The Cristero War was a civil war which took place in Mexico between 1926 and 1929. The Catholic peasants and priests revolted against the Mexican government when former President Plutarco Elias Calles tried to enforce anti-Catholic and secular laws, some of which were against the religious tradition of the ordinary Mexican citizen. Among the anti-catholic measures, which served as the spark of the Cristero War, was the ban on wearing priest robes in open public places and the prohibition of religious rites, such as Mass and Holy Friday and saint processions, in public squares and streets.
At the beginning of 1927, the armed strife intensified when the leader of the Catholic Youth Association, Rene Capistran Garza, published a manifesto with the title: "The Hour of Victory Belongs to God". Armed only with bolt-action rifles, the catholic guerrilla fighters, called "Cristeros" ("followers of Christ"), obtained their first victory over the federal troops on February 23, 1927. However, the Cristero War would rage on for another two years, with savage battles between government forces and the Catholic guerrillas, with mass executions of Catholic peasants and priests carried out by federal troops. Finally, in 1929, after the assassination of elected-President Alvaro Obregon by a Catholic activist, the new President, Emilio Portes Gil, allowed the practice of religious rites again as he started a peace process, which put an end to the Cristero War.
Just as the intellectual revolutionary leaders of the French Revolution were strongly against the Catholic Church, the leaders of the Mexican Revolution were agnostic or atheist, approving a secular constitution in 1917. Thus, the Constitution of 1917 established a secular and scientific education for the first time in Mexico, separating the State from the Catholic Church. All the laws passed from then on were secular, free of religious influences. However, some leaders of the Mexican Revolution were not only Atheists but also felt a deep-seated aversion for the Catholic tradition and practices of the Mexican people. These leaders, like Obregon and Calles had initiated anti-religious campaigns in Mexico, passing measures, such as forbidding Catholic priests to perform Mass in public places.