The Eastern Orthodox Church is a body of Christians that claims origins extending directly back to Jesus Christ and his Apostles through unbroken Apostolic Succession. Its doctrines were formalized through a series of church councils, the most authoritative being the Seven Eucemenical Councils held between the 4th and 8th centuries. These councils were convened out of the necessity to resolve conflicts that had developed concerning beliefs such as Arianism, Nestorianism, and Monothelitism. Toward the end of its first thousand years of existence, differences developed between the Church in the Eastern and Western Roman Empire that ultimately led to the Great Schism in 1054 AD, dividing Christianity into Western Catholicism and Eastern Orthodoxy. Based on numbers of adherents, Eastern Orthodoxy is the second largest Christian communion in the world after the Roman Catholic Church, and the third largest grouping overall after Protestantism. There are approximately 215 million Eastern Orthodox Christians worldwide.
The present-day influence of the Eastern Orthodox Church encompasses the territories associated with the former Byzantine and Russian empires: Eastern Europe, Asia (Russia/Siberia), and parts of the Middle East and Africa. Today, although Eastern Orthodoxy's strongest influence can be seen in Greece, Cyprus, Russia, Ukraine, Belarus, Serbia and Montenegro, the Republic of Macedonia, Bosnia and Herzegovina, Bulgaria, and Georgia, the Orthodox Church has a presence in a great many other countries largely because of emigration of Eastern Orthodox peoples, with large communities in the US, Canada and Australia.