Gaik Badalovich Ovakimian
In 1940, leads developed by British and Canadian investigators in the Woolwich Arsenal spy case pointed the Bureau toward the senior KGB officer in America, Gaik Badalovich Ovakimian (covername GENNADI), whom the FBI arrested during a meeting on 5 May 1941 with an agent who had been turned by the FBI. The charge was Ovakimian violating the Foreign Agents Registration Act.  After the German invasion of the Soviet Union on 22 June 1941, he was traded back to Moscow for the release of several Americans and left the United States 23 July 1941. 
- Benson, Robert Louis, and Michael Warner, eds. Soviet Espionage and the American Response, 1939-1957. Washington, DC: National Security Agency/Central Intelligence Agency, 1996.
- John Earl Haynes and Harvey Klehr, Venona: Decoding Soviet Espionage in America, Yale University Press (1999).