The Greek Church has not lacked missionary zeal. Through her agency the barbarians who entered southeastern Europe during the early Middle Ages were converted to Christianity. At the present time nearly all the peoples of the Balkan peninsula, including Greeks, Montenegrins, Serbians, Bulgarians, and Rumanians, belong to the Greek Church. [34] Its greatest victory was won toward the close of the tenth century, when the Russians were induced to accept the Greek form of Christianity. Outlying branches of the Greek Church are found also in the Turkish Empire. It now includes about one hundred and thirty-five million adherents in European lands. PRESENT ORGANIZATION OF THE GREEK CHURCH The patriarch of Constantinople is the spiritual head of the Greek Church. He enjoys, however, no such wide authority over eastern Christians as that exercised by the pope over all Roman Catholics. There are as many as sixteen branches of the Greek Church, each self-governing and under its own officers. Despite the local independence of its branches, the Greek Church remains unified in doctrine. It claims to be the only "Orthodox" church and clings with almost Oriental conservatism to the traditions of earlier ages. Nevertheless, as the official church of Russia, the largest and most swiftly growing of European countries, the Greek Church has before it a future of great importance. 129. THE ROMAN CHURCH THE ROMAN CHURCH PROGRESSIVE The separation of eastern and western Christianity naturally increased the importance of the Papacy. The popes henceforth had a free hand to guide the destinies of the Roman Church. That church under their direction was to show itself vigorous and progressive, with a wonderful power of adaptation to new and changed conditions. THE ROMAN CHURCH SURVIVES THE EMPIRE The Roman Empire in the West had gone down before the assaults of the Germanic barbarians, but in its place had arisen a new creation--the Roman Church. The chief city of the old empire became the capital of the Papacy. The pope took, and has since retained, the title of Supreme Pontiff (_Pontifex Maximus_), once given to the head of the Roman state religion. [35] Latin has continued to be the official language of Roman Catholicism. The Roman genius for law and government found a new expression in the creation of the papal power. The true successors of the ancient Roman statesmen were the popes of the Middle Ages. The idea of Rome, of her universality and of her eternity, lived on in the Roman Church. WORK OF THE ROMAN CHURCH