The present volume is certainly a very important contribution, which will be useful to scholars, students and everyone interested in history. To my knowledge, it is the first collection of translated sources related to the anti-Ottoman crusade of 1456 which followed papal calls after the fall of Constantinople and ended up with the defeat of the Ottoman attempt to capture Belgrade: an army led by John Hunyadi, captain general of Hungary, and John of Capistrano, a Franciscan friar and the most prominent preacher of this crusade, lifted the siege of the city. This was probably the crucial and the most successful anti-Ottoman crusading campaign, which manifestly lacks modern source editions and source translations.

The book provides a good framework for those not yet familiar with the history of the crusade of 1456: an introduction with an overview of the main events of the Ottoman advance in the western direction, from its beginning to 1453, and an overview of the historiography of anti-Ottoman crusading. Then, at the end of the book, Mixson provides timelines both of the pre-history of the crusade of 1456, that is, of the Ottoman expansion to the West and some important contemporary events, and of the actual events of the crusade itself. Brief biographies of the main characters and maps at the end of the volume will also help any reader to get quickly into the essence of the expedition, its prelude and aftermath.

The book starts with a translation of the bull Etsi Ecclesia Christi, promulgated by Pope Nicholas v (1453), the first reaction of the Apostolic See to the fall of Constantinople. Then there was another important crusading bull, Ad summi pontificatus apicem, issued by Callixtus iii in 1455, which is not to be found in the volume, but this was merely a confirmation of the former papal call with some amendments. At the same time, the volume includes yet another very important bull, the De his superioribus annis (1456), a papal call for prayer for the cause of crusade issued soon after the siege of Belgrade was lifted, but when the pope was still unaware of this fact. There are also some important letters related to the preparation of the crusade. Much attention is paid to the correspondence of John of Capistrano, on whom much research has been done by Mixson over many years. Furthermore, many accounts of the battle at Belgrade, its prelude and aftermath, some of them composed by participants of these events, others by contemporaries, and still others present in much later chronography, are translated by Mixson. This includes the history of the victory of Belgrade by John of Tagliacozzo, a Franciscan who accompanied John of Capistrano, a c. seventy-page panegyric to Capistrano aimed at promoting his canonisation. Among other things, there is also an anonymous account of signs and wonders relating to the crusade. Finally, there are two texts concerning liturgical commemoration of the battle of Belgrade: from one of them we learn that Pope Callixtus iii established it in 1457 and tied it to the feast of the Transfiguration (August 6), and another is evidence that by 1500 the battle was actually commemorated. This is especially interesting as a parallel to the studies of the commemoration of the conquest of Jerusalem in 1099, to which some important articles of the last decade were devoted.

Sources translated by Mixson for this book are in Latin (mainly), German and Italian. There are relatively few texts not translated by Mixson himself, but reprinted by permission: such is the case of the introduction to Aeneas Silvius Piccolomini's famous speech Constantinopolitana Clades delivered at the Frankfurt diet in October 1454, as well as of several fragments of non-Western chronicles, and of the chronicle by John Thurocz published in the last chapter of the book. It is also worth mentioning that a couple of texts are still unpublished in their original versions: a text of the liturgy for taking the cross from Stiftsbibliothek, Salzburg, St. Peter, B. IX. 28, and a papal bull titled Omnipotentis Dei misericordia (1457) from the Vatican Secret Archive. As far as I can evaluate (not being a native speaker of English) translations are of a high quality. It is also worth mentioning that I have been able to check the translation of the above-mentioned unpublished text of the liturgy for taking the cross since I have a copy of this manuscript on which I am also working: I do not have a single critical remark to make on this translation. Just a minor remark: in the text of the bull Etsi Ecclesia Christi by Pope Nicholas v (1453) some passages are not included in the edition, and among them detailed prescriptions regarding various ways of obtaining the indulgence, which I think would be useful for many readers according to their research interests.

To conclude, I can only say that the book in question is a milestone in studies of the later crusades. The expedition to Belgrade is a remarkable event in the history of the fifteenth century, a result of a large-scale preaching campaign, possibly the strongest in the anti-Ottoman context, which in its turn followed so dramatic an event as the fall of Constantinople. In other words, this crusade and its historical framework, in my opinion still highly understudied, merits much more attention. The work done by Mixson in providing an extensive body of sources in translation is therefore very significant.