The Umayyad Caliph at last recognised the gravity of the situation, and sent all the forces he could muster to oppose Kahtaba. But the Hāshimite troops carried all before them. They defeated a large Syrian army near Isfahān, and captured the important stronghold of Nahāvend, A.H. 132 (749). Then Kahtaba started for Kūfa, making a slight detour to avoid Ibn Hobayra, who was encamped at Jalūlā. On reaching the Euphrates, Ibn Hobayra came up with him, and a battle ensued at nightfall near Kerbelā. Kahtaba perished,[178] but his son Hasan continuing the fray defeated Ibn Hobayra, and drove him back on Wāsit. Meanwhile the Yemenites revolted in Kūfa, and on the arrival of the victorious Hāshimite forces[179] delivered up the town to them. On the entry of Hasan ibn Kahtaba into Kūfa the head of the `Abbāsid house, Abū-l-`Abbās, emerged from his hiding-place, and the town for the time became the seat of the `Abbāsids. Abū Sālama was provisionally recognised as the Vezīr of the house of Mohammed. Meanwhile the fate of the Umayyads had been decided by the battle of the Zāb in Mesopotamia, A.H. 132 (750), where Merwān himself, surrounded by his greatest generals, encountered the Hāshimites under `Abdullah, Abū-l-`Abbās’s uncle. Merwān suffered a crushing defeat, and fled, hotly pursued, to Egypt, where he was finally captured and slain. At the beginning of this year Abū-l-`Abbās, called Es-Saffāh, or the “Shedder of Blood,” was proclaimed Caliph in the great mosque of Kūfa. The new Caliph’s first measure was to sweep the entire Umayyad race from the face of the earth. The traditions which have come down to us of his butcheries pass all belief.[180] Syria was soon reduced, and Ibn Hobayra surrendered his last retreat, Wāsit. But troubles continued throughout his reign. Abū Muslim’s attempts to put all the Umayyad faction to the sword led to a serious rising in Khorāsān. The partisans of the fallen dynasty, in Bokhārā, Soghdiana, and Farghāna, aided by the emperor of China, took the field in force, but were soon dispersed with great slaughter by Ziyād, governor of Samarkand. “It is plain,” says Vambéry,[181] “from the historical sources before us that the original Iranian population of the land, namely, the Tājiks, fought under the banner of Nasr, and long remained true to the cause of the Ommayades.” “The resistance which Nasr ibn Sayyār offered not only to the superior force, but also to the allurements of Ebu Muslim, deserves our respect.” “On the other hand, the adroitness of Ebu Muslim deserves our admiration, who in an astonishingly short space of time gained over to his side all the Turks of Transoxiana, and attached them to himself to such a degree that the myths which even now live in the mouths of the Ozbegs and Turcomans compare him to the Caliph Alī for valour and wondrous works. At all events the influential individuality of Ebu Muslim first made the warlike supremacy of the Turks, although only mediately, felt in Western Asia.”