Greeks and Russians
When the Kievian Rus converted to Christianity Constantinople won a powerful ally. This alliance strengthened the Byzantine Empire and helped it survive for some more centuries by pacifying its northern border. To the Rus it gave unity and, for the first time, a real identity. Till then they had been torn between Slav rites and habits, other pagan rites, and the influence of the Viking (Rurik) dynasty ruling them. The alliance with Constantinople led to an influx of scholars and artists from all over the Byzantine Empire. The civilian city culture rose to a level unknown hitherto, and the political-military aspect should not be underestimated: It secured the southern frontier of the Rus and gave them the opportunity to establish themselves in the region. The only serious threat now came from the western border, from Lithuania and Poland. This was to a great extent due to the emerging antagonism towards the Roman-German Empire, the alliance of the German rulers and the Pope.
The Kievian Rus never saw a reason to emancipate itself from the Byzantine Empire. It remained under the Patriarchate of Constantinople.
When the Mongolians destroyed Kiev nearly completely, and also other cities of the Rus, the only source of identity that remained was the religious and cultural alliance with Constantinople. For more than a century the Russian church was busy with infighting, fighting heresy and trying to establish unity. Meanwhile, first the city-empires, successor states of the Rus fought against each other, often with the help of the Mongolians.
Then Constantinople, already visibly debilitated for a certain time, fell to the Ottomans in 1453.
But that was the time when Russia started to reunite, under the reign of Grand Duke Vassili and his son, the first (Muscovitie) Tsar Ivan IV (the Terrible). The fall of Constantinople gave the Russian Empire further legitimation to assume the role of the successor of Constantinople which had called itself for a short time called ”New Rome“ : Moscow felt itself entitled to play the role of a successor of ”real faith“ , thus it claimed to be the ”Third Rome“ . In terms of the orthodoxy, this has a certain legitimation even today: it is the biggest orthodox state, at least by inhabitants – perhaps not by believers, as there is an atheist legacy from Soviet times, and Russia has many religious minorities: Muslims, Shamanists, Buddhists. But the Russian orthodox church is gaining followers day by day.
A man on the Crimea who was very religious once tried to convince me of his point of view, back in the 90-ies. Perhaps this also refers to the time of the Mongolian yoke: ”Look what has happened, he said. The state has fallen apart, but God has remained!“
The reunification of the Russian lands was both a precondition and a result of the strive for unity within the church.
In a desperate attempt to gain allies against the pressure of the Ottoman Empire some prominent Greek church authorities declared the unification of the Eastern churches with the Church of Rome at the Council of Florence in 1439. In vain, as Constantinople was still left to itself and was conquered a few years later. The Russian clergy rejected this decision, which had no influence on other orthodox churches, either. As a consequence the Russian church elected an own metropolitan in 1448 which then led the Russian church affairs independently from outside influence. An own Russian Patriarchate was established during the regency of the later tsar Boris Godunov in 1589, the first Muscovite patriarch being consecrated by the the representative of the over-all orthodox church, patriarch Jeremy from Constantinople.