Researches of inter-cultural and inter-confessional communication under the circumstances of military and religious confrontation, built on concrete historical materials, contribute to the study of the establishment mechanisms of cross-cultural communication in extreme situations, to the determination of the pattern of use of the “image of the enemy” by the authorities for the mobilization of a society torn by internal contradictions, and to the identification of cases of tolerance, religious in particular. The project addresses the problem of studies in inter-civilizational conflict between the Greeks and the Turks at the final stage of the Ottoman conquest of Byzantine lands. This project is aimed at the analysis of specific features of socio-political, ideological, and religious situation in Byzantine cities under extreme conditions of Ottoman sieges in the late fourteenth and the first third of the fifteenth centuries. The project authors will focus their attention on most important events of the Late Byzantine Period: three sieges of Constantinople (1394-1402, 1411, 1422) and two sieges of Thessalonike (1383-1387, 1422-1430). The study of event-context of the said sieges, their role in the acceleration of the Byzantines’ military-political and idea-religious resistance to the Ottomans, and the aggravation of social and internal political tension within Byzantium seem principally important for modern Byzantine Studies. Addressing the problem of the Byzantine society’s reaction on the stress situation of Ottoman sieges, which not only increased anti-Turkish feelings of the society, but also uncover internal contradictions within the Late Byzantine society, would allow the authors to develop new ideas concerning process of demise of the Byzantine Empire. The results of the research could enhance the understanding of specific features of the social and political crises in Late Byzantium, and to enlarge the notion of particulars of Byzantine-Ottoman confrontation.