For many nonspecialists, and even some specialists, the idea of an intellectual history of medieval warfare appears to be an oxymoron. Building upon the conceit of the exceptionally influential work of Hans Delbrück,[1] many scholars assume that military science died with the Roman empire, only to reemerge in renaissance Italy, or even as late as the early modern period. All too often, medieval commanders are depicted in both popular and scholarly works[2] as acting on gut instinct, since they lacked any specialized training. Such a view, however, is utterly at odds with the reality of medieval warfare, which was dominated by sieges requiring of military commanders a range of technological, tactical, and logistical capabilities. Furthermore, voluminous contemporary evidence attests to the efforts of medieval governments to educate future commanders for their duties.[3] Military education in the medieval period, as in ancient Rome, stressed learning from historical works and military handbooks, as well as from practical experience in the field in order that leaders might acquire the myriad prerequisites for commanding armies, whether in siege, in battle, or on the march.

In his study of the English cleric John of Salisbury (c. 1120–c. 1180; hereafter, "John"), historian John Hosler (Morgan State Univ.)[4] shows how medieval texts shaped the process of military education, and how modern scholars may use them to better understand the conduct of war, in this case, during the mid-twelfth century. John left a copious literary legacy, including three major books, Policraticus, Metalogicon, and Historia Pontificalis, two hagiographies (of Anselm and Thomas Becket), two long poems, and 325 letters, including correspondence with political figures of his day, among them many bishops, Thomas Becket as both chancellor of England and archbishop of Canterbury, and with the papal curia.

Hosler demonstrates that John was convinced that political leaders should study warfare in order to defend the interests of their people and the state (res publica). John diligently offered practical advice about military matters to his correspondents and the dedicatees of his major works. His longest sustained treatment of war is in book 6 of his Policraticus, but military themes permeate all his writings.

Despite John's interest in the military sphere and commitment to educating appropriate audiences about it, Hosler appreciates the methodological pitfalls of examining a body of work composed over two decades; for example, is it appropriate to combine information from texts at different stages of John's life and career in order to support claims about his didactic intentions? And what of John's own sources, which are crucial to assessing the validity of the English cleric's observations about contemporary warfare. Hosler addresses both issues with sensitivity; he provides enough context to indicate whether John's teachings are consistent over time and the extent to which his sources of information are sufficiently reliable to inspire a modern reader's confidence in his depiction of contemporary events.

Following a brief introduction discussing John's place in the historiography of twelfth-century military affairs and stating his book's argument, Hosler organizes his text in six thematic chapters. The first chapter, "John's Military Lexicon," treats the semantic nuances of key terms in John's writings, notably the (Latin) word miles (genitive militis). Chapter 2, "The Soldiers," concerns John's treatment of the recruitment, training, and discipline of soldiers. Chapter 3, "Organization and Logistics," considers his thoughts on the assembling, equipping, and moving of armies. In chapter 4, "Armies at War," Hosler examines his presentation of strategy and tactics, and the requirements of good leadership. The fifth chapter, "The Language of War," has a rather different focus—John's use of military language in writing of nonmilitary matters, including, for instance, the struggle of individuals to live virtuous lives and of the church to free itself of secular control. Chapter 6, "Contemporary Military Accounts," evaluates in detail John's texts as evidence for contemporary military actions, particularly where he is the main or sole source for an event.

The volume is equipped with extensive footnotes and two appendices. Appendix A lists the sources of John's quotations and allusions. Appendix B tabulates every instance of scores of specific words, such as miles, equites, auxiliares, signifer, and gladius, in all their forms in the corpus of John's work, together with indications of how they have been rendered in modern English translations. Rounding out the text is a bibliography of primary sources and secondary literature, as well as a useful index.

Hosler succeeds in proving that John intended to provide instruction in military affairs to men who could make practical use of it in the conduct of war. He shows that he was no cell-bound cleric ignorant of affairs in the wider, secular world. He had traveled extensively throughout western Europe and, even if he did not personally experience battle, he certainly observed the broader conduct of war, including troop mobilizations and the movement of armies. Hosler argues that John's habit of sharing the wisdom of Roman military authors, particularly Vegetius and Frontinus, suggests that his contemporaries valued the work of these Roman authorities (auctores) not as mere antiquarian novelties, but treasuries of useful information and ideas. Indeed, Vegetius's Epitoma rei militaris was the most copied secular text of late antiquity and the Middle Ages.

Hosler's analysis of John's specialized vocabulary is an especially welcome aspect of his book, indispensable to correctly construing medieval texts as sources for military matters of the era. Unfortunately, in discussing one key word, miles, Hosler makes a serious methodological error. He begins by correctly insisting that the willy-nilly traditional translation of the word as "knight" is inappropriate and discussing important scholarly considerations of the word (13–14).[5] For Hosler, the typical treatment of the term "knight" fails to convey the wide semantic field of John's use of miles, which encompasses "instances in which he is explicitly describing a 'knight' (reflective of the Prestwich and Gillingham definitions of 'mounted warrior'); vague references to nondescript warriors; and those in which he is describing a different type of soldier entirely" (14).

Problematic in Hosler's approach is his assumption that John meant three different things by miles. John likely knew that some of the men he describes as milites were of high social standing. But his choice of the same term to denote lower-class soldiers points to similarities rather than the differences between the two—that is, their common status as fighting men.

To verify that a given author chose miles to denote "knight," a man of higher social and legal status than other laymen, one would have to show that he used miles in civilian contexts, for example, of juries or assizes, and not to designate men of inferior status to that of "knights." Such a distinction is quite clear in sources for medieval England in the second half of the thirteenth century, when only men of elevated status could be called milites while on military campaign. At the same time, men equipped like milites with warhorses and armor but of lower social status were not so designated and received less pay in the king's service.

This semantic inaccuracy, though serious, is an exception and does not detract from what is otherwise a very successful book. Hosler deserves great credit for so cogently demonstrating the importance of John of Salisbury as military thinker and reliable source regarding contemporary ideas about the conduct of war and our own understanding of them. One hopes his book will be a model for future studies of other medieval writers that will further illuminate the significance of military education in the medieval period. I recommend this text both to specialists and to medieval scholars generally. Individual sections of the book will also be suitable for graduate courses in medieval history.