Her grandson, Vladimir of Kiev, made Rus' officially a Christian state.

Despite the politically motivated murders of Mikhail of Chernigov and Mikhail of Tver, the Mongols were generally tolerant and even granted tax exemption to the Church.

Such holy figures as Sergius of Radonezh and Metropolitan Alexis helped the country to withstand years of Tatar oppression, and to expand both economically and spiritually.

New sects sprang up, some of which showed a tendency to revert to Mosaic law: for instance, the archpriest Aleksei converted to Judaism after meeting a certain Zechariah the Jew.

In the 1540s, Metropolitan Macarius codified Russian hagiography and convened a number of church synods, which culminated in the Hundred Chapter Council of 1551.

The reign of Ivan III and his successor was plagued by a number of heresies and controversies.

One party, led by Nil Sorsky and Vassian Kosoy, called for the secularisation of monastic properties.

In 1439, at the Council of Florence, some Orthodox hierarchs from Byzantium as well as Metropolitan Isidore, who represented the Russian Church, signed a union with the Roman Church, whereby the Eastern Church would recognise the primacy of the Pope.

However, the Moscow Prince Vasili II rejected the act of the Council of Florence brought to Moscow by Isidore in March 1441.

The ROC, as well as the primate thereof, officially ranks fifth in the Orthodox order of precedence, immediately below the four ancient Patriarchates of the Greek Orthodox Church, those of Constantinople, Alexandria, Antioch, and Jerusalem.