Later , Koval was recruited by the Soviet Main Intelligence Directorate ( Главное Разведывательное Управление ) , or GRU . By the time he received his degree he had left Moscow under orders as part of a subterfuge . He was drafted into the Soviet army in 1939 to explain his sudden disappearance from the city . Though his parents had relinquished their US family passport , Koval returned to the US in 1940 , replacing a spy recalled during Stalin 's purges . His code name was DELMAR . Arriving in San Francisco , he traveled to New York City . According to Arnold Kramish , an American colleague he befriended and with whom he re-established contact in 2000 , it was there that Koval assumed deputy command of the local GRU cell . This outpost operated under the cover of the Raven Electric Company , a supplier to firms such as General Electric . Koval told coworkers he was a native New Yorker and an only child . He ingratiated himself with everyone he met . While Koval originally worked under a pseudonym , gathering information on toxins for use in chemical weapons , his handlers decided to have him work under his real name
Stalin 's purges
Great Purge
George Koval