In the summer of 1926, an army of Mexican Catholics launched a war against their government. Bearing aloft the banners of Christ the King and the Virgin of Guadalupe, they equipped themselves not only with guns, but also with scapulars, rosaries, prayers, and religious visions. These soldiers were called cristeros, and the war they fought, which would continue until the mid-1930s, is known as la Cristiada, or the Cristero war. The most intense fighting occurred in Mexico's west-central states, especially Jalisco, Guanajuato, and Michoacan. For this reason, scholars have generally...