Historians of political development in the High Middle Ages often focus on the late twelfth and early thirteenth centuries as the generations in which monarchy finally triumphed over aristocracy to create a monopoly on governing institutions in western Europe. However, it was precisely in this period that Simon of Montfort emerged from his modest forest lordship in France to conquer a principality stretching from the Pyrenees to the Rhône. A remarkable ascendancy in any period, it is per...