"The communists seized power in October 1917 declaring a Soviet government. The new regime faced the hostility of conservative and bourgeois forces, including liberals, royalists and the Russian Orthodox Church. The Church had stated its opposition to the atheism and revolutionary nature of the Communists and threw its support behind the right-wing “White Army,” a coalition of anti-communist forces that declared war on the new state.
The victorious communists viewed the church as a subversive, counter-revolutionary organization, and closed many churches. According to the Library of Congress, after Stalin’s rise to power, persecution against Orthodox Christians escalated to a great extent. Many more churches were closed and many clergy were arrested and executed or sent to forced-labor camps known as gulags. 50,000 churches existed in pre-revolutionary Russia, but only 500 were still open by 1939."
That of course, deals only with Christians, a little further profound study into the fate of Jews, Muslims and Buddhists would reveal an exponential rise in in numbers these appalling figures.