The monograph, based on a study of written sources and data from archaeological studies of medieval cities and castles of Crimea, presents a historical reconstruction of the relationship between the Genoese Kaffa and the Principality of Theodoro (the last "fragment" of the Byzantine Empire), which developed between two participants in the ethnocultural dialogue in the territory of Gazaria in the XV century. The material presented in the monograph allows not only to answer some of the questions posed earlier, but also to determine the prospects for further research into the political history of Tauris of the 15th century. For historians, archaeologists, museum workers and students of historical faculties.