Final answer:
Communists gained power in Russia through the Russian Revolution, the Bolshevik victory in the Civil War, and Joseph Stalin's consolidation of power.
Step-by-step explanation:
Communists gained power in Russia through a series of events that took place after the Russian Revolution in 1917. The Bolsheviks, led by Vladimir Lenin, emerged victorious in the civil war and established the Soviet Union in 1922. Joseph Stalin, who was initially the Party's general secretary, exploited his control over the Communist Party bureaucracy to consolidate power and become the leader of the Soviet Union. Stalin created a powerful police state, used propaganda extensively, and eliminated any opposition through terror and intimidation.