Indeed, so far from the development of the Christian Church being hampered by the establishment of Muhammadan rule, the history of the Nestorians exhibits a remarkable outburst of religious life and energy from the time of their becoming subject to the Muslims.^[2]

Alternately petted and persecuted by the Persian kings, in whose dominions by far the majority of the members of this sect were found, it had passed a rather precarious existence and had been subjected to harsh treatment, when war between Persia and Byzantium exposed it to the suspicion of sympathising with the Christian enemy.

But, under the rule of the caliphs, the security they enjoyed at home enabled them to vigorously push forward their missionary enterprises abroad. Missionaries were sent into China and India, both of which were raised to the dignity of metropolitan sees in the eighth century; about the same period they gained a footing in Egypt, and later spread the Christian faith right across Asia, and by the eleventh century had gained many converts from among the Tatars.^[3]

If the other Christian sects failed to exhibit the same vigorous life, it was not the fault of the Muhammadans. All were tolerated alike by the supreme government, and furthermore were prevented from persecuting one another.^[4]

In the fifth century, Barsauma, a Nestorian bishop, had persuaded the Persian king to set on foot a fierce persecution of the Orthodox Church, by representing Nestorius as a friend of the Persians and his doctrines as approximating to their own; as many as 7800 of the Orthodox clergy, with an enormous number of laymen, are said to have been butchered during this persecution.^[5]

Another persecution was instituted against the Orthodox by Khusrau II, after the invasion of Persia by Heraclius, at the instigation of a Jacobite, who persuaded the King that the Orthodox would always be favourably inclined towards the Byzantines.^[6]

But the principles of Muslim toleration forbade such acts of injustice as these: on the contrary, it seems to have been their endeavour to deal fairly by all their Christian subjects: e.g. after the conquest of Egypt, the Jacobites took advantage of the expulsion of the Byzantine authorities to rob the Orthodox of their churches, but later they were restored by the Muhammadans to their rightful owners when these had made good their claim to possess them.^[7]