In the 1920s and 1930s, the Catholic Church was subjected to unprecedented persecution in Mexico, as well as in Europe in Spain and the Soviet Union. Pope Pius XI called this the "terrible triangle". The "harsh persecution short of total annihilation of the clergy, monks, and nuns and other people associated with the Church", began in 1918 and continued well into the 1930s. The Civil War in Spain started in 1936, during which thousands of churches were destroyed, thirteen bishops and some 6,832 clergy and religious Spaniards were assassinated. After the widespread Church persecutions in Mexico, Spain and the Soviet Union, Pius XI defined communism as the main adversary of the Catholic Church in his encyclical "Divini Redemptoris" issued on 19 March 1937. He blamed Western powers and media for a "conspiracy of silence" with respect to the persecutions carried out by Communist, Socialist and Fascist forces. In Mexico, the Calles Law eventually led to the "worst guerilla war in Latin American History", the Cristero War. Between 1926 and 1934, over 3,000 priests were exiled or assassinated. In an effort to prove that "God would not defend the Church", Calles ordered Church desecrations in which services were mocked, nuns were raped, and captured priests were shot. Calles was eventually deposed. Despite the persecution, the Church in Mexico continued to grow. A 2000 census reported that 88 percent of Mexicans identify as Catholic. During the Spanish Civil War, Spanish republicans and anarchists targeted priests and nuns as symbols of conservatism, murdering large numbers of them. Confiscation of Church properties and restrictions on people's religious freedoms have generally accompanied secularist and Marxist-leaning governmental reforms. Worried by the persecution of Christians in the Soviet Union, Pius XI mandated Berlin nuncio Eugenio Pacelli to work secretly on diplomatic arrangements between the Vatican and the Soviet Union. Pacelli negotiated food shipments for Russia, and met with Soviet representatives including Foreign Minister Georgi Chicherin, who rejected any kind of religious education, or the ordination of priests and bishops, but offered agreements without the points vital to the Vatican. Despite Vatican pessimism and a lack of visible progress, Pacelli continued the secret negotiations. Pius XI ordered them to be discontinued in 1927, because they generated no results and he believed they would be dangerous to the Church's standing, if made public. The harsh persecution continued well into the 1930s. The Soviet government executed and exiled many clerics, monks and laymen, confiscating Church implements "for victims of famine", and closing many churches.