The Gulag was a system of Soviet labour camps and accompanying detention and transit camps and prisons. From the 1920s to the mid-1950s it housed political prisoners and criminals of the Soviet Union. At its height, the Gulag imprisoned millions of people. The word Gulag is an acronym of Glavnoye Upravleniye Ispravitelno-Trudovykh Lagerey (Russian: “Chief Administration of Corrective Labour Camps”).