The elation produced by Heraclius' stunning success was to prove short-lived. In 630, two years after the True Cross had been restored in triumph to Jerusalem, a former merchant entered the Arabian city of Mecca at the head of an army of Bedouin followers. By the death of the prophet Muhammad in 632 the Arabian peninsula was united behind the new faith which he had preached, and within ten years Persia and the Byzantine provinces of the east had succumbed to Islam.

The phenomenal success of this new movement had its roots in the volatile political, social, and religious climate of Arabia. Tensions had grown between the Bedouin tribesmen and the merchants of the wealthy towns, and the old polytheistic beliefs had been undermined by the monotheistic certainties of Judaism and Christianity. The lid which had been kept on the Arabs' inveterate raiding and political turmoil by Byzantine and Persian diplomacy was removed by the struggle between the superpowers. Muhammad's genius lay in gaining control of this maelstrom by his statesmanship and his powerful yet eclectic vision of an ideal of total submission (Islam) to Allah, and channelling the traditional warlike energies of his people and their new-found fanaticism into an irresistible movement of conquest.

Islam owed its remarkable success both to its own strengths and to its opponents' weaknesses. The prowess and dedication of its warriors, the ability of the early caliphs, the simple appeal of its doctrines, and its proselytizing vigour with its promise of specific rewards all played their part. In contrast with earlier invaders, the Arabs were able to evolve an original and durable synthesis. They took over the more effective and appealing tenets of other faiths and retained viable elements of GraecoRoman administration and urban culture while maintaining the distinctiveness and vitality of their own culture. Also important was the political and religious alienation of many of Byzantium's subjects. Coptic- and Aramaic-speaking Monophysites in Egypt and Syria saw their Arab fellow Semites as deliverers from Greek tax-gatherers and orthodox persecutors, and both Christians and Jews were treated with toleration in return for the payment of a head-tax. Signifi-

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