The Eastern or Greek Church, having the Patriarch of Constantinople as its head, and the national Churches of Russia, Romania, etc. in communion with it. Separation from the Western Church came in the 4th century, originally through cultural and political factors, focused from the 5th century onwards on differences of doctrine and ritual, and took formal effect in 1054 when the Pope and the Patriarch of Constantinople excommunicated each other. In the latter part of the 20th century the Orthodox Churches have taken an active part in the ecumenical movement; the mutual excommunication of 1054 was abolished in 1965.