Fitin became deputy chief of the NKVD's foreign intelligence in 1938, then a year later at the age of thirty-one became chief. The Russian Foreign Intelligence Service credits Fitin with rebuilding the depleted foreign intelligence department after Stalin's Great Terror. Fitin also is credited with providing ample warning of the German Invasion of 22 June 1941 that began the Great Patriotic War. Only the actual invasion saved Fitin from execution for providing the head of the NKVD, Lavrenty Beria, with information General Secretary of the CPSU, Joseph Stalin did not want to believe. Beria retained Fitin as chief of foreign intelligence until the war ended but demoted him.