Al-Ma'mun

Abū al-ʿAbbās Abd Allāh ibn Hārūn al-Maʾmūn (; 14 September 786 – 9 August 833), better known by his regnal name '''al-Ma'mun''' (), was the seventh Abbasid caliph, who reigned from 813 until his death in 833. His leadership was marked by the power and prosperity of the Abbasid Caliphate, al-Ma'mun promoted the Graeco-Arabic translation movement, the flowering of learning and the sciences in Baghdad, and the publishing of al-Khwarizmi's book now known as "Algebra", making him one of the most important caliphs in the Islamic Golden Age. He is also known as a proponent of the rational Islamic theology of Mu'tazilism.

Al-Ma'mun succeeded his half-brother al-Amin after a civil war, much of his reign was spent on peace campaigns. His strong support for Mu'tazilism led him to imprison a Sunni Imam, Ahmad ibn Hanbal in an event that became known as ''mihna.'' Al-Ma'mun's foreign policy was due to his decision to continue war and diplomatic relations with the Byzantine Empire, the tension between conflict or diplomacy varying during his military campaigns. Provided by Wikipedia