Klaus Fuchs: the scientist who became the Soviet super spy

There are often allegations made about how spies have changed the course of history. In the case of Klaus Fuchs, this is most certainly true: even by conservative estimates, it is claimed his information saved the Soviet Union two years in constructing their first atomic bomb.

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Fuchs was, in many respects, the typical scientist. Markus Wolf – head of East Germany’s secret police force, the Stasi – gave his first impression of Fuchs: “He was a cartoonist’s notion of the brilliant scientist, with a high forehead and rimless glasses out of which watchful eyes stared thoughtfully… these eyes came to life when Fuchs began to talk about theoretical physics. He had a boyish enthusiasm for the subject.”

From scientist to spy

Fuchs first arrived in the United Kingdom in 1933, fleeing his native Germany and certain Nazi prosecution. He was not a Jew – as many accounts have claimed – but was a communist with Quaker heritage. As an active member of the communist underground movement, his name became known to the Gestapo and he was, according to one of his biographers, “a wanted political criminal”.

His political allegiance was made known to British security authorities upon his arrival, yet no action was taken. He completed his doctorate at Bristol University and, in 1937, moved to Edinburgh University to undertake post-doctoral work, but the advent of war saw his career alter, radically. Following a short spell in Canadian internment, he returned to England and, with Britain’s increased need for competent scientists, the young German became a naturalised British citizen and was provided with security clearances so he could set to work on secret governmental work.

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The discovery in the late 1930s that the atom could be split through the process of nuclear fission was quickly followed by a realisation that this could have military implications. Fuchs was employed on something known as 'Tube Alloys', the British codename for the atomic bomb. His first work was to consider intelligence reports on the embryonic German atomic bomb programme, but quickly he became embroiled in research for Britain’s own nuclear weapon.

In August 1943, Prime Minister Winston Churchill and US President Franklin D Roosevelt signed an agreement in Quebec, cementing the Anglo-American atomic partnership. As a consequence, all developmental activity was moved to the US, which included the relocation of several British scientists to Los Alamos, New Mexico (the home of the Manhattan Project bomb programme led by Robert Oppenheimer). Among them was Fuchs.

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Schizophrenic state of mind

By this stage, the dichotomy of Fuchs’s persona was already taking shape – for while his reputation as a scientist expanded exponentially, his espionage role was also beginning to blossom. He had first provided information as early as 1941.

In his later confession to MI5, he described his schizophrenic state of mind: “I used my Marxist philosophy to establish in my mind two separate compartments. One compartment in which I allowed myself to make friendships, to have personal relations, to help people and to be in all personal ways the kind of man I had been before with my friends in or near the Communist Party. I could be free and easy and happy with other people without fear of disclosing myself because I knew that the other compartment would step in if I approached the danger point. I could forget the other compartment and still rely on it.”

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In December 1943, with his relocation to the US, Fuchs was given a new Soviet handler. To give an idea of just how prolific he had been in passing information to the Soviet Union, up until then he had provided more than 570 sheets of valuable material. In mid-1944, he moved to Los Alamos. Despite working in the theoretical division, Fuchs and the British Mission were far less compartmentalised than their American counterparts and, as a consequence, he was able to access a wide breadth and depth of information.

With the end of the war, Fuchs, at the insistence of the Los Alamos director, stayed on for an extra year. When he did return to England in 1946, he assumed the position of head of the theoretical physics division at the Atomic Energy Research Establishment, Harwell. While not working on bomb physics per se, Fuchs was a regular visitor and lecturer at Fort Halstead, the home of Britain’s nuclear weapons programme in the late 1940s.

There remained some question marks over his security, but whenever such points were raised it was repeatedly decreed that his usefulness outweighed any potential security risk

All the while, he continued to supply a steady stream of reports to the Russians, beginning with his first meeting in 1947 with Feklisov at the Nag's Head pub. Despite Fuchs’ exalted position, there had remained some question marks over his security, but whenever such points were raised it was repeatedly decreed that his usefulness outweighed any potential security risk.

During the latter stages of the war and the start of the Cold War, Anglo-American code-breakers had worked on cracking Soviet ciphers. This project, codenamed Venona, lasted for a number of years until the Soviets changed their cipher system in the late 1940s. Venona provided a wealth of information on the activities of numerous Soviet spies. The problem was that it only referred to them by their codenames, and a sizeable portion were not identified.

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The identity of 'Charles'

Amongst these was a spy known only as 'Charles'. Examination of what details were known about Charles led investigators to conclude that he could only be Fuchs – the facts fitted too precisely for it to be anyone else. The problem was that this information could not be revealed in court because the code-breaking effort was so secret. As such it was necessary to convince Fuchs to confess to his crimes.

In late 1949, Fuchs had gone to see the security officer at Harwell to discuss his father’s appointment to a university chair in East Germany. Henry Arnold, the security officer, had become friendly with Fuchs and they had spent many hours playing chess together. Fuchs was extremely concerned that his father’s appointment would mean he would have to leave Harwell and secret work.

By this time. Arnold knew of the incriminating evidence provided by Venona, confirming Fuchs to be a spy. He played on Fuchs’s insecurities about his father and invited William Skardon, an MI5 investigator, to speak to Fuchs about the situation, which he readily agreed to.

Fuchs talked of having two identities – scientist and spy – and all of a sudden the dividing line between the two was blurring beyond recognition

On 21 December 1949, Skardon met Fuchs for the first time. Sitting in his Harwell office, Fuchs described his background in Germany and his political views. While discussing his time in the US, Skardon suddenly asked whether Fuchs had been in touch with Soviet intelligence. Although Fuchs denied the allegation, he was thrown off balance. Throughout his espionage career he talked of having two identities – scientist and spy – and all of a sudden the dividing line between the two was blurring beyond recognition.

Fuchs and Skardon met again nine days later. Fuchs, who had just turned 38, continued to talk about his past. In a skilful move, Skardon managed to persuade him that whatever information he had passed had been a mistake, and that it would be far better for him to admit it so that he could resume his work. Fuchs was lost in thought over the New Year period but had, it would seem, made up his mind.

On 22 January 1950, he rang Arnold and said he would like to meet. Two days later, a meeting was arranged with Skardon and Fuchs confessed to being a Soviet spy.

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Fuchs had initially thought that he might deny everything and leave Harwell to start an academic career. Yet in his confession Fuchs stated why he had felt it necessary to come clean: “It then became clear to me that in leaving Harwell in those circumstances I would do two things. I would deal a grave blow to Harwell, to all the work which I had loved and, furthermore, that I would leave suspicions against people whom I loved, who were my friends and who I believed I was their friend. I had to face the fact that it had been possible for me in one half of my mind to be friendly with people, be close friends and at the same time to deceive them to endanger them.”

During the course of several conversations, Fuchs admitted his role in passing information to the Soviet Union, and in March 1950 was convicted at the Old Bailey to 14 years’ imprisonment.

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It was only the end of the Cold War and the opening of the Russian archives that we are now in a position to assess the role Fuchs’s espionage had on the Soviet programme, not to mention the nuclear arms race in general. Yuli Khariton, the Soviet chief nuclear weapons designer, has commented how “the design of the first Soviet atomic bomb was based on a rather detailed diagram and description of the first American bomb, which the Soviet Union obtained through the efforts of Klaus Fuchs and Soviet intelligence”.

Whilst Soviet scientists were developing their own indigenous atomic bomb, it was decided that in the first instance it made sense to copy the designs provided by Fuchs. It was known to work. This may sound rather simplistic now, but until the successful test of the world’s first atomic device in July 1945, no-one could be entirely sure that it would ever go bang.

Whilst Soviet scientists were developing their own indigenous atomic bomb, it was decided that in the first instance it made sense to copy the designs provided by Fuchs

Fuchs, although an excellent scientist, was politically rather naïve. His motives for providing information to the Soviets were not only that he believed, at least initially, in their Marxist cause, but that he did not want the US to have a monopoly over atomic weapons.

This latter belief may appear commendable 60 years later; it was not at that time. Yet by also aiding the British in much the same way as he had helped the Russians, Fuchs did ensure that the US monopoly did not last long. Fuchs’s biggest regret after his arrest was not over the enormity of his crimes, rather that the British government had decided to rescind his citizenship.

He returned to East Germany in 1959 a repentant man who, until the year before his death, refused to comment on what he had done.

Dr Michael Goodman is a professor of intelligence and international affairs and head of the department of war studies at King’s College London. He is also the author of Spying on the Nuclear Bear: Anglo-American Intelligence and the Soviet Bomb (Stanford University Press, 2008)

This article was first published in the February 2007 issue of BBC History Magazine