As the Byzantine Empire fell, Russia emerged as a powerhouse of Orthodoxy. Moscow began to view itself as the "Third Rome," inheriting the mantle of the protector of the faith. The Rise of National Churches
Cultural and theological drifts between Rome and Constantinople.
The "Rum Millet" system under Ottoman occupation.
The Apostolic Age and the rise of the Pentarchy.
To finalize your paper, you should consult and cite authoritative texts on this subject:
Istoria Bisericii Ortodoxe Române by Mircea Păcurariu — The definitive source if you are focusing specifically on the Romanian Orthodox Church context.
Between the 4th and 8th centuries, the Church held seven Ecumenical Councils. These gatherings were crucial because they formulated Christian dogma and combated heresies like Arianism and Iconoclasm.