After his victory, Sád, by desire of the Caliph, paused for a little on the field of Câdesîya, and allowed the weary troops to rest. Fragments of the great Persian host escaped, broken and dispersed, in the direction of the ruins of Babylon, and rallied there, on the right bank of the Euphrates. After two months’ repose, Sád, now recovered from his sickness, advanced to attack them. One or two short marches brought him to Hîra. It was the third time the unfortunate city had been taken and retaken. The punishment for this its last helpless defection from the Moslem cause, was the doubling of its tribute. Soon supplanted by Kûfa, at a few miles’ distance, the once royal city speedily dwindled into a common village. But the neighbouring palace of Khawarnac, the beautiful residence of the Lakhmite princes, was left standing on the lake of Najaf, and was sometimes visited, as a country seat, by the Caliphs in after days. [Sidenote: The Persians driven across the plain to Madâin, and the Sawâd reoccupied.] As the Moslems advanced, the Persian troops made a stand, first at Birs Nimrûd,[280] and then, recrossing the Euphrates, under the great mound of Babylon. Driven from thence with loss, they fell back upon the Tigris. Sád then pitched a standing camp at Babylon, and, himself remaining there, sent forward his lieutenants, Hâshim and Zohra. [Sidenote: A.H. XV. A.D. 636.] These, in a series of minor but decisive engagements, cleared the plain of Dura, here about fifty miles broad, from the Euphrates to the Tigris.[281] The territorial chiefs from all sides came in, tendering their allegiance, some as converts, some as tributaries; and the Arabs again became undisputed masters of the whole _Sawâd_, with the channels and canals intersecting it. Several months thus passed; and at last, in the summer of A.D. 636, Sád found himself able, now with the full consent of Omar, to make an advance upon Medâin.[282] [Sidenote: The queen-mother is discomfited.]