Pyotr Semyonovich Popov, a colonel in the Soviet military intelligence apparatus (GRU), was the first GRU officer to offer his services to the Central Intelligence Agency after World War II. Between 1953 and 1958, he provided the U.S. government with large amounts of information concerning military capabilities and espionage operations. Popov was dismissed from the GRU in November 1958, and placed on reserve status. In January 1959, after incriminating evidence was found in his apartment, he was run as a double agent for three months. He was then arrested in October 1959, and sentenced to death in January 1960.
(From: https://en.wikipedia.org/wiki/Pyotr_Semyonovich_Popov)
