The Orthodox Church: An Introduction To Its His... -

The Church flourished under the Byzantine Empire, influencing law, art (icons), and architecture (Hagia Sophia).

In the 9th and 10th centuries, Cyril and Methodius brought Orthodoxy to the Slavic peoples, leading to the eventual conversion of Russia in 988 AD.

Tensions between the Greek-speaking East and the Latin-speaking West grew over centuries due to cultural, political, and theological differences.

The Orthodox Church views itself as the continuation of the original Church founded by Jesus Christ. Its history began in Jerusalem on the Day of Pentecost. For the first thousand years of Christianity, the East and West were generally united under the "Pentarchy"—five major episcopal sees: Rome, Constantinople, Alexandria, Antioch, and Jerusalem. The Great Schism (1054)