Abu `Aun having provoked the Caliph’s wrath was dismissed from his office, and succeeded by Mu`āz ibn Muslim. A.H. 161 (777). The revolt of Mokanna`, “the Veiled Prophet of Khorāsān,” originated in a village near Merv. He taught the transmigration of souls, and gave out that the Deity had lately been incarnate in the person of Abū Muslim, and had now passed into his own. He secured a great following from among the people of Khorāsān and Transoxiana, who, from the colour of their clothes, took the name of _Sefīd-Jāmegān_, or the “White-robed.” A.H. 163 (779). Mokanna` was besieged by Sayyid el-Harashī in his fortress in Kesh, and on finding his position hopeless poisoned himself. His head was sent to El-Mahdi in Aleppo.[198] Mu`āz was supplanted by Musayyah ibn Zobayr in the governorship. A.H. 166 (782). A general rising took place against Musayyah, who was superseded by El-Fadhl ibn Sulaymān Tūsī in the governorships of Khorāsān and Sīstān. A.H. 167 (783). Death of El-Mahdi. Succession of El-Hādi. A.H. 170 (786). Death of El-Hādi. Succession of Hārūn er-Rashīd. A.H. 171 (787). Ja`far el-Ash`ath, governor of Khorāsān. A.H. 172 (788). El-`Abbās el-Ash`ath followed his father as governor, and was, A.H. 175 (791), succeeded by his uncle El-Ghatrīf ibn `Atā. A.H. 176 (792). Shi`ite revolt in Daylam. Hamza el-Khuzā`ī, governor of Khorāsān. A.H. 178 (794). El-Fadhl ibn Yahya was appointed governor of Khorāsān. A.H. 178 (794). He built mosques and post-stations in Khorāsān, conducted a “Holy War” in Transoxiana, and was unsuccessfully attacked by the king of Oshrūsana Khārakhara.[199] A.H. 179 (795). Mansūr el-Himyari was governor of Khorasan. A.H. 180 (796). Ja`far ibn Yahya was governor of Khorāsān and Sīstān. A.H. 182 (798). The famous Caliph Hārūn er-Rashīd appointed his infant son Ma´mūn ruler over all the countries from Hamadān to the farthest East, under the guardianship of Ja`far ibn Yahya. The year A.H. 187 (802) was memorable in Mohammedan annals for the sudden disgrace and fall of the all-powerful favourites of the Caliph, the Barmecides,[200] at that time represented by the brothers Fadhl and Ja`far and their aged father Yahya. Their story has been told too often to bear repetition in this place, although, as we have seen, the Barmecides had from their origin been closely connected with Khorāsān.