The agency's full name was the Main Administration of Corrective Labor Camps and Settlements (Glavnoye upravleniye ispravityelno-trudovykh lagerey i koloniy). It was administered first by the State Political Administration (GPU), later by the NKVD and in the final years by the Ministry of Internal Affairs (MVD). The Solovki prison camp, the first corrective labor camp constructed after the revolution, was established in 1918 and legalized by a decree "On the creation of the forced-labor camps" on April 15, 1919. The internment system grew rapidly, reaching a population of 100,000 in the 1920s. According to Nicolas Werth, author of The Black Book of Communism, the yearly mortality rate in the Soviet concentration camps strongly varied reaching 5% (1933) and 20% (1942–1943) while dropping considerably in the post-war years at about 1–3% per year at the beginning of the 1950s.
Aleksandr Solzhenitsyn, winner of the Nobel Prize in Literature, who survived eight years of Gulag incarceration, gave the term its international repute with the publication of The Gulag Archipelago in 1973. The author likened the scattered camps to "a chain of islands" and as an eyewitness he described the Gulag as a system where people were worked to death. Some scholars support this view, though this claim is controversial, given that the vast majority of people who entered the Gulag came out alive, with the exception of the war years. Although one writer, citing pre-1991 materials, claims that most prisoners in the gulag were killed, Natalya Reshetovskaya, the wife of Aleksandr Solzhenitsyn, said in her memoirs that The Gulag Archipelago was based on "campfire folklore" as opposed to objective facts. Similarly, historian Stephen G. Wheatcroft asserts that it is essentially a "literary and political work". Numerous other accounts from survivors state otherwise and the Mitrokhin Archive claimed that these memoirs were part of a KGB campaign, orchestrated by Yuri Andropov in 1974, to discredit Solzhenitsyn. However, this archive itself has its veracity in doubt; among other, more practical issues, by the same token with which Vasili Mitrokhin claimed the Soviet government would obviously be interested in discrediting Solzhenitsyn, Western governments would have as much interest in lending him credence.
In March 1940, there were 53 Gulag camp directorates (colloquially referred to as simply "camps") and 423 labor colonies in the Soviet Union. Today's major industrial cities of the Russian Arctic, such as Norilsk, Vorkuta and Magadan, were originally camps built by prisoners and run by ex prisoners.
Some suggest that 14 million people were imprisoned in the Gulag labor camps from 1929 to 1953 (the estimates for the period 1918–1929 are even more difficult to calculate). Other calculations by the historian Orlando Fidesa, refer to 25 million prisoners of the Gulag in 1928–1953. A further 6–7 million were deported and exiled to remote areas of the USSR, and 4–5 million passed through labor colonies, plus 3.5 million who were already in, or who had been sent to, labor settlements. According to some estimates, the total population of the camps varied from 510,307 in 1934 to 1,727,970 in 1953. According to other estimates, at the beginning of 1953 the total number of prisoners in prison camps was more than 2.4 million of which more than 465,000 were political prisoners. The institutional analysis of the Soviet concentration system is complicated by the formal distinction between GULAG and GUPVI. GUPVI was the Main Administration for Affairs of Prisoners of War and Internees (Russian: Главное управление по делам военнопленных и интернированных, GUPVI), a department of NKVD (later MVD) in charge of handling of foreign civilian internees and POWs in the Soviet Union during and in the aftermath of World War II (1939–1953). (for GUPVI, see Main Administration for Affairs of Prisoners of War and Internees). In many ways the GUPVI system was similar to GULAG. Its major function was the organization of foreign forced labor in the Soviet Union. The top management of GUPVI came from the GULAG system. The major noted distinction from GULAG was the absence of convicted criminals in the GUPVI camps. Otherwise the conditions in both camp systems were similar: hard labor, poor nutrition and living conditions, and high mortality rate.
For the Soviet political prisoners, like Solzhenitsyn, all foreign civilian detainees and foreign POWs (prisoners of war) were imprisoned in the GULAG; the surviving foreign civilians and POWs considered themselves prisoners in the GULAG. According with the estimates, in total, during the whole period of the existence of GUPVI there were over 500 POW camps (within the Soviet Union and abroad), which imprisoned over 4,000,000 POW.