Abbasid authority in Syria and Iraq eroded considerably after the beginning of the "Anarchy at Samarra" in 861, which left the vast expanse of the Syrian and Arabian deserts without governmental oversight. During this period, the Tayy dominated the southern part of the Syrian Desert, the Banu Kilab dominated the northern part and the Banu Kalb dominated central Syria. The latter tribe, whose presence in the region had preceded the Muslim conquest and the migration of the Tayy and Kilab, was largely sedentarized, while the Tayy and Kilab, being relative newcomers to the region, were still highly mobile nomadic groups. According to Kamal Salibi, the Tayy's "chief military asset, in fact, was their Bedouin swiftness of movement". Moreover, the durable connections the Tayy of Syria maintained with their north Arabian counterparts in Jabal Tayy made them virtually independent and prone to revolt against the various Muslim states in Syria and Iraq.