In the one-hundred years between 1810 and 1926 there were many civil wars in Mexico. The last of these wars. La Cristiada, was not fought, as were the previous civil wars, by groups seeking political control of Mexico. Rather, the genesis of this war was a question of who would control the Church in Mexico. The war began when President Plutarco Elias Calles attempted to enforce rigorously certain articles of the Constitution of 1917 as well as two laws which he promulgated. If Calles had succeeded, he would, in fact, have created a church in Mexico controlled by the federal government. The material to support this thesis was taken largely from the Mexican legal documents, the writing of Calles, other sources contemporary with the events described and some secondary sources. This thesis stresses the religious reasons for the La Cristiada and discusses the war itself not at all.