its overlord, whilst the Arab kingdom of Hira acknowledged the Persian king. Somewhere between A.D. 604 and 610, when the first beginnings of persecution were falling on the Prophet in Mecca, the Arabs led by al-Mondir inflicted a crushing defeat upon the Persian army under King Khusraw Parwiz, who, a few years before, had led a victorious force to the invasion of the Byzantine province of Syria. This victory showed the Arabs that, in spite of its imposing appearance, the Persian Empire, and presumably the Byzantine also, were vulnerable, and a determined effort might easily place the wealth of both at the disposal of the Arabs.
The Muslim conquests of the 7th century A.D. form the last of a series of great Semitic outspreads of which the earliest recorded in history resulted in the formation of the empire of Babylon some 2225 years before the Christian era. In all these the motive power lay in the Arabs who represent the parent Semitic stock, the more or less nomadic inhabitants of the barren highlands of Western Asia, who have always tended to prey upon the more cultured and settled dwellers in the river valleys and on the lower slopes of the hills.
"The belts between mountain and desert, the banks of the great rivers, the lower hills near the sea, these are the lines of civilization (actual or potential) in Western Asia. The consequence of these conditions is that through all the history of Western Asia there runs the eternal distinction between the civilized
