The All-Russian Extraordinary Commission (AREOC; Всероссийская чрезвычайная комиссия), abbreviated as VČK (ВЧК), and commonly known as Cheka (Чека; from the initialism ChK), was the first of a succession of Soviet secret-police organizations. Established on December 5 (Old Style) 1917 by the Sovnarkom, it came under the leadership of Felix Dzerzhinsky, a Polish aristocrat-turned-Bolshevik. By late 1918, hundreds of Cheka committees had sprung up in the Russian SFSR at all levels.
Ostensibly set up to protect the revolution from reactionary forces, i.e., "class enemies" such as the bourgeoisie and members of the clergy, it soon became the repression tool against all political opponents of the communist regime. At the direction of Vladimir Lenin, the Cheka performed mass arrests, imprisonments, torture, and executions without trial.
In 1921, the Troops for the Internal Defense of the Republic (a branch of the Cheka) numbered at least 200,000. They policed labor camps, ran the Gulag system, conducted requisitions of food, and put down rebellions and riots by workers and peasants and mutinies in the Red Army.
The organization was dissolved in 1922 and succeeded by the State Political Directorate or GPU.
The official designation was All-Russian Extraordinary (or Emergency) Commission for Combating Counter-Revolution and Sabotage under the Council of People's Commissars of the RSFSR (Всероссийская чрезвычайная комиссия по борьбе с контрреволюцией и саботажем при Совете народных комиссаров РСФСР, Vserossiyskaya chrezvychaynaya komissiya po borbe s kontrrevolyutsiyey i sabotazhem pri Sovete narodnykh komisarov RSFSR).
In 1918 its name was changed, becoming All-Russian Extraordinary Commission for Combating Counter-Revolution, Profiteering and Corruption.
A member of Cheka was called a chekist (чеки́ст). Also, the term chekist often referred to Soviet secret police throughout the Soviet period, despite official name changes over time.