Some journalists and writers who question the reliability of such data heavily rely on memoir sources that come to higher estimations. The emergent consensus among scholars is that, of the 14 million prisoners who passed through the Gulag camps and the 4 million prisoners who passed through the Gulag colonies from 1930 to 1953, roughly 1.5 to 1.7 million prisoners perished there or they died soon after they were released. By the end of 1940, the population of the Gulag camps amounted to 1.5 million. The internment system grew rapidly, reaching a population of 100,000 in the 1920s. The Solovki prison camp, the first correctional labour camp which was constructed after the revolution, was opened in 1918 and legalized by a decree, 'On the creation of the forced-labor camps', on April 15, 1919. In 1918–1922, the agency was administered by the Cheka, followed by the GPU (1922–1923), the OGPU (1923–1934), later known as the NKVD (1934–1946), and the Ministry of Internal Affairs (MVD) in the final years. The camps housed a wide range of convicts, from petty criminals to political prisoners, a large number of whom were convicted by simplified procedures, such as NKVD troikas or other instruments of extrajudicial punishment. The Gulag is recognized as a major instrument of political repression in the Soviet Union. The full official name of the agency changed several times. English-language speakers also use the word gulag in reference to each of the forced-labor camps that existed in the Soviet Union, including the camps that existed in the post-Lenin era.

The Gulag was the government agency in charge of the Soviet network of forced labour camps which were set up by order of Vladimir Lenin, reaching its peak during Joseph Stalin's rule from the 1930s to the early 1950s. A punishment cell block in one of the subcamps of Vorkutlag, 1945

Baikal films summer camp