Abū Jaʿfar Abdullāh al-Maʾmūn ibn Harūn (also spelled Almamon, Al-Maymun, Al-Ma’moon,and el-Mâmoûn (Arabic: ابوجعفر عبدالله المأمون, Persian: ابوجعفر عبدالله مامون) ( 15 September 786 – 9 August 833) was an Abbasid caliph who reigned from 813 until his death in 833. He succeeded his brother al-Amin who was killed during the siege of Baghdad (813)
In 802 Harun al-Rashid, father of al-Maʾmūn and al-Amin, ordered that al-Amin succeed him, and al-Ma’mun serve as governor of Khurasan and as caliph after the death of al-Amin. In the last days of Harun’s life his health was declining and saw in a dream Musa ibn Jafar sitting in a chamber praying and crying, which made Harun remember how hard he had struggled to establish his own caliphate. He knew the personalities of both his sons and decided that for the good of the Abbasid dynasty, al-Maʾmūn should be caliph after his death, which he confided to a group of his courtiers. One of the courtiers, Fadl ibn Rabi’ did not abide by Harun’s last wishes and convinced many in the lands of Islam that Harun’s wishes had not changed. Later the other three courtiers of Harun who had sworn loyalty to Harun by supporting al-Maʾmūn, namely ‘Isa Jarudi, Abu Yunus, and Ibn Abi ‘Umran found loopholes in Fadl’s arguments, and Fazl admitted Harun had appointed al-Maʾmūn after him, but, he argued, since Harun was not in his right mind, his decision should not be acted upon. Al-Maʾmūn was reportedly the older of the two brothers, but his mother was a Persian woman while al-Amin’s mother was a member of the reigning Abbasid family. After al-Rashid’s death in 809, the relationship between the two brothers deteriorated. In response to al-Ma’mun’s moves toward independence, al-Amin declared his own son Musa to be his heir. This violation of al-Rashid’s testament led to a succession struggle. al-Amin assembled a massive army at Baghdad with ‘Isa ibn Mahan at its head in 811 and invaded Khorasan, but al-Maʾmūn’s general Tahir ibn al-Husayn (d. 822) destroyed the army and invaded Iraq, laying siege to Baghdad in 812. In 813 Baghdad fell, al-Amin was beheaded, and al-Maʾmūn became the undisputed Caliph.
Death
Al-Tabari (v.32, pp. 224–231) recounts how Al-Ma’mun was sitting on the river bank telling those with him how splendid the water was. He asked what would go best with this water and was told a specific kind of fresh dates. Noticing supplies arriving, he asked someone to check whether such dates were included. As they were, he invited those with him to enjoy the water with these dates. All who did this fell ill. Others recovered, but Al-Ma’mun died. He encouraged his successor to continue his policies and not burden the people with more than they could bear. This was on 9 August 833.
Al-Ma’mun died near Tarsus. The city’s major mosque (Tarsus Grand Mosque), contains a tomb reported to be his. He was succeeded not by his son, Al-Abbas ibn al-Ma’mun, but by his half-brother, al-Mu’tasim.
August 9,833 – death-Al-Ma'mun, Iraqi caliph (b. 786)