Military counterintelligence within the Soviet Armed Forces was controlled by the nonmilitary Soviet secret police throughout the history of the USSR (1922 to 1991).[citation needed][clarification needed]
Military counterintelligence departments of the Soviet Armed Forces existed in all larger military formations, each called a Special Department (Russian: Особый отдел (ОсО)) or third department/section. The staff of the Special Department would usually establish a secret network of informants.
TGU (ТГУ КГБ СССР, 3 ГУ КГБ СССР ('third')) functionaries were responsible for protection of the military units and of important servicemen (e.g. commanding officers) against activities of foreign military attaché offices/diplomats.
Timeline[1]
Initially there was no common counterintelligence directorate. Various armies and fronts had their "Special Departments".