Although after the death of the prophet Islam had first to fight for its very existence, and although it was only by desperate courage and energy that the revolting tribes were reduced to sullen submission, Mohammedanism had this singular power that it could cast a spell over its reluctant converts and convert them into fervent disciples. Moreover, when it spread beyond the borders of Arabia a new inducement was added to encourage loyalty. The Arabs became an aristocratic order with distinctive privileges, and although the equal brotherhood of all believers was preached in the Koran it was never practised as between the army from Arabia and the Syrians, Persians, Copts, in other countries. Apparently Mohammed had not contemplated its extension to alien races. Therefore the brotherhood of Islam was really the union of the Bedouin of the desert in equality of privilege and community of mutual service. The rule that required all the children of the faithful, whether from wives or concubines, to be brought up as Mohammedans with the full status of their fathers, led to the rapid growth of the army of Islam and its continual infusion with the renewing vigour of fresh blood. So this conquering host poured out spreading death and terror, always gathering spoil, and often exacting tribute.
When it looked beyond the borders of Arabia Mohammedanism found itself confronted by two great empires—Persia in the East and Rome in the North and West. United these two powers could easily have nipped the new terror in the bud. Even separately under normal circumstances either of them should have been more than a match for it. But at this most momentous juncture their century long enmity, which had sometimes slumbered for generations, had broken out into deadly feud.
A few years before the appearance of the new and totally unexpected danger, Chosroes the king of Persia had effected a successful invasion of the Roman Empire, first penetrating to Palestine and seizing Jerusalem. That city of unparalleled misfortunes was then given up to outrage and plundering, during which time thousands of monks,
