The Albigensian Crusade, the first in which Christians were promised salvation for killing other Christians, lasted twenty bloody years - a long savage war for the soul of Christendom. In A Most Holy War, historian Mark Pegg has produced a swift-moving, gripping narrative of this horrific crusade. Pegg draws in part on thousands of testimonies collected by inquisitors in the years 1235 to 1245, accounts of ordinary men and women remembering what it was like to live through such brutal times. In responding to heresy with a holy genocidal war, Innocent III fundamentally changed how Western civilization dealt with individuals accused of corrupting society. This change, Pegg argues, led directly to the creation of the inquisition, the rise of an anti-Semitism, and even the holy violence of the Reconquista in Spain.