The Reformation foundations engaged with Augustinianism. Both Luther and Calvin thought along lines linked with the theological teachings of Augustine of Hippo. The Augustinianism of the Reformers struggled against Pelagianism, a heresy that they perceived in the Catholic Church of their day. In the course of this religious upheaval, the German Peasants' War of 1524–1525 swept through the Bavarian, Thuringian and Swabian principalities, leaving scores of Catholics slaughtered at the hands of Protestant bands, including the Black Company of Florian Geier, a knight from Giebelstadt who joined the peasants in the general outrage against the Catholic hierarchy.