Seljuk Turks, a group of Islamic nomadic peoples, lived mostly on the borders of the Abbasid empire. By the mid- to late tenth century, great numbers of Seljuk Turks served in the Abbasid armies and lived in the actual empire.
After gradually "encroaching in" on their society, in 1055, the Abbasid caliph recognized the Seljuq leader Tughril Beg as sultan (“chieftain” or “ruler”). Tughril Beg and his successors eventually extended Turkish rule to Syria, Palestine, and other parts of the Abbasid empire.
For the last 2 centuries of the Abbasid state, the caliphs served as figureheads while actual authority lay in the hands of Turkish sultans
While some Turkish peoples established themselves in Abbasid Persia, others turned towards the Byzantine empire and Anatolia
Led by the Seljuqs, Turkish peoples began migrating into Anatolia in the early 11th century. In 1071, Seljuq forces defeated the Byzantines at Manzikert in eastern Anatolia and displaced Byzantine authorities and set up their own political and social institutions.
They levied taxes on the Byzantine church, restricted its activities, and sometimes confiscated church property. They welcomed converts to Islam and made political, social, and economic opportunities available to the converts.
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