This dissertation investigates the growth and decline of a major Mediterranean commercial economy at the crossroads of Christian Europe and the Muslim Middle East from 1100 to 1400. New and old evidence uncovers the transformation of the commercial economy of the Byzantine Empire in its relations with the Middle East, western Europe, and Crusader principalities established in Byzantium's ruins. Ultimately, this work helps identify and understand the economic roots for enduring divisions between East and West, and it is unique in observing from Byzantium's perspective the transformation of the Middle East--the economic dynamo of the ancient and medieval Mediterranean. / History

Ce mémoire porte sur le traité de Venise de 1201, passé entre les barons de la Quatrième Croisade et la république de Venise, pour l’affrètement d’une flotte incluant transport et vivres. L’étude du Traité est d’autant plus importante que, les croisés manquant à leurs obligations, cet accord eut un impact déterminant sur la suite de la Croisade, se plaçant ainsi au cœur de sa déviation vers Constantinople. Le mémoire analyse d’abord la nature et l’ampleur des engagements pris par Venise, en essayant de quantifier et de mesurer en termes économiques le nombre de bateaux et de croisés transportés, ainsi que le poids et le coût des provisions pour hommes et chevaux. Cette analyse, basée sur la comparaison avec des contrats analogues, prouve que la somme de 85 000 marcs d’argent convenue avec les barons n’était en rien exagérée. Parallèlement, le mémoire évalue ce que pouvait signifier, dans le contexte économique de l’époque, une telle somme, et tente d’identifier les raisons pour lesquelles les croisés furent dans l’impossibilité d’honorer leur part du contrat. Cette analyse montre que, contrairement à une certaine historiographie traditionnelle, il serait faux d’imputer aux Vénitiens la responsabilité du détournement de la Croisade ou de les taxer d’intransigeance, de cupidité, voire de duplicité. L’effort fourni par la République indique qu’elle mit tout en œuvre pour que l’entreprise fût une réussite. L’interruption du commerce, la construction de nombreux navires, la réquisition de milliers de marins pour manœuvrer la flotte et la logistique pour approvisionner des dizaines de milliers d’hommes témoignent toutes de l’ampleur de l’implication vénitienne. C’est le défaut de paiement des croisés, qui força le doge Henri Dandolo à se commettre plus avant encore, joignant irrémédiablement la fortune de la ville marchande à celle de l’expédition. / This master’s thesis is about the Treaty of Venice, made in 1201 between the Fourth Crusade’s barons and the Republic of Venice, regarding the transportation and provisioning of a fleet bound for the Levant. The importance of this study stems from the Crusaders’ default on their obligation, which had a decisive impact on the course of events, thus placing it at the heart of the Crusade’s deviation to Constantinople. First, this study analyses the nature and scale of Venice’s undertaking, attempting to quantify and measure in economic terms the number of ships and passengers onboard, as well as the supplies’ weight and cost, for both men and horses. This analysis, based on analoguous contracts, proves the agreed sum of 85 000 silver marks was in no way exaggerated. Also, the analysis weighs the importance of such a sum in the economic context of the times, and tries to identify the reasons of the crusaders’ shortcomings. Despite a certain traditional historiography, this analysis demonstrates that Venice cannot bear the brunt of the responsibility for the Crusade’s deviation, and that blaming their uncompromisingness, their greed, or even their duplicity, is wrong. The sheer effort provided by the Republic, indicates it took every measure to warrant the venture’s success. The interruption of far-away trade, the construction of numerous ships, the requisition of thousands of sailors to man them, and the logistics needed to supply tens of thousands, display well the Venetians’ dedication. It is the crusaders’ failure to pay which triggered doge Enrico Dandolo to commit further, thus irremediably joining his city’s fortunes to those of the expedition.

The present thesis deals with the Byzantine Empire at the beginning of the 13th century. The text concentrates on events following the conquest of Constantinople by the crusader army in 1204 and the response of Byzantine elites to the new political reality. The main attention is paid to Theodore I Laskaris and his actions concerning the emerge of Empire of Nicaea. The Nicene Empire is compared to the Empire of Trebizond and the Despotate of Epirus. The purpose of the thesis is to analyze differences of these state units and their relation to the political and cultural tradition of the Byzantine Empire as well as to determinate main elements of the Byzantine statehood. The significant amount of both continuity of social processes and cultural traditions within the Byzantine society is emphasized. The Empire of Nicaea is evaluated as an integral and important part of the history of the Byzantine Empire.