Fuchs remained underground until he left Germany for Paris in July 1933-He was then twenty-one years old. “I was sent out by the Party, because they said that I must finish my studies because after the revolution in Germany people would be required with technical knowledge to take part in the building up of the Communist Germany.” To Harry Gold, who would meet him later in America, Fuchs's dedication would always be “noble”:
Here: While Klaus was a mere boy of 18 he was head of the student chapter of the Communist Party at the University of Kiel… and Klaus, a frail, thin boy, led these boys in deadly street combat against the Nazi storm troopers … and later, when the Nazis had put a price on his head, he barely managed to escape with his life to England… For a man of such convictions who fought this horror of Fascism at the risk of his life, I cannot help but express my admiration.
Student friends helped Fuchs find his way to England, where a Bristol family with Communist connections took him in. Theoretical physicist Nevill Mott, a professor at Bristol University, gave him an assistantship. Mott thought Fuchs “shy and reserved,” but saw another side at meetings of the Bristol branch of the Society for Cultural Relations with the Soviet Union, which sometimes staged dramatic readings of the texts of the purge trials then underway in Moscow. Fuchs chose to read the part of the prosecutor, shrill Andrei Vyshinsky, “accusing the defendants with a cold venom that I would never have suspected from so quiet and retiring a young man.”
After four years at Bristol, Fuchs moved in 1937 to Edinburgh to work with Max Born, one of the pioneers of quantum mechanics and himself an emigre. In Edinburgh, says Peierls, Fuchs “did some excellent work in the electron theory of metals and other aspects of the theory of solids.” Like Mott, Born also found the young German “a very nice, quiet fellow with sad eyes”; after Bristol Fuchs seems to have dissembled his political radicalism and swallowed his rage, although he did organize sending propaganda leaflets from Scotland to Germany.
He must have had trouble containing himself when he was interned as an enemy alien in May 1940 and sent to a camp on the Isle of Man. From there, jammed in with hundreds of other undesirables, he was deported by ship to internment in Canadian army camps that were short on latrines and running water. England was in a jingoist mood; by July, it had interned more than twenty-seven thousand Germans and Italians, many of them refugees from fascism, and would ship more than seven thousand abroad. Shattered by this second deportation, some of them committed suicide. A German U-boat torpedoed the
After inquiries and the intercession of friends, Fuchs was returned to England and released from internment on December 17, 1940, twelve days before his twenty-ninth birthday. He went back to Edinburgh and Max Born and his chosen work of physics, a thin, pale, stoop-shouldered young man of average height with prominent forehead and Adam's apple, myopic brown eyes watchful behind thick glasses, a habit of swallowing hard, frequently and audibly, a chain-smoker with stained fingers. Someone eventually wrote a clerihew about him:
Rudolf Peierls requisitioned Fuchs from Born sometime after the first of the year and took him in as a lodger; Peierls's wife Genia was exuberantly Russian and a great mother of young men, having previously taught Otto Frisch to shave daily and dry dishes faster than she could wash them. “[Fuchs] was a pleasant person to have around,” Peierls recalls. “He was courteous and even-tempered. He was rather silent, unless one asked him a question, when he would give a full and articulate answer; for this Genia called him ‘Penny-in-the-slot.’”
Since Fuchs was still an enemy alien, and was known to have been an active Communist in his homeland, clearance was delayed. The quiet young German started work on the atomic bomb at Birmingham in May 1941.
“When I learned the purpose of the work,” Fuchs testified later, “I decided to inform Russia and I established contact through another member of the Communist Party.” Fuchs went up to London in late 1941 and talked to Jurgen Kuczynski. “On his first contact with Kuczynski,” an FBI report paraphrases his testimony, “he informed him of his desire to furnish information to the Soviet Union.” Kuczynski put Fuchs in touch with a man he would come to know as “Alexander”: Simon Davidovitch Kremer, secretary to the military attache at the Soviet Embassy, who became his GRU control. In the next six months, Fuchs met with Alexander two or three times, once at the embassy, and gave him copies of the reports he was writing for Peierls. These included studies of isotope separation and calculations of critical mass as well as reviews of published German work in the field.
By early 1942, Lavrenti Beria's agents had bombarded him with so much information about British, French, German and American research toward an atomic bomb that he could no longer discount it. He ordered the British documents that the NKVD had received gathered together and a report prepared for Stalin. Copy No. 1 of that report, KZ-4, went to Stalin over Beria's signature in March 1942.
“Study of the question of military use of nuclear energy has begun in a number of capitalist countries,” Beria began cautiously. Work on the development of new explosives using uranium was being carried out in an atmosphere of “strict secrecy” in France, England, Germany and the US. Top secret documents obtained by the NKVD from its agents in England revealed that the British War Office was intensely interested in the problem of military use because of concern that Germany might solve the problem first.
Drawing directly on the MAUD report, Beria noted that “well-known English physicist G. P. Thomson” was coordinating the work in England and that U235 was the explosive isotope involved, extracted from ores of which there were large reserves in Canada, the Belgian Congo, Sudetenland and Portugal. In a significant garble, Beria reported that the French scientists Hans Halban and Lew Kowarski had developed a method for extracting U235 using uranium oxide and heavy water; in fact, Halban and Kowarski (using most of the world's supply of heavy water, fifty gallons spirited out of France just ahead of the Germans in tin cans by car and boat) had determined that a controlled chain reaction was possible using such materials without enrichment, information Yuli Khariton and Yakov Zeldovich would benefit in the course of time from learning.
Beria went on to discuss gaseous diffusion, noting that the British hoped to cooperate in development with the United States. Then he took up the bomb itself.
Peierls, Beria reported, had determined that ten kilograms of U235 would form a critical mass. “Less than this amount is stable and absolutely safe, but a mass of U235 greater than 10 kilograms develops in itself a fission chain reaction, leading to an explosion of tremendous force.” The British therefore proposed to design a bomb in which the “active part consists of two equal halves” and to drive them together at around six thousand feet per second. “Professor Taylor” — presumably Geoffrey Taylor, the English hy-drodynamicist — “has calculated that the destructive action of 10 kg of U235 would correspond to 1,600 tons of TNT.”
Imperial Chemicals had estimated that a plant to separate U235 “using Dr. Simon's system” would cost ?4.5 to ?.5 million, Beria went on. Then he offered a justification for bomb building that demonstrates how little anyone
