This amazing success was due to a number of contributing factors, chief among them being the character of the Arab race, the nature of Mohammed's teaching, and the general state of the contemporary Eastern world. Undistinguished though the Arabs had hitherto been, they were a people of remarkable potentialities, which were at that moment patently seeking self-realization. For several generations before Mohammed, Arabia had been astir with exuberant vitality. The Arabs had outgrown their ancestral paganism and were instinctively yearning for better things. Athwart this seething ferment of mind and spirit Islam rang like a trumpet-call. Mohammed, an Arab of the Arabs, was the very incarnation of the soul of his race. Preaching a simple, austere monotheism, free from priestcraft or elaborate doctrinal trappings, he tapped the well-springs of religious zeal always present in the Semitic heart. Forgetting the chronic rivalries and blood-feuds which had consumed their energies in internecine strife, and welded into a glowing unity by the fire of their new-found faith, the Arabs poured forth from their deserts to conquer the earth for Allah, the One True God. Thus Islam, like the resistless breath of the sirocco, the desert wind, swept out of Arabia and encountered--a spiritual vacuum. Those neighbouring Byzantine and Persian Empires, so imposing to the casual eye, were mere dried husks, devoid of real vitality. Their religions were a mockery and a sham. Persia's ancestral cult of Zoroaster had degenerated into "Magism"--a pompous priestcraft, tyrannical and persecuting, hated and secretly despised. As for Eastern Christianity, bedizened with the gewgaws of paganism and bedevilled by the maddening theological speculations of the decadent Greek mind, it had become a repellent caricature of the teachings of Christ. Both Magism and Byzantine Christendom were riven by great heresies which engendered savage persecutions and furious hates. Furthermore, both the Byzantine and Persian Empires were harsh despotisms which crushed their subjects to the dust and killed out all love of country or loyalty to the state. Lastly, the two empires had just fought a terrible war from which they had emerged mutually bled white and utterly exhausted.