Gulag
The Soviet forced-labor camp system through which roughly eighteen million people passed, built to punish, to terrify, and to supply unpaid workers.

Gulag is an acronym. It stands for the Main Administration of Camps, a bureaucratic department of the Soviet secret police, and it is a measure of the system that a filing-cabinet abbreviation became one of the twentieth century's words for hell.
The scale, from archives opened after 1991, is roughly this: some eighteen million people passed through the camps and colonies between 1930 and 1953, with the resident population peaking at around two and a half million in the early 1950s. Perhaps 1.6 million died in custody, with far more dying shortly after release or in the associated system of internal exile, which moved millions more without formal imprisonment. These are contested figures at the margins and beyond dispute in their order of magnitude.
What it was for
The camps had a genuine dual purpose, and that combination is what distinguishes them from Nazi extermination camps, which had one.
The first purpose was political. The camps absorbed the output of the terror: peasants who resisted collectivization, party members swept up in the purges of 1937 and 1938, entire deported nationalities, prisoners of war returning from German captivity who were treated as suspect for having survived, and enormous numbers of people convicted under Article 58 for counter-revolutionary activity on evidence that frequently did not exist.
The second was economic, and it is why the system grew so large. Stalin's industrialization required labor in places where free workers would not go: nickel at Norilsk above the Arctic Circle, gold at Kolyma in the Far East, timber, canals, and railways through frozen ground. Convict labor solved the recruitment problem. The White Sea Canal, dug largely with hand tools between 1931 and 1933 at a cost of tens of thousands of lives, was celebrated in a commissioned volume by leading Soviet writers as a triumph of reforging human material.
It was, as economics, terrible. Starving, coerced, and unskilled labor is unproductive, the camps needed a large guard apparatus, and the accounting was never honest. But it was available, and it did not have to be paid.
Life inside
Survival ran on a food scale tied to output. Prisoners who met their production quota ate; those who did not were fed less and could therefore work less, a mechanism that killed methodically without anyone giving an order. Criminal convicts were treated as socially close and often given authority over political prisoners, who were the lowest caste. Winter, distance, and the absence of anywhere to escape to did much of the rest.
The system began contracting almost immediately after Stalin died in March 1953, first through amnesties and strikes in the camps themselves, then decisively after Khrushchev's secret speech in 1956. Mass release and rehabilitation followed. The camp economy was found to be unprofitable and dismantled, though a smaller system of political imprisonment continued into the 1980s.
The echo
Two legacies matter.
The first is testimony. Aleksandr Solzhenitsyn's The Gulag Archipelago, published in the West in 1973 and built from his own years inside plus the accounts of more than two hundred other survivors, did more damage to the Soviet Union's standing among Western left intellectuals than any government campaign. It made the camps a documented moral fact rather than a Cold War allegation, and it is one of the very few books that measurably changed politics.
The second is unfinished. Russia never held anything comparable to the Nuremberg trials, no perpetrator of consequence was tried, and the reckoning was partial in the 1960s, reopened under perestroika, and then reversed. Memorial, the organization founded in 1989 to document the victims, was shut down by court order in 2021. Cities like Norilsk and Vorkuta still exist because the camps built them, and their populations still live on top of the reason.
A society that cannot look at what was done in its own name does not thereby stop being shaped by it.