Persecution of Christians in the Soviet Union
Throughout the history of the Soviet Union (1922–1991), there were periods when Soviet authorities suppressed and persecuted various forms of Christianity to different extents depending on state interests. Soviet Marxist-Leninist policy consistently advocated the control, suppression, and ultimately, the elimination of religious beliefs, and it actively encouraged the propagation of Marxist-Leninist atheism in the Soviet Union.
Source: Wikipedia — Persecution of Christians in the Soviet Union (CC BY-SA 4.0)