This article sets out to determine the historical grounds for the rupture of Eucharistic communion between the Moscow and Constantinople Patriarchates. The method of historical genesis was used as a key research method, since it allows historical sources for the modern conflict between the Moscow and Constantinople Patriarchates, as well as the pattern of its manifestation to be identified. The article considers the entire history of relations between the Russian Church and the Patriarchate of Constantinople from the perspective of the ideological concept of the fall of Constantinople as the Second Rome. The historical reproducibility of interchurch conflict is established. The author refers to the history of Fanar’s hostility towards Russia and the Russian Church as new attractors of the formation of Orthodox civilization. The results of the study show that, in the history of the Constantinople Patriarchate, the Uniate precedent was not accidental and was manifested in the subsequent history of Fanar. The specific feature of this research consists in the projection of the centuries-old history of the Churches on the current inter-church conflict, relating the philosophy of the Third Rome to the realities of the historical process.