engaged in combat, and in one day the Persian army was routed, and its leaders slain (May-June 637).
And now the fertile black land (Sawād) of 'Irāḳ lay open to the Arabs. Conditions exactly similar to those in Syria caused the Aramaic peasants to greet the Arabs as deliverers. Without meeting with any noteworthy opposition the Saracens pushed on as far as the Tigris, whither they were attracted by the rich treasures of the Persian capital Ctesiphon, or as the Arabs called it the "city-complex" or Madā'in. The right bank of the Tigris was abandoned and the floating bridges broken up. A ford having been disclosed to the Arabs the residue of the garrison followed in the wake of Yezdegerd and his court, who immediately after the battle had sought the protection of the Iranian mountains. The city opened its gates and fabulous booty fell into the hands of the Arabs. After a few weeks of quiet and no doubt somewhat barbaric enjoyment, they had again to make one more stand on the fringe of the mountains at Jalūlā; this also ended victoriously for them, and with that the whole of 'Irāḳ was thus in their hands. Here also it was no matter of chance that the expansion of the Arabs first came to a standstill at the mountains, where the line was drawn between the Semitic and the Aryan elements of the population. Only the province of Khūzistān, the ancient Elam, caused some trouble still. Hither the Arabs appear to have proceeded from the south of the marsh district, when the insignificant raids of the boundary tribes there, encouraged by Medina, assumed after the battle of Ḳādisīya a more serious character, starting from the newly founded base at Baṣra. The chief seat of government was not placed at Ctesiphon, but, by express command of the Caliph, at Kūfa (near Ḥīra): and this was developed into a great Arabian military camp, intended to form the main citadel of Muslim Arabianism as against foreign Persian culture. Later the ancient Baṣra attained an independent position alongside of Kūfa. The rivalry of the two places sets its impress both on the politics and on the intellectual life of the following century.
It was not until after these stupendous victories of Yarmūk and Ḳādisīya that the great Arabian migrations assumed their full development, for now even those tribes who were but little disposed to Islām were compelled to wander forth in order to seek their happiness in those cultivated lands which as rumour told them were only to be compared with Paradise itself. Now it was that the momentous change took place to which reference has been made at the outset; now it was that Islām no longer represented dependence on Medina, as it did in the time of Mahomet and Abū Bakr, but from this time forward it represented the ideal of the common universal empire of the Arabs. And at this stage the further expeditions became systematic conquests, in which usually whole tribes participated. A first step in this direction was to round off the empire, combining the Syrian and 'Irāḳ provinces by
