Communism is a political ideology that seeks to establish a future without social class or formalized state structure, and with social organization based upon common ownership of the means of production. It can be classified as a branch of the broader socialist movement. Communism also refers to a variety of political movements which claim the establishment of such a social organization as their ultimate goal. Early forms of human social organization have been described as "primitive communism". However, communism as a political goal generally is a conjectured form of future social organization which has never been implemented. Marxism is a form of socioeconomic analysis that analyses class relations and societal conflict using dialectical materialism. There is a considerable variety of views among self-identified communists, including Bolshevism, Stalinism, Trotskyism, Maoism, council communism, Luxemburgism, Western Marxism and various currents of left communism, which are in addition to more widespread varieties. However, various offshoots of the Soviet and Maoist forms of Marxism–Leninism comprise a particular branch of communism that had been the primary driving force for communism in world politics during most of the 20th century.
The Soviet Union was a one-party federation, governed by the Communist Party with Moscow as its capital, which lasted from 1922 to 1991. The Soviet Union had its roots in the October Revolution of 1917, when the Bolsheviks, led by Vladimir Lenin, overthrew the Russian Provisional Government. There was a succession of Soviet secret police agencies over time: Cheka, GPU, OGPU, NKVD, NKGB, MGB and KGB. The activities of these agencies include: suppression of dissent and political opposition, persecution and deportation of deserters, religious people, Jews, invasions, fabrication of crimes, espionage and disinformation. Joseph Stalin's cult of personality became a prominent part of Soviet culture in December 1929, after a lavish celebration for Stalin's 50th birthday. The Soviet Union has been described as totalitarian police state. The Cold War was a state of geopolitical tension after World War II between powers in the Eastern Bloc and powers in the Western Bloc. Historians do not fully agree on the dates, but a common timeframe is the period between 1947 and 1991.
Mass killings occurred under some Communist regimes during the twentieth century: the Red Terror occurred during the Russian Civil War, Decossackization aimed at the elimination of the Cossacks, the Soviet famine of 1932–33 was a man-made famine that affected the major grain-producing areas of the Soviet Union, leading to millions of deaths, Dekulakization included the murder of peasants, purges of the Communist Party in the Union were a key ritual in which periodic reviews of members of the Communist Party were conducted to get rid of the "undesirables", NKVD prisoner massacres were a series of mass executions carried out by the Soviet NKVD secret police during World War II against political prisoners across Eastern Europe, the Soviet Union has also conducted several acts described as war crimes. Concentration camps came to be known as Gulags, established officially in 1930. Racism in the Soviet Union targeted Central, Eastern and South-Eastern Europeans, Jews and Asians. There was systematic political abuse of psychiatry in the Soviet Union, based on the interpretation of political opposition or dissent as a psychiatric problem. Homosexuality was criminalized from 1933 to 1993.