The Umayyads who had put down the Kharijites in Asia had been compelled by the course of events to seek a refuge in Africa for themselves, and thence had passed over to Spain which was regarded as the remotest of the western parts. At this time they were ruling at Cordova (they did not assume the title of Khalif until A.H. 317), and held also some possessions in Africa about Oran. The same Karmati leader who had taken Tiharet was able to seize Oran. The Idrisid dynasty, descendants of ʿAli by Hasan, expelled from Madina in 169, had founded a state in the remoter part of Morocco where they were still ruling. This state also was attacked by Aruba and reduced, so that all the western lands to the Atlantic coast was brought under the control of the Mahdi (Ibn Khald. i. 244-5, 267-8, etc.). This course of consolidation of the most loosely held part of the Muslim world speaks well for the organising ability of the general Aruba, and established the Mahdi’s authority upon a sound foundation. It was, however, disturbed by domestic difficulties in the capital. Kairawan was an Arab colony, but under the Mahdi the Berbers were in the ascendant, and racial disputes were inevitable. One day a Katama tribesman treated a city merchant with insolence; a riot ensued, and some 1,000 of the Katama were slain. After this had been repressed the governor rode through the city and ordered the dead bodies of the Berbers to be removed. The workmen who carried out this order threw the bodies into the channel which served as the city sewer. At this the Katama tribesmen removed from the city in indignation, and declared that they would no longer submit to the Mahdi’s rule, and chose a youth named Kadu as their emir. Very soon this rebel was in possession of the whole province of Zab, and the Mahdi sent several generals against him without result. Some of these generals, indeed, deserted to the enemy, for the Berbers were the main fighting force in Africa, and there was a general indignation amongst them at the way in which the Katama rebels in Kairawan had been treated, and there were many followers of Abu ʿAbdullah still who threw in their lot with the revolted Berbers. At length ʿUbayd Allah sent his son Abu l-Qasim, and he, with some difficulty, managed to reduce the tribesmen.