Russian Orthodox Church

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Stalinist era

The main target of the anti-religious campaign in the 1920s and 1930s was the Russian Orthodox Church, which had the largest number of faithful. Nearly all of its clergy, and many of its believers, were shot or sent to labor camps. Theological schools were closed, and church publications were prohibited.

The sixth sector of the OGPU, led by Eugene Tuchkov, began aggressively arresting and executing bishops, priests, and devout worshippers, such as Metropolitan Veniamin in Petrograd in 1922 for refusing to accede to the demand to hand in church valuables (including sacred relics). In the period between 1927 and 1940, the number of Orthodox Churches in the Russian Republic fell from 29,584 to less than 500. Between 1917 and 1935, 130,000 Orthodox priests were arrested. Of these, 95,000 were put to death, executed by firing squad.

http://en.wikipedia.org/wiki/Russian_Orthodox_Church

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