Led by the example of Bernard of Clairvaux, Cistercian monks turned their attention to the world outside the monastery walls in response to the threat posed by heretical Christians, in particular the Cathars. The white monks, with other intellectuals, turned to pen, pulpit and popular preaching to counteract heresy, some accepting posts as bishops and papal legates, helping and even directing the Albigensian crusade, and contributing to the formulation of procedures for inquisition. Kienzle examines this important but little-studied aspect of Cistercian history to discover how and why the Order undertook endeavours that drew the monks outside their monastic vocation. The analysis of texts about the preaching campaigns and their contexts illuminate the ways in which medieval monastic authors perceived heresy, preached, and wrote against it.