Gulag (from the Russian Glavonoye Upravleniye Lagerey, "main camp administration") was the branch of the Soviet secret police (the NKVD and later on the KGB) that dealt with concentration camps. Made famous by Alexander Solzhenitsyn's book The Gulag Archipelago, the Gulag system was the stage of perhaps the worst atrocities and crimes ever committed by a country towards its own citizens.
It was first established in the late 1920s, and some parts of it exist up until now. However, the Gulag is most widely associated with the late 1930s when, fed by the Stalinist repressions, it incarcerated more than 30 million people. Communist leadership continued to sponsor Gulag after Stalin's death, and a total of 40 million people have been killed by this system.
Gulag camps have all been positioned in the northern and north-eastern parts of Russia, mostly uninhabited regions with no roads or food. However, there are numerous deposits of valuable minerals in this region, and the inmates were forced to mine them in inhuman conditions: in spite of very cold climate, the inmates have never been adequately clothed, fed or healed if ill, nor were they given any means to combat the lack of vitamins that led to scurvy. In some camps, fatality rate during the first months was as high as 80%.
The Gulag system grew to became a very deep and sad aspect of the Russian culture. Many songs by people such as Vladimir Visotsky and Alexander Gorodnitsky (neither of whom ever served time in the Gulag camps), that deal with life in camps, became a part of the Russian folklore, thus emphasizing the extent to which the Gulag affected every Russian's life.