The Albigensian Crusades slash through the history of France and of the Church like a gaping wound. Bearing the name of the Albigenses heretics of the thirteenth century, the crusades are credited particularly for strengthening the French king's rule and making France the most powerful, wealthiest, and most populous state in Europe over the subsequent five centuries.

The wars waged for almost twenty years at the beginning of the thirteenth century. In addition to the power they afforded France, they brought inquisition and, Strayer contends, ultimately weakened the papacy and religion itself. This history of the crusades concisely and clearly sketches the conditions in what Strayer calls Occitania during the twelfth and thirteenth centuries, briefly details the origins and beliefs of Catharism, and contains a narrative account of the crusades and their consequences.