AGRU officer, Major Popov volunteered in January 1953, while posted to Vienna, to supply the Central Intelligence Agency with information. As well as a wife and family in Moscow, Popov also had an Austrian mistress and became dependent on the CIA for financial support until his arrest in October 1959. He was tried in January 1960 and executed.
Popov was the first GRU officer to be recruited as an agent in the postwar era, and he supplied large quantities of information about his colleagues and their agents in the West. It proved impossible to communicate with him in Moscow, and he may have compromised himself when he reestablished contact with his American handlers through British channels upon his posting to East Germany.