An ethnic group originally from somewhere north of China (perhaps western Manchuria), which subsequently spread through migration and conquest across the steppes into Central Asia; by the 800s many served as servants within the Umayyad caliphate, and by the 900s many were soldiers or even generals under the Abbasids and its successor states--before eventually taking over much of the Asian portion of the Islamic world (perhaps in the process saving Sunni Islam as the dominant branch of the faith)