Under the doctrine of state atheism in the Soviet Union, there was a "government-sponsored program of forced conversion to atheism" conducted by Communists. This program included the overarching objective to establish not only a fundamentally materialistic conception of the universe, but to foster "direct and open criticism of the religious outlook" by means of establishing an "anti-religious trend" across the entire school. The Russian Orthodox Church, for centuries the strongest of all Orthodox Churches, was violently suppressed. Revolutionary leader Vladimir Lenin wrote that every religious idea and every idea of God "is unutterable vileness... of the most dangerous kind, 'contagion of the most abominable kind". Many priests were killed and imprisoned. Thousands of churches were closed, some turned into hospitals. In 1925 the government founded the League of Militant Atheists to intensify the persecution.