Excerpts from Books and Wikipedia
"The conquest of Baghdad by the Buwayhids of Persia in 945 finally ended the Abbasids' territorial power but, because of its residual prestige, they retained the caliphate as a purely spiritual office. Despite this, the Shi'ite Buwayhids treated the Sunni caliphs with undisguised contempt and forced them to celebrate Shi'ite festivals." By 1000, Cairo, Cordoba, and Ghazni had become the centers of Islamic culture. The Seljuk Turks were central Asian nomads who had converted to Sunni Islam around 1000. In 1054 their leader, Toghril Beg, were summoned by the caliph to recapture Baghdad from the Buyids. In 1055, Toghril Beg was welcomed into Baghdad by the caliph as a liberator. "The Turks emerged from this event as major players in the Muslim world." [Furtado: 1001 Days]