### Instruction:
What were gulags and who lived in them?

### Input:
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. 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 full official name of the agency changed several times.

The Gulag is recognized as a major instrument of political repression in the Soviet Union. 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. 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 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.

### Response:
Gulags were forced labour camps created during the Soviet Union that were used as an instrument of political repression and punishment. Gulags housed a wide range of individuals, from political prisoners to petty criminals.