German nuclear program during World War II facts for kids
Quick facts for kids German nuclear program |
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The German experimental nuclear pile at Haigerloch (Haigerloch Research Reactor) being disassembled by American and British soldiers and others in April 1945
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| Founded | April 1939 |
| Country |  Germany |
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| Disbanded | 1945 |
During World War II, Nazi Germany worked on several research projects related to nuclear technology. These projects included nuclear weapons and nuclear reactors. They were known as the Uranverein (Uranium Club) or Uranprojekt (Uranium Project).
The first project began in April 1939. This was just a few months after nuclear fission was discovered in Berlin in December 1938. However, this first effort ended quickly. Many important German scientists were called to join the army (the Wehrmacht).
A second, larger project started on September 1, 1939. This was the same day Germany invaded Poland. This program was overseen by the army's Heereswaffenamt (Army Ordnance Office). It focused on three main areas: building a nuclear reactor (called Uranmaschine), producing uranium and heavy water, and separating uranium isotopes.
By January 1942, the German military decided that nuclear fission would not help them win the war quickly. So, the Army Ordnance Office handed the project over to the Reich Research Council. However, they continued to provide money for the research.
The program was spread across nine major research centers. Each center's director largely controlled their own research goals. Over time, fewer scientists worked on nuclear fission. Many moved to other projects that were more urgent for the war effort.
Important people in the Uranverein included Kurt Diebner, Abraham Esau, Walther Gerlach, and Erich Schumann. Schumann was a very powerful physicist in Germany. Diebner had more control over nuclear fission research than many other famous scientists.
Before the war, the Nazi government's policies forced many talented physicists, engineers, and mathematicians to leave Germany. Jewish scientists who stayed were removed from their jobs. Also, the German armed forces needed more soldiers. Many scientists were forced to join the military, even if they had important technical skills. These factors greatly reduced the number of skilled German physicists available for the project.
Historians agree that Germany's nuclear program never got close to making nuclear weapons. It stayed at the "laboratory level." Its main goal became to build a reactor that could keep a nuclear fission chain reaction going for some time. They also wanted to separate tiny amounts of uranium isotopes.
When the war in Europe ended in 1945, the Allied powers rushed to get their hands on Germany's nuclear technology. This included scientists, facilities, and materials. They also did this for other advanced German projects, like the V-2 rocket.
Contents
Discovery of Nuclear Fission
In December 1938, German chemist Otto Hahn and his assistant Fritz Strassmann made a huge discovery. They found that when they shot neutrons at uranium, it produced the element barium. This meant the uranium nucleus had "burst." Their findings were published in a science journal in January 1939.
Hahn shared his results with his colleague Lise Meitner, who had fled Germany. Meitner and her nephew Otto Robert Frisch confirmed Hahn's findings. They correctly called this process "nuclear fission." Frisch then proved this experimentally in January 1939.
Early Uranium Projects (1939)
In April 1939, a scientist named Wilhelm Hanle suggested using uranium fission in a "uranium machine" (a nuclear reactor). His colleague Georg Joos told the German Ministry of Education about the possible military and economic uses of nuclear energy.
Abraham Esau, a physicist, then organized a meeting for what became known as the first Uranverein (Uranium Club). This group included several physicists. They started informal work at the University of Göttingen. This early work stopped in the fall of 1939 when some scientists were drafted into the military.
At the same time, Paul Harteck and Wilhelm Groth from the University of Hamburg wrote to the Army Ordnance Office. They also mentioned the military uses of nuclear chain reactions. Separately, Nikolaus Riehl of the German company Auergesellschaft saw a business chance in producing uranium. His company had a lot of uranium waste from making radium. He contacted the Army Ordnance Office, which then ordered uranium oxide from Auer.
These three efforts were separate at first. But when World War II began, the Army Ordnance Office took over the nuclear research. This led to the second, more organized Uranverein.
The Second Uranium Project
In August 1939, the Army Ordnance Office (HWA) took control of nuclear research from the Reich Research Council. They ordered all nuclear experiments to stop. Physicist Kurt Diebner, an advisor to the HWA, started these actions.
Diebner organized a meeting in Berlin on September 16, 1939. Scientists like Walther Bothe, Siegfried Flügge, Otto Hahn, and Werner Heisenberg attended. The goal was to find out if generating nuclear energy was possible. They believed it could be a new energy source or have military importance. Even a "no" answer would be useful, as it would mean enemies couldn't use it either.
This group also called itself the Uranverein. The Kaiser-Wilhelm Institut für Physik (KWIP), a major research institute, was placed under army control. Diebner became its administrative director.
Heisenberg later said that in 1939, the scientists knew atomic bombs could be made. But he thought it would take "years," maybe "not before five." He said he didn't tell Adolf Hitler directly because he didn't want Hitler to order a huge effort to build the bomb. He and Albert Speer felt it was better to let the project be less urgent. Heisenberg said they presented the information in a way that protected them. If they promised a bomb and failed, there could be "extremely disagreeable consequences." They wanted to "make use of warfare for physics," not the other way around.
By January 1942, it was clear that a nuclear weapon wouldn't end the war soon. So, the army returned control of the KWIP to the Kaiser-Wilhelm Gesellschaft (Kaiser Wilhelm Society). In July 1942, the Army Ordnance Office passed control of the project to the Reich Research Council. The project was still considered important for the war. But it was split among different institutes. Each director set their own research plans.
The main research areas and leaders were:
- Walther Bothe: Measuring nuclear constants in Heidelberg.
- Klaus Clusius: Isotope separation and heavy water production in Munich.
- Kurt Diebner: Measuring nuclear constants at testing stations in Gottow and Stadtilm.
- Otto Hahn: Studying transuranic elements, fission products, and isotope separation in Berlin.
- Paul Harteck: Producing heavy water and isotopes in Hamburg.
- Werner Heisenberg: Working on the Uranmaschine (reactor), isotope separation, and nuclear constants in Leipzig and Berlin.
- Hans Kopfermann: Isotope separation in Göttingen.
- Nikolaus Riehl: Uranium production at Auergesellschaft.
- Georg Stetter: Studying transuranic elements and nuclear constants in Vienna.
At its peak in 1942, about 70 scientists worked on the project. Only about 40 of them spent more than half their time on nuclear fission. After this, the number dropped sharply. Many scientists moved to other urgent war-related work.
In June 1942, a meeting led by Albert Speer decided to continue the project only for energy production. Hitler then put the Reich Research Council under Hermann Göring's control. The goal was to make it more efficient. However, this change had little effect on the nuclear project.
Speer later said the atom bomb project was stopped in late 1942. Even if the science was there, it would have taken all of Germany's production resources. The bomb wouldn't have been ready before 1947. So, they focused on a "uranium motor" for the navy and a German cyclotron. By mid-1943, Speer even released 1200 tons of uranium for making ammunition.
Isotope Separation
Paul Peter Ewald suggested an electromagnetic isotope separator to produce enriched uranium (235U). Manfred von Ardenne, who ran a private research lab, took up this idea.
Von Ardenne's lab in Berlin-Lichterfelde was funded by his inventions and contracts. The Reich Postal Ministry, led by Wilhelm Ohnesorge, funded his nuclear physics research. He hired top scientists like Fritz Houtermans. Von Ardenne began building a prototype separator, but war shortages stopped the work.
Another small team at Henschel Aircraft Works also explored nuclear energy for airplanes. They wrote a detailed report in 1941. Their request to create a nuclear technology institute failed. But Hugo Watzlawek, a member of the team, wrote a textbook on nuclear physics. It described different ways to separate isotopes. He believed this research was the "new pathway" to becoming "Master of the World."
Heavy Water Production
Heavy water was important for reactors. Germany took over heavy water production facilities in Norway after invading in April 1940. However, the Allies and Norwegians sabotaged these facilities and destroyed heavy water supplies by 1943.
Scientists also considered using graphite (carbon) as a moderator. But Walther Bothe's calculations for carbon's neutron absorption were too high. This was likely due to boron impurities in the graphite.
Allied Efforts to Control German Nuclear Technology
Near the end of World War II, the Allied powers planned to seize German scientific discoveries. German nuclear fission technology was a top priority. They wanted to get these technologies, scientists, and materials first, to prevent rival allies from getting them.
The best-known US effort was Operation Paperclip. This operation aimed to capture German scientists and technology in many fields, including nuclear physics. Specific operations for German nuclear fission were Operation Alsos and Operation Epsilon. The Soviet Union also had its own similar operation.
American and British Efforts
Many German research facilities had moved out of Berlin due to air raids. The Kaiser-Wilhelm-Institut für Physik (KWIP) moved to Hechingen and Haigerloch in 1943 and 1944. These towns ended up in the French occupation zone. This move allowed the Americans to capture many German nuclear scientists.
Operation BIG
American Alsos teams carried out Operation BIG in 1945. They quickly moved through Germany, finding and collecting Uranverein materials. They captured a prototype reactor at Haigerloch and found records, heavy water, and uranium. All these were sent to the US for study in their own atomic program.
Operation Epsilon and Farm Hall
A main goal of Operation Alsos was to find, capture, and question German atomic scientists. Nine prominent German scientists from the Uranverein were captured and held in England as part of Operation Epsilon. These included Erich Bagge, Kurt Diebner, Walther Gerlach, Otto Hahn, Paul Harteck, Werner Heisenberg, Horst Korsching, Carl Friedrich von Weizsäcker, and Karl Wirtz. Max von Laue, who was not involved in the nuclear project, was also held.
The ten scientists were secretly held at Farm Hall, a manor house in Godmanchester. The house was secretly bugged, and their conversations were recorded and translated. It's unclear if the scientists knew they were being listened to.
Before the US announced the atomic bombing of Hiroshima, the German scientists were confident in their nuclear knowledge. Then, the British told them the BBC had announced the use of the atomic bomb. The Germans reacted differently. Hahn felt guilty for his discovery of nuclear fission. Many others, including Heisenberg, didn't believe it at first. Heisenberg argued it would take a "ton" of enriched uranium to make such a weapon. He made some errors in his calculations.
The recordings were made public in 1992. Experts concluded that Heisenberg had never done the critical mass calculation before. He himself said he "never believed one could get pure [uranium-]235." A week later, Heisenberg gave a more accurate lecture to his colleagues. Historians believe Heisenberg's errors show his work was mostly on reactors, not bombs.
At Farm Hall, the scientists discussed why Germany didn't build an atomic bomb. They developed a story, called the Lesart ("version"). This story claimed that German scientists chose not to build a bomb for Hitler. They said they either worked slowly, weren't enthusiastic enough, or even actively sabotaged the project. This story made them seem morally superior to Allied scientists, even though they worked for the Nazis.
Many historians of science do not believe the Lesart is true. As physicist Jeremy Bernstein explained, the Farm Hall reports show that the Germans knew general principles but hadn't seriously explored the details. They left many hard problems unsolved. They decided making a bomb in wartime Germany was impossible due to technical and economic reasons. Morality had nothing to do with it.
Oranienburg Plant
Nikolaus Riehl and Günter Wirths set up large-scale production of pure uranium oxide at the Auergesellschaft plant in Oranienburg. The Degussa company also helped with metal production.
The Oranienburg plant provided uranium for reactor experiments. For example, the G-1 experiment used 6,800 uranium oxide cubes (about 25 tons).
In November 1944, American Operation Alsos teams found out that the Oranienburg plant produced uranium and thorium metals. Since the plant would be in the future Soviet zone, General Leslie Groves, head of the Manhattan Project, recommended destroying it. This was to prevent the Soviets from getting the uranium equipment. On March 15, 1945, American bombers dropped many bombs on the plant, mostly destroying it. Riehl later said the Soviets knew the attack was aimed at them, not the Germans.
French Efforts
After the war, French forces occupied Hechingen, where much of the KWIP staff had moved. Fritz Bopp, a scientist at KWIP, described the French goals as taking over, forcing evacuation to France, and seizing documents and equipment. This was similar to American and Soviet actions, but on a smaller scale. To pressure Bopp, the French imprisoned him for five days.
Soviet Efforts
At the end of World War II, the Soviet Union sent special teams to Austria and Germany. Their goal was to find equipment, materials, and scientists for the Soviet atomic bomb project. These teams were led by Colonel General A. P. Zavenyagin. They included scientists from the Soviet bomb project.
Their top targets were the Kaiser-Wilhelm Institut für Physik (KWIP), the Frederick William University, and the Technische Hochschule in Charlottenburg.
German physicists who worked on the Uranverein and were sent to the Soviet Union included Robert Döpel, Nikolaus Riehl, and others. Günter Wirths, who worked for Riehl on uranium production, was also sent.
Manfred von Ardenne, who worked on isotope separation, was also sent to the Soviet Union. Other important German scientists like Gustav Hertz, Peter Adolf Thiessen, and Max Volmer also went. They had agreed that whoever first contacted the Soviets would speak for the rest. Thiessen, who had communist contacts, arrived at von Ardenne's institute with a Soviet Army major in April 1945.
Comparing to the Manhattan Project
The United States, British, and Canadian governments worked together on the Manhattan Project. This project successfully developed the uranium and plutonium atomic bombs. Its success came from four key things:
- A strong initial push from a small group of scientists.
- Full government support from a certain point.
- Almost unlimited people and industrial resources.
- Many brilliant scientists focused on the project.
Even with all these conditions, the Manhattan Project only succeeded after the war in Europe ended.
In Germany, there was distrust between the government and some scientists. By late 1941, German leaders knew their nuclear project wouldn't end the war quickly. So, the army gave up control of the project in July 1942.
For the Manhattan Project, its high priority allowed it to gather many skilled scientists. In Germany, however, many young scientists and technicians were forced into the military. Others had fled the country before the war due to anti-Jewish policies and political persecution.
Enrico Fermi, a leader in the Manhattan Project, was uniquely skilled in both theory and experiments. In Germany, the successes in Leipzig until 1942 came from the teamwork of theoretical physicist Werner Heisenberg and experimentalist Robert Döpel. They proved that neutrons could increase effectively in April 1942. Fermi's group achieved a similar neutron increase in a reactor-like setup in July of the same year.
In June 1942, Döpel's L-IV "Uran-Maschine" was destroyed by a chemical explosion. This ended their work in Leipzig. Despite more money being spent, the German groups could not get a reactor to become critical (start a self-sustaining chain reaction) before the war ended. Fermi's group achieved this in December 1942. This meant Germany lost its lead in nuclear research, even for energy production.
German historian Klaus Hentschel explained the differences in organization: The Uranverein was a loose, decentralized network of researchers with different goals. It was not like the Manhattan Project, which was a unified "big science" effort. In Germany, there was strong competition and rivalries among scientists for limited resources.
The Alsos investigation of the Manhattan Project concluded that Germany's nuclear development did not go beyond the laboratory stage. Their main focus was power production, not an explosive. Other scientific goals received more attention from the government.
The financial and human resources used by the two projects were very different. The Manhattan Project cost about US$2 billion (in 1945 money) and employed around 120,000 people at its peak. In total, about 500,000 people worked on it. In contrast, the Uranverein had a budget of only 8 million reichsmarks, which was about US$2 million (in 1945 money). This was a thousand times less than the American spending.
See also
- Germany and weapons of mass destruction
- Japanese nuclear weapons program
- Alsos Mission
- Operation Paperclip
Images for kids
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The Atomkeller (Atom Cellar) in Stadtilm, where some German nuclear experiments took place.
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Farm Hall, a manor house in Godmanchester, England, where German scientists were held.
