This work investigates the complex relationship between the crusading movement and the territorial, religious, and political expansion of Catholic Christendom from the eleventh to the early eighteenth century. John France, a noted scholar of medieval military history, utilizes a broad range of primary sources and historiographical analysis to argue that the crusades were not merely isolated religious conflicts but were central to the structural development of the Latin West. He examines how the ideology of holy war facilitated institutional growth and shaped the geopolitical boundaries of Europe and the Mediterranean world.

Historians frequently cite this text as a rigorous, high-level synthesis that successfully bridges the gap between military history and religious studies. Scholars appreciate the author's ability to maintain a neutral, analytical tone while navigating the dense and often contentious historiography of the crusades.