Persian detachments were posted in Mesopotamia and the outskirts of the desert at Anbâr, Ain Tamar, and other places, within easy distance of Hîra, and against these Khâlid now directed his steps. Leaving Cacâa, a warrior of the Beni Temîm, in command at Hîra, he laid siege to Anbâr, a fortress on the left bank of the Euphrates, some eighty miles above Babylon. The garrison, though galled by the Moslem archery, were secure behind their strong walls and the deep fosse by which it was surrounded, until Khâlid, by a stratagem, stormed an entrance. He slew the old and worn-out camels of his force, and casting their carcases into the ditch, thus forced his way across. [Sidenote: and Ain Tamar.]The Persian governor sued for terms, and was allowed to retire.[131] Anbâr and the richly-irrigated neighbourhood of Felûgia[132] thus secured, Khâlid went on to Ain Tamar, on the desert border, three days west of Anbâr. The Persian governor Mihrân had there, besides the imperial troops, a great following of nomad tribes, and among these the Beni Taghlib, who (a strange coincidence) were under command of Ackka, Hodzeil, and other chiefs, the captains of the prophetess Sajâh when she invaded Yemâma.[133] These, advancing to the attack, assailed Khâlid as he approached the citadel; but he repulsed them easily, taking Ackka prisoner with his own hand. Mihrân, seeing the rout from the ramparts, fled, and left the garrison and the fugitives to defend themselves as best they could. Refused terms and reduced to straits, they surrendered at discretion. [Sidenote: Khâlid’s severity.]Khâlid, angry at the persistent opposition of the Mesopotamian tribes, and also at his loss in the field (for though the victory was easy, a Companion of note and a Citizen of Medîna were among the slain), was betrayed into an unwise severity which embittered the Christian Bedouins against him.[134] Ackka was beheaded in front of the city walls; the garrison was then led forth, every adult male put to death, and the women, with the children, made over to the soldiers or sold into slavery. In a cloister, hard by the church, were forty youths, who, in their terror, barred the door upon the enemy. [Sidenote: Forty Christian students taken captive.]When their retreat was forced open, they gave themselves up, declaring that they were students, receiving there instruction in the Gospel. Their lives were spared, and, being of a superior class, they were distributed among the leaders. It is hard to record the fate of these youthful scholars snatched from the Nestorian Church to be brought up as captives in the Moslem faith. But the fate, though sad, could hardly have been singular in the rough and sanguinary tide of Saracen invasion. Special prominence has, no doubt, been given to it here because Sirîn, one of the youths, became the father of Mohammed, the famous Moslem doctor of Bussora, and Noseir, another, the father of Mûsa, the not less famous conqueror of Spain.[135]