A punishment cell block in one of the subcamps of Vorkutlag, 1945 The Gulag is recognized as a major instrument of political repression in the Soviet Union. The camps housed both ordinary criminals and political prisoners, a large number of whom were convicted in accordance with simplified procedures, such as NKVD troikas or other instruments of extrajudicial punishment. The agency was established in 1930 and initially was administered by the OGPU (1923–1934), later known as the NKVD (1934–1946) and the Ministry of Internal Affairs (MVD) in the final years. - en.wikipedia.org/wiki/Gulag