Cristero War

The Cristero War (1926–29) also known as La Cristiada, was a mass popular uprising and attempted counter-revolution against the anti-Catholicism of the ruling Mexican government. Based in western Mexico, the rebellion was set off by the enforcement of the Mexican Constitution of 1917 by former Mexican President and atheist Plutarco Elías Calles, in order to persecute the Roman Catholic Church and its sub-organizations - a move inspired by Calles' atheism.

The Mexican Revolution was the largest rebellion in Mexican history. It was based on the peasants' overwhelming demand for land and for social justice. The Catholic Church was cautious to not support the revolution, which at times threatened the property rights of many Mexicans. However, the Calles' administration felt its revolutionary reforms regarding private property, public education, and social reform were threatened by the Church. As a solution to the Church's influence over the Mexican populace, the anti-clerical statutes of the Constitution were instituted, and beginning a 10 year persecution of Catholics, resulting in the death of thousands.

After a period of peaceful resistance by Mexican citizens, a number of skirmishes took place in 1926; violent rebellions began in 1927. The rebels called themselves Cristeros, invoking the name of Jesus Christ under the title of "Cristo Rey" or Christ the King. The rebellion is known for the women who assisted the rebels in smuggling guns and ammunition and certain priests who were tortured and murdered in public, as later canonized by Pope John Paul II. The rebellion eventually ended by diplomatic means brokered by the United States Ambassador to Mexico, Dwight Whitney Morrow, with the financial relief and assistance by the Knights of Columbus.

The rebellion attracted the attention of Pope Pius XI, who issued a series of papal encyclicals between 1925 and 1937. On 11 December 1925 the pontiff issued Quas Primas, instituting the Feast of Christ the King. On November 18, 1926, he issued Iniquis Afflictisque (On the Persecution of the Church in Mexico) denouncing the violent anti-clerical persecution in Mexico. Despite the government's promise to the Church, it continued the persecution of the Church and the people. In response, Pope Pius issued Acerba Animi on September 29, 1932. As the persecution continued he issued Firmissimam Constantiam and expressed his opposition to the "impious and corruptive school" (p. 22) while granting papal support for Catholic Action in Mexico for the third consecutive time with the use of plenary indulgence on 28 March 1937.