Christopher Tyerman's Debate on the crusades performs a valuable service and a nearly impossible task: introducing key historians of the crusade movement, explaining their arguments, and setting their work into proper historical context. It is an ambitious project. Crusade historiography began in 1099, as soon as the First Crusade ended. Medieval chroniclers, no less than their modern counterparts, worked with a theoretical agenda. As Tyerman astutely observes, they conceived of their narratives as expressions of theology. Further complicating Tyerman's project is the disagreement among professional historians on what the crusades actually were. The modern ‘pluralist’ school of thought defines crusading to include wars in Spain, the Baltic and even the New World. Tyerman's own God's war is perhaps the finest one-volume crusade history written from this perspective. In this book, however, Tyerman takes a more traditional approach, focusing on the Latin campaigns in the Levant and the resulting Middle Eastern settlements, which are surely complicated enough. After the first chapter, which introduces readers to the major medieval and renaissance writers, Tyerman organises his presentation around crucial topics in European history: the Reformation, the Enlightenment, nationalism, colonialism and the twentieth century. Several unexpected characters appear. The Enlightenment mathematician Leibniz weaves crusading history into a fantastical plan to invade Egypt. Francis Bacon, the inventor of the scientific method, defines crusading as a ‘rendez vous of cracked brains’, part of a wider historical project attacking the legitimacy of religious warfare. The Cold War double agent Guy Burgess studies at the feet of Sir Steven Runciman, the most famous (and in Tyerman's analysis, one of the least able) crusade historians who wrote in English. Of more direct scholarly appeal are Tyerman's descriptions of the true giants in crusade studies: Joseph Bongars, Henry iv's ambassador to German Protestant courts, whose collection of crusade sources helped to construct French national identity; François Michaud and Heinrich von Sybel, dominating figures of French and German scholarship, whose methods, though widely differing, set the agenda for European colonialism; Carl Erdmann, the ambivalent critic of German nationalism who ended his life in 1945 serving as a translator for Hitler's government; and Joshua Prawer, Benjamin Kedar and Ronnie Ellenblum, Israeli scholars of the crusader settlements, all working against the backdrop of Israeli-Palestinian conflict. The most notable historian whose contribution goes unmentioned is Tyerman himself. He coolly acknowledges the scholarly dominance today of Jonathan Riley-Smith and his students, closely associated with the ascendant pluralist doctrine, and puckishly hints that it can be dangerous to disagree with them (p. 233). In his own famous contribution to this dialogue on definitions, Tyerman asked whether we could speak of ‘crusades’ before the thirteenth century, in the absence of established theological doctrine, but in The debate on the crusades, he dismisses the entire historiographical moment as largely irrelevant. The absence of a first-hand analysis represents a lost opportunity in an otherwise engaging and extremely worthwhile book.