Ma´mūn, who was now the undisputed master of the Caliphate, made Merv his capital instead of removing to Baghdād. He took this fatal step, which gave offence to the people of the West generally, on the advice of Fadhl ibn Sahl; for Ma´mūn, like his brother, was overruled by a selfish and masterful vezīr. After the capture of Baghdād, Tāhir placed himself at the head of affairs in that town; but the people soon rose against him to avenge the death of Amīn. The revolt was quelled by the distribution of largesses, and all `Irāk acknowledged Tāhir’s sway.[207] It is impossible to enumerate the disorders which distracted Baghdād and the West, and the countless difficulties which Ma´mūn had to face during the next few years. Suffice it to say that, in spite of repeated risings and conspiracies against the Caliph’s authority, Ma´mūn continued to be guided by the short-sighted counsels of his vezīr, who, as a Persian[208] and a Shī`ite, was hated in the orthodox West. Not till A.H. 202 (817) did the monarch awaken to the dangers of the situation and set out from Merv to Baghdād. On reaching Sarakhs, Fadhl, the real cause of all Ma´mūn’s misfortunes, was murdered in his bath--it appears, at the instigation of his master. In A.H. 204 (817) Ma´mūn entered Baghdād, and Tāhir, who had during the recent troubles fallen into disfavour with the Caliph, was now appointed governor of Baghdād. He did not remain long in this office, for at his own request he was appointed to the viceroyalty of the East, A.H. 205 (818).[209] With him the Caliph sent a confidential eunuch, who had orders to poison Tāhir should he show any signs of insubordination. After a successful rule of two years Tāhir suddenly omitted the Caliph’s name in the weekly prayers, and on the following day he was found dead in his bed, A.H. 207 (822). But so great were the esteem and influence which the viceroy had gained in Khorāsān, that the Caliph did not dare to take the governorship of that province out of the hands of Tāhir’s family. His two sons, Talha and `Abdullah, did not inherit his turbulent character; and whilst `Abdullah was fighting Ma´mūn’s battles in Mesopotamia and Egypt, his brother Talha governed the Eastern provinces (from A.H. 207–213 (822–828)) in the Caliph’s name. His residence was Nīshāpūr, whence he exercised complete authority over Khorāsān, Tabaristān, and Transoxiana. It is fitting in this place to revert to the rise of a family destined to play an important part in the East under the Tāhirides, and, after succeeding their former masters in the governorship of Khorāsān, to found the first independent Mohammedan dynasty in Central Asia.