point of dissolution, revived again under Heraclius, who after an arduous but successful war recovered from Persia the lost provinces. By that time, however (A.D. 629), the Prophet of Medina was already causing trouble on the frontiers of Arabia. Heraclius' attempt to regulate Church matters in Syria and the East had only time to show that the breach was irreconcilable. When the Moslem outburst came a few years later it found the Roman Empire exhausted by a long and desperate struggle, the buffer-state by which it had maintained its influence in Arabia destroyed, and the bulk of the Syrian Arabs, whatever may have been the sincerity of their Monophysite belief, at any rate opposed to the official orthodoxy of Byzantium.

MESOPOTAMIA

To the north-east of the peninsula of Arabia lay another Christian district, partly within the Roman Empire, but principally within the bounds of Persian dominion. A good deal of legend hangs around the introduction of Christianity to Edessa and the country of the Euphrates and the Tigris. But we can safely say that by the end of the third century there was a flourishing Church at Edessa, and that Christianity had already spread down the Euphrates valley and across the Tigris.1 There were churches at Nisibis, Arbela, Junde-shapur, Kashkar, and at Seleucia-Ctesiphon, the winter capital of the Persian kings, which ultimately became the seat of the Katholikos or

Patriarch of the Nestorian Church. More than once the Church within the Persian Empire had to suffer bitter persecution. Sometimes impelled by suspicion of sympathy between its Christian subjects and the rival Empire of Rome, sometimes stirred by the jealousy of the priests of the Magian religion, and sometimes from mere whim, the Persian Government raged cruelly against it. Nor was it altogether without its doctrinal troubles. But the Syrian type of thought maintained itself, except in Edessa, which was in Roman territory, and from which the supporters of the "two-nature" view of the Person of Christ were violently driven. Within the Persian Empire this type of doctrine prevailed, and taking its name from the deposed patriarch of Constantinople, the Church became definitely Nestorian. This separation in doctrine from the Church of the Roman Empire had at least the advantage of easing to some extent the relations of the Christians with the Persian authorities. In spite of its troubles the Church in those regions had a worthy history. By the end of the sixth century it had extended and deepened its hold so that probably no town of any size remained which had not its church and its bishop.

To what extent the people thus converted to Christianity were Arabs it is impossible to say. The situation here as regards relations between the settled and the nomad population was no doubt much the same as in Syria, and it seems reasonable to suppose that a proportion of the Christians of Mesopotamia were Arabs. Christianity also found its way into the actual territory