The Enemy Within: Crusading against Christians

Abstract Some of the most important crusades in the late Middle Ages were waged against men and women who had been baptized as Catholics. In some cases they comprised groups holding heterodox beliefs, against whom the normal procedures established by the Church for the investigation and suppression of heresy had failed, or could not even be applied. In others they were individuals in possession of secular authority, whose political opposition to the papacy was construed as posing a serious threat to the integrity and faith of the Church. Both forms of crusade, and especially the latter, aroused controversy in their day; and they still provoke lively disagreement amongst scholars of the crusading movement. In this chapter we shall therefore need not only to examine the crusades themselves, but also to give some attention to their historical origins and the polemic to which they gave rise.