New Groups. When the Abbasid khilafah was founded in 750, it governed a strong, centralized state with the khalifah as an effective ruler, soon installed in the newly built capital of Baghdad. Gradually the centralized khilafah began to lose its effectiveness, and regional powers began to appear, leading to the decentralization of the khilafah and, in later years, to its fragmentation into autonomous units. By the middle of the tenth century the Arabs, who had been the dominant, ruling elite, began to recede in importance. Iranians, as well as Kurdish and Turkish military groups who had converted to Islam, began to wield more power. The khalifahs lost their authority and effectiveness and became symbolic figureheads who lent the ummah a semblance of unity even as the centralized government continued to break up. The real rulers, military commanders who were...