The action of a “client” population of this sort was fraught with far greater consequences when another Koreishite family--the Abbasids, descendants of an uncle of Mohammed--rose up against the Omayyads. One of their great emissaries placed himself at the head of the Moslem natives of eastern Persia (Khorasan) and by the help of these Iranians the Abbasids secured the throne (750). The change must be regarded as in great measure a strong reaction of the Persian element against the Arab. The long succession of great oriental empires had been interrupted by an empire purely Arab, and the sequence was now renewed. The seat of government was once more transferred to Babylonia; Baghdad took the place of Babylon and Ctesiphon. The great offices of state were already largely filled by persons of other than Arab descent. The old Arab pride of birth was outraged by the fact that no weight was now attached to the consideration of whether the mother of the ruler had been a free woman or a slave, and that thus the Arab strain of the reigning dynasty became more and more interfused with foreign blood as time went on. A second Persian reaction is signalised by the victory won, after a protracted struggle, by the caliph Mamun, the son of a Persian woman, over his brother Amin, whose mother was of the stock of the Abbasids (813). Mamun’s troops were nearly all of them Persians. Their leader, the Persian Tahir, founded the first semi-independent sovereignty on Iranian soil. The forms of government remained Arab to a great extent, and Arabic likewise remained the official language, but genuine Arabdom receded more and more into the background. Above all, professional troops recruited from the peoples of the East, or even of the far West, had almost wholly superseded the Arab levies.