U.S. code-breaking operation that revealed extensive Soviet spying in the United States during World War II and the early years of the Cold War. Beginning on 1 February 1943, the U.S. Army Signal Security Agency—commonly known as Arlington Hall and the predecessor organization to the National Security Agency (NSA)—began a secret program to decrypt and analyze thousands of encoded messages intercepted between Moscow and its diplomatic missions in the West. This program, which underwent at least a dozen code names, came to be known finally as Venona. In the course of decyphering the encoded diplomatic communications, the analysts uncovered evidence of espionage activities by the People's Commissariat of Internal Affairs (NKVD), the Soviet intelligence agency.

Gene Graebel, a former schoolteacher, began the project, and it took two years for Arlington Hall to break into the Soviet communications. Arlington Hall's Lieutenant Richard Halleck, a Signal Corps reserve officer who had been an archeologist at the University of Chicago, discovered weaknesses in the Soviet cryptographic system, namely that the Soviets were reusing some of the encoding in many of their messages. Halleck and his colleagues, many of whom were young women, went on to break into a significant quantity of Soviet trade traffic having to do with Lend-Lease and the Soviet Purchasing Commission. Cryptanalyst Meredith Gardner (a former language instructor at the University of Akron who spent twenty-seven years on the project) then employed these breakthroughs to decipher NKVD and Soviet Army General Staff Intelligence Directorate (GRU) communications, first breaking into these in December 1946. Arlington Hall worked in close collaboration with other U.S. agencies and the British MI5 intelligence agency, which joined the effort in 1948. Information provided by defecting Soviet cryptologist Igor Gouzenko also helped.

Among Venona's revelations were confirmation of the spying activities of Klaus Fuchs, David Greenglass, Bruno Pontecorvo, and Julius and Ethel Rosenberg. Venona also contributed to the unmasking of the Cambridge Five spy ring of British communist agents.

Soviet agents were able to inform the Komitet Gosudarstvennoi Bezopasnosti (KGB) of the Venona secret in 1948, after which Soviet communications became unreadable, but much valuable information was obtained. The Venona program continued until 1980. Beginning in July 1995, the NSA made six public releases of Venona translations and related documents. The first of these dealt with Soviet efforts to secure information on U.S. atomic bomb research. The remainder are a variety of NKVD communications, most of them during World War II.

Spencer C. Tucker

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Further Reading
Benson, Robert Louis, and Michael Warner. Venona: Soviet Espionage and the American Response, 1939–1957. Washington, DC: National Security Agency and Central Intelligence Agency, 1996.; Haynes, John Earl, and Harvey Kehr. Venona: Decoding Soviet Espionage in America. New Haven, CT: Yale University Press, 1999.; West, Nigel. Venona: The Greatest Secret of the Cold War. London: HarperCollins, 1999.