In A Most Holy War, historian Mark Pegg has produced a swift-moving, gripping narrative of this horrific crusade, drawing in part on thousands of testimonies collected by inquisitors in the years 1235 to 1245. He shows how a millennial fervor about "e;cleansing"e; the world of heresy, coupled with a fear that Christendom was being eaten away from within by heretics who looked no different than other Christians, made the battles, sieges, and massacres of the crusade almost apocalyptic in their cruel intensity. In responding to this fear with a holy genocidal war, Innocent III fundamentally changed how Western civilization dealt with individuals accused of corrupting society. This fundamental change, Pegg argues, led directly to the creation of the inquisition.