Abstract
After securing their first fortress on European soil in 1352, the Ottomans rapidly expanded throughout the Eastern Balkans. Due to the unfavourable internal situation, the Christian Balkan states did not possess a sufficient force to defend themselves, and the Byzantine Emperor Manuel II Palaiologos had to rely on his diplomatic skills to and personally visited Western Europe in order to acquire an alliance against the Muslim enemy.
However, The Emperor did not dispatch diplomatic missions only to the West but to the lands of Rus' as well. In contrast to the western embassies, the prestige and position of the Ecumenical Patriarch of Constantinople also played a significant role - the patriarch addressed a letter to Vasily I Dmitriyevich, the Grand Prince of Moscow, together with Manuel II.
The purpose of this mission was probably not to sign a treaty of alliance but rather ask for a financial assistance. This goal was sufficiently fulfilled - the Grand Prince of Moscow and princes of Ryazan, Tver and Lithuania agreed to join the effort to fund Constantinople's defence.
Altogether, roughly 20 thousand of silver rubles were raised by both clerics and laity and subsequently sent in Constantinople during the year of 1398. The gift was amicably received in the city on Bosporus and its citizens repaid this act of kindness with icons, presents and saints' remains.
Further contacts followed, primarily through the efforts of the Ecumenical Patriarch. While Manuel was in Western Europe, the patriarch dispatched another mission to Russia to the Metropolitan of Kiev and All Russia Cyprian who maintained correspondence with the patriarch.
Based on the research of correspondence and Russian narrative sources, the present paper analyses the possibilities of Russian assistance to the declining Byzantine state and the results of the mission from the perspective of both the Russian principalities and the Byzantine Empire.