December 29, 1911 – Birth of Klaus Fuchs, Spy Who Passed Nuclear Secrets to the Russians

Klaus Fuchs was a German-born physicist who was convicted as a spy in Britain on March 1, 1950, for passing nuclear research secrets to Russia. He originally had fled to Britain from Nazi Germany, where he participated in the development of the bomb, and later, he went to Los Alamos, New Mexico to join the “Manhattan Project” directed towards developing nuclear power in the U.S.

Los Alamos I.D. Badge

Los Alamos I.D. Badge

The irony is that Fuchs was virtually ignored while he was at Los Alamos because the FBI was so focused on watching the bomb project’s director, Robert Oppenheimer. Oppenheimer was known to have had leftist leanings in his youth, but Fuchs had actually been a member of the (German) Communist Party, the only political group actively resisting Hitler. His family members had been imprisioned, killed, or driven insane by the Nazis.

Before arriving in the U.S., Fuchs had worked on a highly classified project in Britain and by 1942 was passing information to the Soviets about the British bomb program. No one knew, however, and he was brought, along with other talented British scientists, to Los Alamos. His behavior there gave no one cause for suspicion. He was quiet, worked hard, and loaned his car to physicist Richard Feynman to go home on weekends to see his dying wife. No one paid much attention to him.

Richard Feynman visiting his dying wife Arline at the Albuquerque sanatorium

By autumn of 1944, however, the Soviets were receiving the first of many intelligence reports directly from Los Alamos. Finally, in 1949, the FBI managed to decrypt Soviet cable traffic indicating that a Soviet spy had been operating out of Los Alamos and that the most likely suspect was Klaus Fuchs. He confessed early in 1950. In a statement he made then, he said:

At this time I had complete confidence in Russian policy and I believed that the Western Allies deliberately allowed Russia and Germany to fight each other to the death. I had, therefore, no hesitation in giving all the information I had …”

Nonetheless, much of the anger over this episode was directed toward Oppenheimer, since the spying had occurred “on his watch.”

As for Oppenheimer himself, he was stunned by the news, agreeing with his former secretary that “Fuchs had always seemed like such a quiet, lonely, even pathetic character as Los Alamos.” He also did not think Fuchs knew enough to do major damage. Oppenheimer’s days with security clearance were numbered, however. (An excellent account of what happened to Oppenheimer is provided in the book American Prometheus by Kai Bird and Martin J. Sherwin.)

J. Robert Oppenheimer

J. Robert Oppenheimer

Most scholars have agreed with Oppenheimer and with the assessment made by Hans Bethe in 1952, which concluded that by the time Fuchs left the thermonuclear program — the summer of 1946 — there was too little known about the mechanism of the hydrogen bomb for his information to be of any necessary use to the Soviet Union.

Meanwhile, the apprehension of Dr. Fuchs put investigators on a trail that led eventually to the conviction, at a trial in New York, of Ethel and Julius Rosenberg. They were electrocuted in 1953 at Sing Sing prison.

After Fuchs was convicted in Britain, he was imprisoned for nine years of a 14-year sentence, and released in 1959. He emigrated to Dresden, then part of East Germany. According to Thomas Reed and Danny Stillman, authors of a book on the atomic bomb, The Nuclear Express: A Political History of the Bomb and its Proliferation, Fuchs went on to share atomic secrets with China. Upon gaining his freedom, he apparently gave the mastermind of Mao’s weapons program a detailed tutorial on the Nagasaki bomb. A half-decade later, China detonated its first bomb.

Fuchs married a friend from his years as a student communist when he was released from prison. He continued his scientific career and achieved considerable prominence. He was elected to the German Academy of Sciences, and he received the Fatherland’s Order of Merit and the Order of Karl Marx. He retired in 1979 and died in 1988.

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