There can be little doubt that atheism was core to Communism. Although, Communism, as a socio-economic principle, does not forbid religion completely, it reflects the ideal of a classless society in all aspects of life including religion. Marx, Stalin and many others were professed atheists, believing in a social construct that would have promoted as an ideological objective the eradication of religion.
Targeting mainly the Russian Orthodox Church due to its large number of believers, the anti-religious campaign was initiated in the early 1920s. The Communist regime took possession of church property, propagated atheism and beleaguered believers, while almost the entire clergy were shot or sent to labor camps. Later, in the 1930s, theological schools were shut down and church publications were banned. By 1939, out of nearly 50,000 churches, only 500 were allowed to be open.
In 1941, after Nazis had attacked the Soviet Russia, Stalin decided to allow the worship of the Russian Orthodox Church, mainly as a way to strengthen patriotic support for the war against Hitler. By 1957 over 20,000 Russian Orthodox churches had become active again. Yet, in 1959, Khrushchev forced the closure of over 11,000 Russian Orthodox churches resulting by 1985 in almost 6,000 active churches. In majority, the church hierarchy was imprisoned or forced out, while KGB members took their places.
Until 1941, in the fear of a pan-Islamic movement, the Soviet Russia methodically and forcibly censored Islam. However, after the Nazi invasion, the Soviet government unofficially adopted a policy of permitting the religious belief and worship to Islam, while actively encouraging atheism among Muslims.
In fact, prohibitions against particular religions were determined by State interests, and also related to particular nationalities. The clergy of the Roman Catholic Church were forced out the Soviet Russia in the fear of the religious authority of the Pope. The Roman Catholic were shut down in majority and only two of the over 1,000 churches were allowed to operate. The Russian Orthodox Church forcibly absorbed the Autocephalous Orthodox Churches of Belarus in 1944 and the Ukrainian Catholic Church in 1946. Protestants were denominated, while attacks on Judaism were widespread throughout the Soviet period making the organized practice of Judaism almost impossible.
In 1944, the government established the All-Union Council of Evangelical Christian Baptists allowing them only the act of worship and prohibiting them from religious teaching and publications.
By and large, Communists regarded religious organizations as impairment towards the creation of a classless society. Viewing theism as slightly more liable for the killings of innocent people as atheism, Soviet regime wanted to convey the message that atheism cannot motivate anyone in any direction to do anything as it doesn’t encompass any belief at all. In that sense, people could lead a life free from superstitious and naïve beliefs related to God’s judgment.