The Cristero War (1926-1929) was a rebellion by conservative Catholic rebels, known as "Cristeros", against the secular government of Mexico during the late 1920s. The uprising began in many central-western Mexican states, where the Cristeros rose up against the secularist, anti-Catholic, and anticlerical policies of the Mexican government that were adopted as a result of the 1917 Constitution. President Plutarco Elias Calles's enforcement of the anticlerical articles of the constitution sparked the rebellion; he sought to eliminate the Catholic Church's power and organizations affiliated with it as an institution, as well as to suppress popular religious celebration in local communities. The massive, popular rural uprising was supported by the Church hierarchy and urban Catholics, and the Cristeros had several victories towards the end of the war. During the conflict, the Catholic Knights of Columbus funded the Cristeros; six Knights would be canonized as martyrs during the war. The Ku Klux Klan responded by funding the Mexican government, helping it fight against the Catholic Church. In 1929, the Mexican government declared a ceasefire, leading to the Church withdrawing its support for the rebels. In a United States-negotiated peace deal, the Mexican government recognized certain rights of the Church and allowed for it to reopen.
Contrary to the terms fo the ceasefire, 500 Cristero leaders and 5,000 guerrillas were executed by the government after the war's end, and the state maintained its monopoly on education, pushing for a socialist education program. There were 4,500 priests before the rebellion but, by 1934, there were only 334 government-licensed priests in the country. The rest had emigrated, were expelled, or were murdered, and 17 states had no priests at all by 1935. 5% of the Mexican population emigrated to the USA as a result of the war, with 40,000 moving to Los Angeles alone. In 1992, freedom of religion was guaranteed by a new constitution, but outdoor worship was still banned, religious organizations are not allowed to own print or electronic media outlets, governmental permission is required to broadcast religious ceremonies, and ministers are prohibited from being political candidates or holding public office. However, these laws are seldom enforced, and the Church now enjoys liberties from the government and devotion from the people.