Klaus Fuchs enrolled at the University of Leipzig in 1930, where his father was a professor of theology. Fuchs joined the student branch of the Social Democratic Party of Germany (SPD), as well as the the Reichsbanner Schwarz-Rot-Gold, the party’s paramilitary organisation. Since his father received a position at the Pedagogical Academy in Kiel, Klaus transferred to the University of Kiel, which his siblings also attended. He continued his studies in mathematics and physics there. In 1932, Fuchs offered to speak for Ernst Thälmann as the candidate for the presidential election wherefore he was expelled from the SPD and later joined KPD. In February 1933, Fuchs fled to England and became a research assistant at the University of Bristol.
Fuchs earned his Ph.D. in physics there in 1937. Later on, Fuchs switched to a research post at the University of Edinburgh working under Max Born, who was himself a German refugee. Together they published several papers and he also received a Doctorate in Science degree from Edinburgh. Fuchs applied to become a British citizen in August 1939, but his application had not been processed before the Second World War broke out in Europe in September 1939. There was a classification system for enemy aliens, but Born provided Fuchs with a reference that said that he had been a member of the SPD from 1930 to 1932, and an anti-Nazi. There, matters stood until June 1940, when the police arrived and took Fuchs into internment on the Isle of Man. In July, he was sent to an internment camp in Sherbrooke, Quebec, Canada, where he joined a communist discussion group led by Hans Kahle, a KPD member who had fought in the Spanish Civil War.
Max Born lobbied for his release. On Christmas Day 1940, Fuchs and Kahle were among the first group of internees to board a ship to return to Britain. Fuchs returned to Edinburgh in January, and resumed working for Born. On May 1941, he was approached by Rudolf Peierls of the University of Birmingham to work on the “Tube Alloys” program – the British atomic bomb research project. Despite wartime restrictions, he was granted British citizenship on 7 August 1942 and signed an Official Secrets Act declaration form.
Soon after, Fuchs contacted the secretary to the military attaché at the Soviet Union’s embassy, who worked for the GRU, the Red Army’s foreign military intelligence directorate. Fuchs (codename “Rest”) was then teamed up with a courier (“Sonia”) so he would not have to find excuses to travel to London. In 1943, Fuchs transferred to Columbia University, in New York City, to work on gaseous diffusion as a means of uranium enrichment for the Manhattan Project. From August 1944 Fuchs worked in the Theoretical Physics Division at the Los Alamos Laboratory, under Hans Bethe. Fuchs was one of the many Los Alamos scientists present at the Trinity test. Bethe considered Fuchs “one of the most valuable men in my division” and “one of the best theoretical physicists we had.”
Fuchs was highly regarded as a scientist by the British, who wanted him to return to the United Kingdom to work on Britain’s post-war nuclear weapons program. He returned in 1946 and became the head of the Theoretical Physics Division at the Atomic Energy Research Establishment at Harwell. From late 1947 to May 1949 he gave Alexander Feklisov, his Soviet case officer, the principal theoretical outline for creating a hydrogen bomb and the initial drafts for its development as the work progressed in England and America.
By September 1949, information from the Venona project indicated to GCHQ that Fuchs was a spy, but the British intelligence services were wary of indicating the source of their information. Under interrogation by MI5 officer William Skardon at an informal meeting in December 1949, Fuchs initially denied being a spy and was not detained. In January 1950, Fuchs arranged another interview with Skardon and voluntarily confessed that he was a spy.
It is very likely that Fuchs’s spying activities led the U.S. to cancel a 1950 Anglo-American plan to give Britain American-made atomic bombs. He was convicted on 1 March 1950 of four counts of breaking the Official Secrets Act by “…communicating information to a potential enemy.” After a trial lasting less than 90 minutes, Lord Goddard sentenced him to fourteen years’ imprisonment, the maximum for espionage, because the Soviet Union was classed as an ally at the time. In December 1950 he was stripped of his British citizenship. He was released after nine years and promptly emigrated to the German Democratic Republic. He continued his scientific career and achieved considerable prominence. He was elected to the Academy of Sciences and the SED central committee and was later appointed deputy director of the Institute for Nuclear Research in Rossendorf, where he served until he retired in 1979. He received the Patriotic Order of Merit, the Order of Karl Marx and the National Prize of East Germany.
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