Ruth Werner was the pen name of Ursula Ruth Kuczynski, born to a wealthy Jewish family in Berlin. She was drawn to the Communist movement as a teenager, and took part in some violent street demonstrations during the tumultuous years of the Weimar Republic. She married Rolf Hamburger, a left-wing architect with whom she had a son. In 1930, she and her husband moved to Shanghai, China, where Hamburger worked as an architect and Ruth began working for the foreign intelligence service of the Soviet military, known as the GRU. She wrote long articles for the Communist newspaper Rote Fahne (Red Flag) as Ruth Werner. She went to Moscow for formal training spy and was given the code name Sonja. In 1934, she was assigned to Manchuria, which had been invaded by Japan; the following year, she was assigned to Poland, where she had a daughter with a German-born comrade. In 1938, she was sent to Switzerland to set up a new spy ring. She met and married Len Beurton, a British Communist with whom she had another son, and went to the UK. There she met nuclear physicist Klaus Fuchs, who was working at Harwell, the top-secret British atomic research facility. She recruited him as an agent, and he provided copies of his own work and that of others. The information helped the USSR set up its own atomic bomb project in 1942. She also ran other agents, including her brother, Juergen, who was hired by the U.S. Army, and her father. Moscow broke off contact with her in 1946, without explanation. In 1950, after Fuchs confessed to espionage, she was warned to flee to East Berlin, where her husband and children joined her. She turned to writing, and published short stories, a biography, and her own autobiography, Sonja’s Report (1977). She was twice awarded the order of the Red Banner, the USSR’s highest military decoration.