19 Meanwhile the sorry effects of this propaganda are before our eyes. Where Communism has been able to assert its power - and here We are thinking with special affection of the people of Russia and Mexico - it has striven by every possible means, as its champions openly boast, to destroy Christian civilization and the Christian religion by banishing every remembrance of them from the hearts of men, especially of the young. Bishops and priests were exiled, condemned to forced labor, shot and done to death in inhuman fashion; laymen suspected of defending their religion were vexed, persecuted, dragged off to trial and thrown into prison.
Source: Divini Redemptoris (Vatican.va)