The son of a German army officer, Gehlen joined his father’s regiment in 1918, and in 1936 was transferred to the General Staff where he played a key role in planning the Nazi invasion of the Soviet Union, Operation BARBAROSSA, which occurred in June 1941. The following year Gehlen was placed in charge of Foreign Armies East, the military intelligence organization collecting information on the Russian Front. He was dismissed in April 1945, and after the war, Gehlen offered his services, and what was left of his networks, to the U.S. forces. He began his collaboration with the United States in February 1946 and the relationship was formalized in 1949 following the creation of the Central Intelligence Agency.
In 1956 his organization was renamed the Bundesnachrichtendienst (BND) and he was its president until he retired in 1968, releasing his memoirs in 1971.
Gehlen proved a controversial figure, not least because his staff included several former Nazis and had been penetrated at a high level by the KGB. In October 1961 Hans Felfe was identified by a Polish defector, Michal Goleniewski, and was imprisoned for espionage. He had worked for the Sicherheitsdienst during the war and in November 1951 had joined Gehlen’s organization, having been recruited as a Soviet spy two months earlier.