The dissertation is devoted to the problems of the perception of Muslims and the threat posed by the Ottoman by the Byzantine and East-European writers of the XV century. According to the materials of historical works analyzed the ratio of the authors to the representatives of the Islamic faith in a severe foreign situation and also domestic religious contradictions. Analysis of the works of Byzantine and Balkan writers allows us to trace the evolution of the views of historians on the matter and to reveal the extent of their bias. According to the Byzantine and East-European sources revealed the attitude of the authors of the XV century to the Turks and denoted points of contact of Christian and Muslim civilizations in the context of military confrontation, also investigated the attitude of the authors to the key events of the Turkish expansion in the XV century - Battle of Varna in 1444 and the capture of Constantinople in 1453. The dissertation also addresses the problem of mutual Christians and Muslims considered in the interpretation of the writers and the question of the possibility of cultural and religious dialogue between the warring parties.