 "Early Middle Ages"

Upon Al-Amin's death, Al-Ma'mun became Caliph.Al-Ma'mun extended the Abbasid empire's territory during his reign and dealt with rebellions.Al-Ma'mun had been named governor of Khurasan by Harun, and after his ascension to power, the caliph named Tahir as governor of his military services in order to assure his loyalty.