"In a country 96% Catholic, how can one speak of a religious war?" The purpose of this thesis is to prove that the Cristero Rebellion, fought in Mexico between the years 1926 and 1929, was exactly that - a religious war. Using primary and secondary sources, I will make clear how anti-Catholicism and anti-clericalism was used by the political and military elite in the Revolutionary government to attempt to remove, once and for all, the power and influence of the Catholic Church in Mexico, despite the religious devotion of those who supported it. I will also examine how religiosity, and the concept of martyrdom, was ingrained in the Cristeros and their supporters, and how these notions affected their decisions to fight and die for Cristo Rey.