Klaus Fuchs worked on the atomic bomb – and became a Soviet spy

35th anniversary of death
Role Model or Traitor? Klaus Fuchs worked on the atomic bomb – and became a Soviet spy

Klaus Fuchs fled the Nazis and became one of the leading physicists in Great Britain. In the “Manhattan Project” he helped develop the atomic bomb during World War II – but he passed on crucial information to the Soviet Union.

Klaus Fuchs already knew what was in store for him when his doorbell rang on February 3, 1950. The British nuclear physicist has long been suspected of spying for the Soviet Union. Now his camouflage has finally been blown, Fuchs finally confessed himself. He is arrested and put on trial. The judge described him as “Britain’s most dangerous man”. For Nobel Prize winner Hans Bethe, Fuchs was “the only physicist who changed the world”.

Both for good reason: Fuchs is considered one of the most brilliant physicists of his time and worked on the “Manhattan Project” – the notorious military research project that developed the atomic bomb. This gives him top secret information that could play a crucial role in the Cold War. Fuchs passed some of this information on to the Soviet Union – and ended up in prison for a long time.

Klaus Fuchs: A communist as a nuclear physicist

Klaus Fuchs was born in Germany in 1911 in Rüsselsheim am Main. He was politically involved in the communist party KPD, was persecuted after Hitler seized power and fled to Paris. He later moves on to the UK to continue and complete his physics and mathematics studies. His talent is shown by the fact that Fuchs is doing his doctorate twice: first he writes his doctoral thesis in mathematics, then in physics.

Fuchs became a British citizen in 1942. In his new homeland, in the middle of the Second World War, it had long been recognized that the scientist’s knowledge could also be used for military purposes. Fuchs becomes part of the British-Canadian nuclear program “Tube Alloys” in Birmingham. A little later he was promoted to the “Manhattan Project”. Scientists there, led by the physicist J. Robert Oppenheimer, are researching the use of nuclear fission for military purposes.

balance of power

But by then, Klaus Fuchs had serious doubts about his work and its possible implications for the world. Realizing the immeasurable damage an atomic bomb could do, he feared the weapon could fall into the hands of Nazi Germany, the regime he had fled. The convinced communist Fuchs also believes that the Soviet Union does not receive enough support from the British and Americans after the Wehrmacht attack. “The knowledge of nuclear research should not be the private property of one country, but should be shared with the rest of the world for the benefit of mankind,” he later explains. So Fuchs becomes a spy, codename “Rest”.

During his time at “Tube Alloys” he passed on information to the Soviets and shared his knowledge of research progress with the military intelligence service GRU. And they are considerable: Fuchs played a key role in the development of the “Fat Man” plutonium bomb and in testing the first atomic bomb. His information helps the Soviets under Stalin set up their own nuclear program. In 1945 the Americans used the atomic bomb for the first time in Hiroshima and Nagasaki at the end of the Second World War, in 1949 the Soviet Union detonated its first atomic bomb. From then on there is a balance of power.

Controversial Legacy

Fuchs, meanwhile back in the United Kingdom, was exposed in 1950, as we now know, by encrypted messages from the Soviet Union during the Second World War, which the British were only able to decrypt later. The physicist is arrested and put on trial. He was lucky enough to be tried in Great Britain, in the USA he might even have faced the death penalty. And: Officially, he only betrayed secrets to a friendly nation, because at this point in time the kingdom and the Soviet Union are still allies. Fuchs confesses: “It became clear to me that there are certain concepts of moral behavior that you cannot disregard,” he admitted in the process. He is sentenced to 14 years in prison.

Fuchs is serving nine years of this sentence before he is allowed to leave prison on probation and travel to the GDR. There, the spy convicted in the West is enthusiastically welcomed, gets a professorship at the Technical University in Dresden, a high position at the Central Institute for Nuclear Research, political influence and several awards.

On January 28, 1988 – 35 years ago – Klaus Fuchs died in East Berlin at the age of 76. His legacy remains controversial – traitor or role model? Fuchs followed his conscience, his defenders say, and recognized early on that a stalemate was needed on the nuclear issue. This “balance of terror” is considered one of the most important reasons why the Cold War that followed never escalated in the final instance.

Sources: MI5 / “Southgerman newspaper” / “World” / “Time”