This thesis is based on a mass of truly valuable prosopographical, literary, archival and other detail, some of it unpublished. As the author clearly indicates, problems arise from the ambiguities of the book's main concepts, since chivalry, crusade and even ‘crusader kingship’ virtually escape precise definition and they represent disparate categories which militate against easy comparisons or clear conclusions. While the ideals of chivalry and crusade had real meaning for certain classes of fourteenth-century Englishmen, the Jerusalem pilgrimage, holy warfare and the plunder and slaughter of Prussian pagans amid chivalric feasting had conflicting implications. Campaigning against enemies of the faith in hethenesse and invading Castile or Flanders for political motives could both be justified by crusading vows and papal indulgences. Monarchs might usefully emphasise their sacral role but Edward iii’s Order of the Garter had no overt crusading function even if it had a place in royal politics and warfare as well as in chivalric tournaments. The prototype of Chaucer's ‘verray, parfit gentil knyght’ might behave as a condottiere as well as a true crusader. Such contradictions provoked contemporary perplexities.

In covering so wide a field selection is unavoidable, so that to note omissions can be useful but need not imply criticism. Guard's extensive discussions do, however, contain some weaknesses. His grasp is somewhat less firm when dealing with complex foreign, and especially Aegean and Balkan, events and bibliographies. He omits detail on some political crusades on the debatable grounds that the facts are already well known. His impressive and useful list of English crusaders contains new names but he sometimes interprets licences to travel or fight as evidence for actual journeys. Guard (pp. 23–9) provides much interesting new data on English preparations for the Hospitaller passagium which was preached in 1308 and later sailed to Rhodes, though it is doubtful how many Englishmen eventually participated; his account of this expedition ignores much published literature on it and is not entirely satisfactory. The author (pp. 102–10) rightly emphasises the relatively unknown English presence, which included many mercenaries, in Amadeo of Savoy's Gallipoli crusade of 1366/7. He makes no mention of the greatest iconographical representation of the contemporary crusade in Andrea Bonaiuti's fresco of 1366/8 at Santa Maria Novella in Florence. Standing in front of the pope, the emperor, Peter of Cyprus, Amadeo of Savoy, Cardinal Albornoz and other major personalities is a striking lone and gartered figure, possibly Humphrey de Bohun, earl of Hereford. The gartered knight was perhaps inserted in the foreground to compensate for the absence of any English representative in the main line-up; that would have demonstrated foreign recognition of English crusading contributions.

The treatment of the military-religious orders is incomplete. Though its professed brethren could not technically be crusaders, the Hospital was the major permanent English institution devoted to the holy war and its members participated in crusades against the infidel. The English Order of St Thomas was insignificant. The Templars were dissolved in 1312 and their wide English possessions passed to the Hospital. Their trial had profound political and financial repercussions yet Guard never mentions the Temple. For a considerable period the most popular English participation was in the Teutonic Order's Prussian campaigns rather than with Hospitaller Rhodes; though it is unclear whether all such campaigners in Prussia were really crusaders, Guard lists them as such. As he himself admits (p. 5), Guard discusses the Hospital only partially. Its knight brethren, only about thirty in 1338, came from the gentry or knightly class and chivalry was not their business. Guard follows Simon Phillips's new book in emphasising the undoubted services that the English priors rendered to the crown as officials, captains and diplomats, but he gives much less attention to English contributions to Rhodes. Prior Robert Hales became royal treasurer and was murdered by the mob in the great revolt of 1381, yet Hales and the Turcopolier William Middleton served in the Alexandria crusade of 1365 and Middleton died in a campaign in Syria in 1367. The Turcoplier Richard de Overton apparently disappeared during the Hospitallers’ expedition to Epiros in 1378; Prior John Raddington seems to have died at Nikopolis in 1396; and the Turcopolier Peter Holt gave much service in the East. The English Hospital sent important funds to Rhodes amounting to more than one sixth of what the Western priories sent there between 1387 and 1415, and after 1407 the English nobility and others contributed generously to the Hospitaller castle at Bodrum on the Turkish mainland. The book does not mention that, despite England's adherence after 1378 to the Roman pope, successive English monarchs insisted on supporting the Hospitallers at Rhodes who recognised the Avignon papacy; they held that the defence of Christendom outweighed the rivalries of schismatic popes.

Guard's treatment of Geoffrey Chaucer's idealised Knight, with its immense bibliography, is strictly curtailed. Guard does not note that, with the curious exception of service to an infidel ruler against another infidel, the Knight fought uniquely against the infidel; nor that the Knight was apparently illustrating a Wycliffite position that holy war should be conducted without papal indulgences and was justified if directed against the infidel but not if against fellow Christians. The position of royal chamber knights such as the blood brothers John Clanvowe and William Neville demonstrated further ambiguities since they had strong Lollard sympathies. They were closely connected to Chaucer and both died in the Aegean in 1391.

These and other possible quibbles apart, Guard's book collects much useful information; he demonstrates the numerous contradictions in the real-life attitudes of certain classes to various concepts and institutions, emphasising the weight in personal choice contributed by family memory and tradition. Well after 1291 crusading enthusiasm remained alive among the English chivalric class in particular, and the crown could manipulate such sentiment in its own interests. The extent of the English contribution to the holy war overseas remains debatable. Omissions are unavoidable; this interesting book poses important questions, some distinctly controversial, for further research and reflection.