Original sentence: The reign of Charlemagne in Western Europe is particularly noted for bringing the last major Christian tribes outside of the unified Church into communion with the Roman Church (through conquest).While in the West Christianity struggled with the so-called orthodox Roman Church competing against the Arian Christian and pagan faiths of the Germanic rulers, the Eastern Romans spread Christianity to the pagan Slavs establishing the Church in what is now Russia and Eastern Europe
Edited sentence: The reign of Charlemagne in Western Europe is particularly noted for bringing the last major Christian tribes outside of the unified Church into communion with Rome (through conquest).While in the West the Church gradually converted the Germanic tribes from Arianism and paganism to the so-called orthodox faith, the Eastern Romans spread Christianity to the pagan Slavs establishing the Church in what is now Russia and Eastern Europe