Examination of the rich and complex relations between Western Europe, Byzantium, and the Islamic world from the early Islamic conquests of Christian lands in the seventh century to the Ottoman conquest of Constantinople in the fifteenth; comparison with the parallel historical development of the Christian polities in Western Europe, the Byzantine empire, and the Islamic states; exploration of their political, economic, and cultural interaction across space and time; emphasis on trade networks and commercial exchanges, court diplomacy and religious polemics.