The Great Purge was a period of systematic political repression and targeted elimination of suspect individuals that was carried out in the Soviet Union between 1934 and 1940. It took the form of warrantless arrests and lavish show trials at which the accused confessed to outrageous crimes.
The Soviet dictatorship began under Vladimir Lenin as a "temporary" measure, and was later inherited by Joseph Stalin. By the early 1930s, with peace and relative economic security, many in the Communist Party had begun to question the continuing need for such dictatorship. To cement his power, Stalin implemented a series of purges, beginning in 1934, that entailed the creation of a mythical army of "saboteurs" and "wreckers" who had infiltrated the party and had to be expelled, arrested and shot. The mechanisms of the Great Purge were extremely effective in breaking both the left-leaning faction of Trotsky supporters and the right-leaning supporters of Bukharin.
The terror began with the 1934 assassination of Sergei Kirov, a notable critic of Stalin's regime. Stalin was heavily implicated in the murder, but he used it as a pretext to initiate a round of arrests and show trials against his opponents. The pace of the repression accelerated for years until, by 1939, all of the admirals in the navy and half of the army's general officers had been imprisoned or shot, and whole nationalities, notably the Chechens, had been deported. By that time, the leader of the secret police, Yezhov, had himself been purged.