The Autocephaly of the Russian Church According to Byzantine Sources of the 10th Century from the Collection of the Österreichische Nationalbibliothek

The important information on the early jurisdiction of the Russian Church is contained in the letter of Bishop Leo of Synada (937–1003) to the anonymous Metropolitan of Ephesus (Cod. Vindob. Phil. Gr. 342, fol. 163v, 166v–167v) from the collection of the Österreichische Nationalbibliothek. The Vienna manuscript has already been described in detail in a number of works, but its analysis in relation to the realities of the time of the Baptism of Rus' has not yet been undertaken. Moreover, the letter has been erroneously attributed to Metropolitan Theodore II of Ephesus (989 (984?) – 1018 (1019)). The fact that the autocephalous Kyivan Church was established at the time of the Baptism of Rus' by Vladimir the Saint, together with the Metropolitan of Ephesus, called "head of the Church" in an 11th-century Greek manuscript from the collection of the Österreichische Nationalbibliothek, is reflected in the treatise of Archimandrite Nilus Doxopater, "The Order of the Patriarchal Sees" (Τάξις τῶν πατριαρχικῶν θρόνων), c. 1143.