Kûfa and Bussorah, thus unique in their origin, had a singular influence on the destinies of the Caliphate and of Islam itself. The vast majority of the population came from the Peninsula, and were of pure Arabian blood. The tribes which, with their families, scenting from afar the prey of Persia, kept streaming into Chaldæa from every corner of Arabia, settled chiefly in these two cities. At Kûfa the races from Yemen and the south predominated; at Bussorah, from the north. Rapidly they grew into two great and luxurious capitals, with an Arab population each of from 150,000 to 200,000 souls.[306] On the literature, theology, and politics of Islam, these cities had a greater influence than the whole Moslem world besides. Service in the field was desultory and intermittent. The intervals of rest were spent in ennui. Excepting when enlivened by the fruits of some new victory, the secluded harems afforded their lords but little variety of recreation or amusement. Otherwise the time was whiled away in the converse of social knots; and in these, while they discussed the problems of the day, they loved still more to live in the past, and fight their battles over again. Hence tradition. But the debates and gossip of these clubs (to which we owe the two great schools of Bussorah and Kûfa) too often degenerated into tribal rivalry and domestic scandal. The people became petulant and factious; and both cities grew into hotbeds of turbulence and sedition. The Bedouin element, conscious of its strength, was jealous of the Coreish, and impatient at whatever checked its capricious humour. Thus factions sprang up which, controlled by the strong and wise arm of Omar, broke loose under weaker Caliphs, eventually rent the unity of Islam, and brought on disastrous days, which, but for its marvellous vitality, must have proved fatal to the Faith. CHAPTER XIX. CAMPAIGN IN NORTHERN SYRIA. A.H. XV. A.D. 636. [Sidenote: Abu Obeida’s advance on Northern Syria. End of A.H. XIV. A.D. 635.]