A number of anti-clerical governments emerged in the 20th century. The 1926 Calles Law separating church and state in Mexico led to the Cristero War in which more than 3,000 priests were exiled or assassinated, churches desecrated, services mocked, nuns raped, and captured priests shot. Following the 1917 October Revolution, persecution of the church and Catholics in the Soviet Union continued into the 1930s, with the execution and exiling of clerics, monks and laymen, the confiscation of religious implements, and closure of churches. In the 1936–39 Spanish Civil War, the Catholic hierarchy allied with Franco's Nationalists against the Popular Front government, citing as justification Republican violence against the church. Pope Pius XI referred to these three countries as a "terrible triangle".