During the early 13th century the north of what is now France went to war with the south in a bloody crusade aimed at destroying the heretical sect known as the Cathars. The conflict was characterized by vicious guerrilla actions and the besieging of the innumerable fortified sites that dotted the landscape of the south. Illustrated with full colour artwork and stunning photographs, this book describes the castles and fortifications of the Cathar period, examining their design, construction and the role that they played during the Albigensian Crusade.