During the Russian civil war, the enemies of socialism were indeed members of the Russian Orthodox Church. It was the church who opposed the revolution and who gave political support to the White Armies. This is understandably because the church was antisemitic and many Bolsheviks were of Jewish origin. This antisemitism was very strong in the Russian Orthodox Church. In Ukraine, many Jews were murdered by the White Armies and their Christian supporters. Nationalist Ukrainians hated the Russian Jews, because they thought that Marxism was a Jewish thing. In 1941, the Ukrainian antisemitic nationalists would aid the Nazi's in killing millions!
After the victory of the revolution, religion was limited. Church property was nationalized and many supporters of the church were prosecuted. Some were innocent and only jailed because they were people of faith. About 1200 priests were murdered between 1922 and 1926. This murdering of innocent religious people was wrong and a crime against humanity. But then again those people were the same ones who hated Jews and communists. So hatred was on both sides. Had the Whites won instead of the Reds, the reactionary forces would have killed many innocent Jews and communists!
In 1925, the Soviet government founded the League of Militant Atheists. The first militant atheist group to combat religion. But this combat was not through lethal force, the League of Militant Atheists was a debate club and not used to hunt down religious people. Instead the League wanted to debate with workers in the field and in the factories. Many of them were young communists who did not use brutal force. Religion did not become a target of the state until 1929!
It was Joseph Stalin who feared the remains of the Russian Orthodox Church. Stalin did not liked the idea that 80% of the Soviet people was still religious in 1929. So with his great terror, Stalin attacked the last churches in the USSR. By 1941 only 500 churches were still open, before world war 1 there were about 50.000 churches in all of Russia. But with the Nazi German invasion, Stalin needed religion again. The Russian Orthodox Church was used by the Stalinist government to fuel patriotism among the Red Army soldiers. Stalin allowed the priests to bless the soldiers of his army, while they went to fight the Germans.
The Soviet Union was never fully state-atheistic, because religion is always present in the Stalinist system. Joseph Stalin created his own cult of personality and replaced the Christian God by himself. He turned Lenin into a saint and all were forced to worship him as the ''great Lenin''. After the death of Stalin, the state became less and less hostile to religion. State-atheism in the USSR was not as strong as it was in Albania or China!
The People's Republic of China was a strict atheist nation between 1949 and 1978. In the era of Mao Zedong, religion became a symbol of old China. Buddhism, Christianity and Islam were seen by the Maoist government, as a danger to their power. Many Red Guard youth destroyed old temples and attacked religious people, they were fueled by hatred that Mao Zedong spread towards religion. Faith was seen as a remnant of China's feudalistic past and the Maoists wanted to destroy it all. In a way they were as bad as the religious rulers were before them. Only after Mao's death did the state ended its harsh anti-religion campaign. Today China is more tolerant of religion!
Only one Stalinist nation claimed to be total state atheistic. The Socialist People's Republic of Albania under Enver Hoxha, called itself completely free from religion. In order to keep the people atheistic, the Stalinist government closed all churches and mosques. Religion was banned in all forms. This was very radical even for a Stalinist nation. Many parents feared to tell their children about religion, because they could tell others. The constitution of Albania at that time said; The state recognizes no religion, and supports atheistic propaganda in order to implant a scientific materialistic world outlook in people" and the penal code of 1977 imposed prison sentences of three to ten years for "religious propaganda and the production, distribution, or storage of religious literature. A new decree that in effect targeted Albanians with Muslim and Christian names stipulated that citizens whose names did not conform to "the political, ideological, or moral standards of the state" were to change them!
The Republic of Cuba was a atheistic nation from 1961 till 1990. Today the Cuban government no longer claims to be atheist, they say that Cuba is a secular state. But over 200 priests were exiled after Fidel Castro took power. People who opposed Castro's revolution because of their faith were seen as ''counterrevolutionaries'' and jailed. In North Korea, the state was atheistic in its first years, but it soon degenerated into the Juche religion. Juche worship's Kim Il Sung and Kim Jong Il. North Koreans are forced to worship both death leaders as gods!
State atheism has died along with stalinism after 1991. We revolutionary socialists oppose state atheism, because it is wrong. A workers state cannot enforce atheism, it must not enforce a religion or try to oppose it. Religion or atheism are a personal matter and the state has no right to tell workers which religion is good or bad. Revolutionary socialists should support a full secular socialist state and a complete separation of state and church in all ways of life!