Mamun, Abu Al-Abbas Abd Allah Al-
Mamun, Abu Al-Abbas Abd Allah Al-
Born September 786; died August 833. Caliph of the Abbasid dynasty (ruled 813-833). Son of Harun al-Rashid, he was governor in Khorasan from 809 to 813. Al-Mamun was known as a patron of learning and a supporter of the Muslim doctrines of the Mutazilites. He ruthlessly crushed popular uprisings in the Abbasid caliphate and launched wars of aggression against Byzantium.