At the Origins of the Union of Florence: Byzantium, Sigismund of Luxembourg, and the Antipope John XXIII

This article addresses historical circumstances under which the negotiations on the church union between Byzantium and Latin West started in the fifteenth century. The author finds the origins of the process in a letter from the Hungarian King Sigismund of Luxembourg to the Byzantine Emperor Manuel II Palaiologos. According to the most recent scholarship, it appeared in the first half of 1412. Taking the analysis of the source into account, it has been concluded that the King’s initiative, which called the Eastern Emperor to take joint action against the Turks in addition to the idea of the union of churches, was not the result of the Byzantine Empire’s appeal for help. Although Byzantium was experiencing an acute crisis in relations with the Ottomans at that time, the author of the article proves that the goal of the eastern ruler was an agreement with one of the representatives of the Ottoman dynasty. The obstacle to the agreement was the conflict between King Sigismund and Venice. The researcher assigns a special place in the said conflict to the Pope elected at the Council of Pisa, following which Sigismund got chances for the imperial crown. In this regard the participation of Byzantium in the relations of the “Pisan” Antipope John XXIII with Venice and the Hungarian King has been revealed. The author has determined the time and method of introducing the idea of the church union into the diplomatic process and has come to the conclusion that it became possible in result of the temporary coincidence of the interests of the Pope and the Emperor in the unfolding conflict. From the analysis of the international situation and actions of Byzantine diplomacy there are reasons to suppose that Byzantium viewed the union as the form to declare neutrality and the instrument of mediation in relations with Western states. It was the way to prevent their military intervention in the situation in the East and, in result, the condition for the survival of the Empire on the principles of peaceful coexistence with the Turks.