Military counterintelligence of the Soviet Armed Forces was controlled by the nonmilitary Soviet secret police throughout the history of the USSR.^{[citation needed][clarification needed]}

The military counterintelligence departments of the Soviet Armed Forces existed at all larger military formations and were called Special Departments (Russian: Особый отдел (ОсО)) or third departments/sections. 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, important servicemen (e.g. commanding officers) against activities of foreign military attaché offices diplomats.