The pontificate of Honorius III (1216-27) ranks among the most important papal reigns of the thirteenth century: the pope organised two large-scale crusades to recover the Holy Land, the second of which recovered Jerusalem for the first since 1187; he presided over a 'golden summer' of papal-imperial relations with the medieval stupor mundi, Frederick II, emperor of the Romans and king of Sicily; he developed an original theological conception of his office; and he laid the foundations for a centralised papal financial machine. Yet, despite his significant impact on early thirteenth-century Christendom, Honorius has often languished in the shadow of his famous predecessor, Innocent III - a balance that the present book redresses. Grounded in extensive original research into the manuscripts of Honorius's letter registers, this study develops a revisionist interpretation of how the curia marshalled the crusading movement to recover the Holy Land. Questioning the utility of the historiographical construct of 'papal policy', this book provides new insights into crusade diplomacy, papal theology, the roles of legates, and the effectiveness of crusade taxation. It also includes a comprehensive and accessible introduction to the papal chancery and its documents, which will be of particular use to students and those approaching the medieval papacy for the first time.