The collapse of the Byzantium Empire did help challenge the balance of power in ecclesiastical, with the years preceding 1453 seeing a temporary reconciliation of the Ecumenical Patriarchate of Constantinople and the Catholic Church. Hoping to win support from the West to prevent Constantinople from falling into Ottoman hands, the Eastern Orthodox Church temporarily agreed to the bull Laetentur Caeli (Let the Heavens Rejoice) in 1439 that briefly ended the four-hundred-year schism between the churches of Rome and Constantinople. However, it was never accepted by the Russian Orthodox Church, and the reunion was soon repudiated by the Eastern Orthodox Church.

However, the temporary truce between the Catholic and Orthodox Churches did leave a significant mark both in the East and the West. For Rome, it allowed Pope Eugene IV to secure his position as head of the Catholic Church against the Conciliarist Movement, a group that sought to invest greater ecclesiastical power in ecumenical councils as opposed to the papacy. With Pope Eugene IV able to push for the reunion of the Eastern and Western Churches as the Conciliarists met at the rival Council of Basel, he was able to demonstrate the importance of the papacy in uniting Christendom.

Laetentur Caeli also gives ecclesiastical historians one of the earliest signs of tensions between the Russian Orthodox Church and Constantinople. Moscow’s decision to reject the Council of Florence can partly be explained by concerns about being forced to accept Catholic dogmas around purgatory, the eucharist, and the papacy. Yet political aspirations may have also played a role, or so argues Serhii Plokhy. The letter sent from Moscow to Constantinople rejecting the Council of Florence was sent not by Muscovite clergy, but by the Grand Prince of Moscow, Vasilli II, who had also been lobbying to select his own candidate for the position of Metropolitan of Moscow. With Moscow finding it unacceptable to compromise on its theological divisions with Rome, and seeking greater control of the Russian Orthodox Church, the Council of Florence helped encourage Moscow to assert its own position as an Orthodox power.

There are other consequences that came about because of the Fall of Constantinople, although ecclesiastical history is my primary area of expertise so I will not comment on these. However, I have shown that the weakened state of the Byzantine Empire in the years immediately preceding 1453 forced the Ecumenical Patriarchate of Constantinople to beg for outside assistance, even at the cost of suspending the Great Schism with Rome. This in turn strengthened the power of Rome over the Conciliar Movement and pushed Moscow to assert its own ecclesiastical position in the Eastern Orthodox Church.

Sources:

Primary: Laetentur Caeli (Florence: Council of Florence, 1439)

Secondary: Hosking, Geoffrey, Russia and the Russians, 2nd edn (London: Penguin Books, 2012), pp. 81-82.

Plokhy, Serhii, Lost Kingdom, 1st edn (London: Penguin Books, 2018) pp. 21-23.

Tanner, Norman, “Medieval Ecclesiology and the Conciliar Movement” in Oxford Handbook of Ecclesiology, 1st edn (Oxford: Oxford University Press, 2018), pp. 212-214.