F (see the entry for Nikolaus Riehl), and Appendix D (see the entry for Auergesellschaft).
- Riehl and Seitz, 1996, 13 and 69.
- F. Berkei, W. Borrmann, W. Czulius, Kurt Diebner, Georg Hartwig, K. H. Höcker, W. Herrmann, H. Pose, and Ernst Rexer Bericht über einen Würfelversuch mit Uranoxyd und Paraffin G-125 (dated before 26 November 1942).
- Hentschel and Hentschel, 1996, 369 and 373, Appendix F (see the entry for Nikolaus Riehl and Kurt Diebner), and Appendix D (see the entry for Auergesellschaft).
- Bernstein, 2001, 50–51.
- Naimark, 1995, 205–207.
- Riehl and Seitz, 1996, 77–79.
- Walker, 1993, 156.
- Leslie M. Groves Now it Can be Told: The Story of the Manhattan Project (De Capo, 1962) 220–222 and 230–231.
- Hentschel and Hentschel, 1996, Appendix F; see the entry for Bopp.
- Walker, 1993, 186–187.
- Bernstein, 2001, 212 and footnote No. 5 on p. 212.
- For information on the American and Russian exploitation of Germany after World War II, see: Norman M. Naimark The Russians in Germany: A History of the Soviet Zone of Occupation, 1945–1949 (Belknap, 1995); John Gimbel Science, Technology, and Reparations: Exploitation and Plunder in Postwar Germany (Stanford University Press, 1990); and John Gimbel U.S. Policy and German Scientists: The Early Cold War, Political Science Quarterly Volume 101, Number 3, 433–451 (1986).
- Oleynikov, 2000, 3–8.
- Riehl and Seitz, 1996, 71–83.
- Norman M. Naimark The Soviets in Germany: A History of the Soviet Zone of Occupation, 1945–1949 (Belkanp, 1995) 203–250.
- Riehl and Seitz, 1996, 121–132.
- Oleynikov, 2000, 11 and 15–17.
- Heinemann-Grüder, Andreas Keinerlei Untergang: German Armaments Engineers during the Second World War and in the Service of the Victorious Powers in Monika Renneberg and Mark Walker (editors) Science, Technology and National Socialism 30–50 (Cambridge, 2002 paperback edition) 44.
- Hentschel and Hentschel, 1996, Appendix F; see the entry for Thiessen.
- Oleynikov, 2000, 5 and 11–13.
- N. P. Landsman, Getting even with Heisenberg, Studies in History and Philosophy of Modern Physics Volume 33, 297–325 (2002) pp. 318–319.
- Landsman, 2002, 303 and 319–319.
- Jeremy Bernstein Hitler's Uranium Club: The Secret Recording's at Farm Hall (Copernicus, 2001) 122–123.
- M. Bundy Danger and survival: Choices about the bomb in the first fifty years (Random House, 1988), as cited in Landsman, 2002, 318 n83.
- "Radioactive find points to 'success' of Nazi atomic bomb program". NewsComAu. Retrieved 5 November 2017.
- Wilhelm Hanle, Memoiren. I. Physikalisches Institut, Justus-Liebig-Universität, 1989.
- Heinrich Arnold, Robert Döpel and his Model of Global Warming. (2011) p. 27.
- Mangravite, Andrew (2015). "Magical Thinking". Distillations. 1 (4): 44–45. Retrieved 22 March 2018.
- Ball, Philip (2014). Serving the Reich : the struggle for the soul of physics under Hitler. Chicago: University of Chicago Press. ISBN 978-0226204574.
- Van der Vat, Dan; Albert Speer (1997). The Good Nazi: The Life and Lies of Albert Speer. Houghton Mifflin Harcourt. p. 138. ISBN 978-0-395-65243-5.
- Wilhelm Hanle and Helmut Rechenberg 1982, Jubiläumsjahr der Kernspaltungsforschung. Physikalische Blätter 38 (1982) Nr. 12, p. 367.
- Robert and Klara Döpel, Werner Heisenberg, Der experimentelle Nachweis der effektiven Neutronenvermehrung in einem Kugel-Schichten-System aus D2O und Uran-Metall. Facsimile: Forschungszentren/Leipzig/Neutronenvermehrung (1942). Published 1946 in: Heisenberg, W., Collected Works Vol. A II (Eds. W. Blum, H.-P Dürr and H. Rechenberg, Berlin etc. (1989), pp. 536–544.
- D. J. C. Irving, The Virus House. London 1967. Paperback (with the text unchanged): The German Atomic Bomb. The History of Nuclear Research in Nazi Germany. New York 1983. The relevant statement in the epilog reads as follows: "Indeed, the Germans were the first physicists in the world, with their Leipzig pile L-IV, to achieve positive neutron production, in the first half of 1942."
- This was the first accident that disrupted a nuclear energy assembly; cf. Reinhard Steffler, Reaktorunfälle und die Handlungen der Feuerwehr: Leipzig, Tschernobyl und Fukushima – eine erste Analyse. Elbe-Dnjepr-Verlag Leipzig-Mockrehna 2011. ISBN 3-940541-33-8.
- Hentschel and Hentschel, lxviii.
- Wellerstein, Alex (1 November 2013). "How many people worked on the Manhattan Project?". Restricted Data. Archived from the original on 21 July 2019. Retrieved 16 November 2019.
- Hentschel and Hentschel, 1996, lxix.
- Karlsch, Rainer, 2005, Hitler's Bombe
- "Spurensuche in der "Hölle von Ohrdruf" (German)". Ostthüringer Zeitung. 9 April 2010. Retrieved 6 August 2014.
- Furlong, Ray (14 March 2005). "Hitler 'tested small atom bomb'". BBC News.
- "The Third Reich: How Close Was Hitler to the A-Bomb?". Spiegel Online. Retrieved 13 March 2016.
- Walker, Mark (2005). "Eine Waffenschmiede? Kernwaffen- und Reaktorforschung am Kaiser-Wilhelm-Institut für Physik (Ergebnisse 26)" (PDF). Forschungsprogramm „Geschichte der Kaiser-Wilhelm-Gesellschaft im Nationalsozialismus".
- Karlsch, Rainer; Walker, Mark (1 June 2005). "New light on Hitler's bomb". physicsworld.com. Retrieved 1 October 2019.
- Herbert Janßen and Dirk Arnold In Bodenproben keine Spur von "Hitlers Bombe": PTB legt Analysebericht zu Bodenproben aus dem thüringischen Ohrdruf vor, Physikalisch-Technische Bundesanstalt press release (15 February 2006) Archived 18 August 2016 at the Wayback Machine.
- Was there a nuclear explosion in Germany during WW2?
- The New York Nuke | Mysteries of the Third Reich Part Three on Youtube
- Ball, Philip (2014). Serving the Reich : the struggle for the soul of physics under Hitler. Chicago: University of Chicago Press. ISBN 978-0226204574.
- Bernstein, Jeremy Hitler's Uranium Club: The Secret Recordings at Farm Hall (Copernicus, 2001) ISBN 0-387-95089-3
- Bernstein, Jeremy Heisenberg and the critical mass, Am. J. Phys. Volume 70, Number 9, 911–916 (2002)
- Bernstein, Jeremy Heisenberg in Poland, Am. J. Phys. Volume 72, Number 3, 300–304 (2004). See also Letters to the Editor by Klaus Gottstein and a reply by Jeremy Bernstein in Am. J. Phys. Volume 72, Number 9, 1143–1145 (2004).
- Beyerchen, Alan D. Scientists Under Hitler: Politics and the Physics Community in the Third Reich (Yale, 1977) ISBN 0-300-01830-4
- Ermenc (ed), Joseph J (1989). Atomic Bomb Scientists: Memoirs, 1939-1945. Westport, CT & London: Meckler. ISBN 0-88736-267-2.CS1 maint: extra text: authors list (link) (1967 interviews with Heisenberg, Harteck and others).
- Gimbel, John U.S. Policy and German Scientists: The Early Cold War, Political Science Quarterly Volume 101, Number 3, 433–451 (1986)
- Gimbel, John Science, Technology, and Reparations: Exploitation and Plunder in Postwar Germany (Stanford, 1990)
- Goudsmit, Samuel with an introduction by R. V. Jones Alsos (Toamsh, 1986)
- Hahn, Otto My Life (Herder and Herder, New York 1970)
- Heisenberg, Werner Research in Germany on the Technical Applications of Atomic Energy, Nature Volume 160, Number 4059, 211–215 (16 August 1947). See also the annotated English translation: Document 115. Werner Heisenberg: Research in Germany on the Technical Application of Atomic Energy [16 August 1947] in Hentschel, Klaus (editor) and Ann M. Hentschel (editorial assistant and translator) Physics and National Socialism: An Anthology of Primary Sources (Birkhäuser, 1996) 361–379.
- Hentschel, Klaus (editor) and Ann M. Hentschel (editorial assistant and translator) Physics and National Socialism: An Anthology of Primary Sources (Birkhäuser, 1996) ISBN 0-8176-5312-0. [This book is a collection of 121 primary German documents relating to physics under National Socialism. The documents have been translated and annotated, and there is a lengthy introduction to put them into perspective.]
- Hoffmann, Klaus Otto Hahn – Achievement and Responsibility (Springer, New York etc. 2001) ISBN 0-387-95057-5
- Hoffmann, Dieter Between Autonomy and Accommodation: The German Physical Society during the Third Reich, Physics in Perspective 7(3) 293–329 (2005)
- Kant, Horst Werner Heisenberg and the German Uranium Project / Otto Hahn and the Declarations of Mainau and Göttingen, Preprint 203 (Max-Planck Institut für Wissenschaftsgeschichte, 2002)
- Landsman, N. P. Getting even with Heisenberg, Studies in History and Philosophy of Modern Physics Volume 33, 297–325 (2002)
- Macrakis, Kristie Surviving the Swastika: Scientific Research in Nazi Germany (Oxford, 1993)
- Mehra, Jagdish and Helmut Rechenberg The Historical Development of Quantum Theory. Volume 6. The Completion of Quantum Mechanics 1926–1941. Part 2. The Conceptual Completion and Extension of Quantum Mechanics 1932–1941. Epilogue: Aspects of the Further Development of Quantum Theory 1942–1999. (Springer, 2001) ISBN 978-0-387-95086-0
- Norman M. Naimark The Russians in Germany: A History of the Soviet Zone of Occupation, 1945–1949 (Belknap, 1995)
- Riehl, Nikolaus and Frederick Seitz Stalin's Captive: Nikolaus Riehl and the Soviet Race for the Bomb (American Chemical Society and the Chemical Heritage Foundations, 1996) ISBN 0-8412-3310-1.
- Oleynikov, Pavel V. German Scientists in the Soviet Atomic Project, The Nonproliferation Review Volume 7, Number 2, 1–30 (2000). The author has been a group leader at the Institute of Technical Physics of the Russian Federal Nuclear Center in Snezhinsk (Chelyabinsk-70).
- Walker, Mark German National Socialism and the Quest for Nuclear Power 1939–1949 (Cambridge, 1993) ISBN 0-521-43804-7
- Walker, Mark Eine Waffenschmiede? Kernwaffen- und Reaktorforschung am Kaiser-Wilhelm-Institut für Physik, Forschungsprogramm „Geschichte der Kaiser-Wilhelm-Gesellschaft im Nationalsozialismus" Ergebnisse 26 (2005)
- Walker, Mark. Nazi Science: Myth, Truth, and the German Atomic Bomb (Perseus Publishing, 1995). ISBN 0-306-44941-2
- Albrecht, Ulrich, Andreas Heinemann-Grüder, and Arend Wellmann Die Spezialisten: Deutsche Naturwissenschaftler und Techniker in der Sowjetunion nach 1945 (Dietz, 1992, 2001) ISBN 3-320-01788-8
- Bernstein, Jeremy and David Cassidy Bomb Apologetics: Farm Hall, August 1945, Physics Today Volume 48, Issue 8, Part I, 32–36 (1995)
- Beyerchen, Alan What We Know About Nazism and Science, Social Research Volume 59, Number 3, 615–641 (1992)
- Bethe, Hans A. (July 2000). "The German Uranium Project". Physics Today. 53 (7): 34–36. Bibcode:2000PhT....53g..34B. doi:10.1063/1.1292473.
- Cassidy, David C. Heisenberg, German Science, and the Third Reich, Social Research Volume 59, Number 3, 643–661 (1992)
- Cassidy, David C. Uncertainty: The Life and Science of Werner Heisenberg (Freeman, 1992)
- Cassidy, David C. A Historical Perspective on Copenhagen, Physics Today Volume 53, Issue 7, 28 (2000). See also Heisenberg's Message to Bohr: Who Knows, Physics Today Volume 54, Issue 4, 14ff (2001), individual letters by Klaus Gottstein, Harry J. Lipkin, Donald C. Sachs, and David C. Cassidy.
- Eckert, Michael Werner Heisenberg: controversial scientist physicsweb.org (2001)
- Ermenc (ed), Joseph J (1989). Atomic Bomb Scientists: Memoirs, 1939–1945. Westport, CT & London: Meckler. ISBN 0-88736-267-2.CS1 maint: extra text: authors list (link) (1967 interviews with Werner Heisenberg and Paul Harteck)
- Heisenberg, Werner Die theoretischen Grundlagen für die Energiegewinnung aus der Uranspaltung, Zeitschrift für die gesamte Naturwissenschaft, Volume 9, 201–212 (1943). See also the annotated English translation: Document 95. Werner Heisenberg. The Theoretical Basis for the Generation of Energy from Uranium Fission [26 February 1942] in Hentschel, Klaus (editor) and Ann M. Hentschel (editorial assistant and translator) Physics and National Socialism: An Anthology of Primary Sources (Birkhäuser, 1996) 294–301.
- Heisenberg, Werner, introduction by David Cassidy, translation by William Sweet A Lecture on Bomb Physics: February 1942, Physics Today Volume 48, Issue 8, Part I, 27–30 (1995)
- Hentschel, Klaus The Metal Aftermath: The Mentality of German Physicists 1945–1949 (Oxford, 2007)
- Hoffmann, Dieter Zwischen Autonomie und Anpassung: Die deutsche physikalische Gesellschaft im dritten Reich, Max-Planck-Institut für Wissenschafts Geschichte Preprint 192 (2001)
- Hoffmann, Dieter and Mark Walker The German Physical Society Under National Socialism, Physics Today 57(12) 52–58 (2004)
- Hoffmann, Dieter Between Autonomy and Accommodation: The German Physical Society during the Third Reich, Physics in Perspective 7(3) 293–329 (2005)
- Hoffmann, Dieter and Mark Walker Zwischen Autonomie und Anpassung, Physik Journal Volume 5, Number 3, 53–58 (2006)
- Hoffmann, Dieter and Mark Walker Peter Debye: "A Typical Scientist in an Untypical Time" Deutsche Physikalische Gesellschaft (2006)
- Hoffmann, Dieter and Mark Walker (editors) Physiker zwischen Autonomie und Anpassung (Wiley-VCH, 2007)
- Karlsch Rainer Hitlers Bombe. Die geheime Geschichte der deutschen Kernwaffenversuche. (Dva, 2005)
- Karlsch, Rainer and Heiko Petermann Für und wider "Hitlers Bombe" (Waxmann, 2007)
- Krieger, Wolfgang The Germans and the Nuclear Question German Historical Institute Washington, D.C., Occasional Paper No. 14 (1995)
- Pash, Boris T. The Alsos Mission (Award, 1969)
- Powers, Thomas Heisenberg's War: The Secret History of the German Bomb (Knopf, 1993)
- Renneberg, Monika and Mark Walker Science, Technology and National Socialism (Cambridge, 1994, first paperback edition 2002)
- Rhodes, Richard The Making of the Atomic Bomb (Simon and Schuster, 1986)
- Rose, Paul Lawrence, Heisenberg and the Nazi Atomic Bomb Project: A Study in German Culture (California, 1998). For a critical review of this book, please see: Landsman, N. P. Getting even with Heisenberg, Studies in History and Philosophy of Modern Physics Volume 33, 297–325 (2002).
- Schaaf, Michael Heisenberg, Hitler und die Bombe. Gespraeche mit Zeitzeugen. (GNT-Verlag, 2018)
- Schumann, Erich Wehrmacht und Forschung in Richard Donnevert (editor) Wehrmacht und Partei second expanded edition, (Barth, 1939) 133–151. See also the annotated English translation: Document 75. Erich Schumann: Armed Forces and Research  in Hentschel, Klaus (editor) and Ann M. Hentschel (editorial assistant and translator) Physics and National Socialism: An Anthology of Primary Sources (Birkhäuser, 1996) 207–220.
- Sime, Ruth Sime From Exceptional Prominence to Prominent Exception: Lise Meitner at the Kaiser Wilhelm Institute for Chemistry Ergebnisse 24 Forschungsprogramm Geschichte der Kaiser-Wilhelm-Gesellschaft im Nationalsozialismus (2005).
- Sime, Ruth Lewin The Politics of Memory: Otto Hahn and the Third Reich, Physics in Perspective Volume 8, Number 1, 3–51 (2006). Sime is retired from teaching chemistry at Sacramento City College.
- Walker, Mark National Socialism and German Physics, Journal of Contemporary Physics Volume 24, 63–89 (1989)
- Walker, Mark Heisenberg, Goudsmit and the German Atomic Bomb, Physics Today Volume 43, Issue 1, 52–60 (1990)
- Walker, Mark Nazi Science: Myth, Truth, and the German Atomic Bomb (Perseus, 1995)
- Walker, Mark German Work on Nuclear Weapons, Historia Scientiarum; International Journal for the History of Science Society of Japan, Volume 14, Number 3, 164–181 (2005)
- Walker, Mark Eine Waffenschmiede? Kernwaffen- und Reaktorforschung am Kaiser-Wilhelm-Institut für Physik, Forschungsprogramm „Geschichte der Kaiser-Wilhelm-Gesellschaft im Nationalsozialismus" Ergebnisse 26 (2005)
- Mark Walker Otto Hahn: Responsibility and Repression, Physics in Perspective Volume 8, Number 2, 116–163 (2006). Mark Walker is Professor of History at Union College in Schenectady, New York.
- (February 2002) Aaserud, Finn Release of documents relating to 1941 Bohr-Heisenberg meeting
- GlobalSecurity.org German Special Weapons
- Niels Bohr Archive Release of documents relating to 1941 Bohr-Heisenberg meeting (6 February 2002)
- (June 2008) Annotated bibliography on the German atomic bomb project from the Alsos Digital Library for Nuclear Issues
- Walker, Mark Nazis & the Bomb from Public Broadcasting Service Nova episode, Hitler's Sunken Secret (originally aired 8 November 2005).