Abu Jafar al-Ma'mun ibn Harun (also spelled Almamon and el-Mâmoûn) (September 14, 786 – August 9, 833) (المأمون) was an Abbasid caliph who reigned from 813 until his death in 833. He succeeded his brother al-Amin.
There were disturbances in Iraq during the first several years of al-Ma'mun's reign, while the caliph was in Merv. On November 13, 815 Muhammad Jafar claimed the Caliphate for himself in Mecca. He was defeated and he quickly abdicated asserting that he'd only become caliph on news that al-Ma'mun had died. Lawlessness in Baghdad led to the formation of neighborhood watches. When in A.H. 201 (817 CE) al-Ma'mun named Imam Reza the Seventh descendent of Muhammad his heir, this was not accepted by people in Baghdad. This was a political move by al-Ma'mun since most of Persia was sympathetic to the Hashemites. Al-Ma'mun's opponents in Baghdad gave allegiance to Ibrahim ibn al-Mahdi. His forces fought Kharijites, al-Ma'mun's and arrested the neighbourhood watch commander Sahl ibn Salamah.
Imam Reza informed al-Ma'mun of happenings in Baghdad and al-Ma'mun set out for the City of Peace on the day the fast ended, April 12, 818. At Tus he stopped to visit his father's grave. On the last day of Safar in 203 AH, al-Ma'mun poisoned Imam Reza through grapes in Toos. Imam Reza was buried beside the caliph's grave. Following the death of Imam Reza a great revolt took place in Khurasan, Persia. Al-Ma’mun wept and mourn for Imam Reza and tried to show himself innocent of the crime. But for all he did, he could not get himself acquitted and prove his innocence. Al-Ma'mun wrote to Hasan ibn Sahl, his governor in Iraq, the Hijaz, etc. informing him of his grief on the Imam's death. The governor fell ill and al-Ma'mun appointed Dinar ibn Abdallah to replace him. Some of Ibn al-Mahdi's commanders deserted him, and he died.
Also in 210 there was an uprising in Qum sparked by complaints about taxes. After it was quashed, the tax assessment was set significantly higher. In 212 there was an uprising in Yemen. In 214 (829-830) Abu al-Razi who had captured one Yemeni rebel was killed by another. Egypt continued to be unquiet. Sind was rebellious. In 216 (831-832) Ghassan ibn Abbad subdued it. An ongoing problem for al-Ma'mun was the uprising headed by Babak Khorramdin. In 214 Babak routed a Caliphate army killing its commander Muhammad ibn Humayd.
There was also struggle against the Byzantines. In 215 (830) al-Ma'mun led a victorious force across the border. He captured several fortresses, sparing the surrendering Byzantines. The next year, learning Byzantines had killed some sixteen hundred people, he returned. This time some thirty forts fell to the Caliphate forces. The following year Byzantium's Theophilus wrote to al-Ma'mun. The caliph replied that he carefully considered the Byzantine ruler's letter, noticed it blended suggestions of peace and trade with threats of war and offered Theophilus the options of acknowledging divine unity, paying tax or fighting. Al-Ma'mun made preparations for a major campaign and died on the way.
In 829, Michael II died and was succeeded by his son Theophilos. Theophilos received a mixed diet of success and defeat against his Arab opponents. In 830 CE the Arabs returned to Sicily and after a year-long siege took Palermo from their Christian opponents and for the next 200 years they were to remain there to complete their conquest, which was never short of Christian counters.The Caliph Al-Ma'mun meanwhile launched an invasion of Anatolia in 830 CE. Al-Ma'mun triumphed and a number of Byzantine forts were lost he spared the surrendering Byzantines. Theophilos did not relent and in 831 captured Tarsus from the Muslims.The next year, learning Byzantines had killed some sixteen hundred people, Al-Ma'mun returned. This time some thirty forts fell to the Caliphate forces, with two Byzantine defeats in Cappadocia. This would be followed by the destruction of Melitene, Samosata and Zapetra by the vengeful Byzantine troops in 837 CE.
Theophilos wrote to Al-Ma'mun. The Caliph replied that he carefully considered the Byzantine ruler's letter, noticed it blended suggestions of peace and trade with threats of war and offered Theophilos the options of acknowledging divine unity, paying tax or fighting. Al-Ma'mun made preparations for a major campaign and died on the way while leading an expedition in Sardis.
Al-Ma'mun's relations with the Byzantine Romans is marked by his efforts in the translation of Greek philosophy and science. Al-Ma'mun gathered scholars of many religions at Baghdad, whom he treated magnificently and with tolerance. He sent an emissary to the Byzantine Empire to collect the most famous manuscripts there, and had them translated into Arabic. It is said that, victorious over the Byzantine Emperor, Al-Ma'mun made a condition of peace be that the emperor hand over of a copy of the "Almagest".
Al-Ma'mun's record as an administrator is also marked by his efforts toward the centralization of power and the certainty of succession. The Bayt al-Hikma, or House of Wisdom, was established during his reign. The ulema emerged as a real force in Islamic politics during al-Ma'mun's reign for opposing the mihna, which was instituted in 827.
The mihna, or 'ordeal,' is comparable to Medieval European inquisitions only in the sense that it involved imprisonment, a religious test, and a loyalty oath. The casualties of Abbasid inquisition would not approach a fraction of those executed in Europe under similar circumstances. In the effort to centralize power and test the loyalty of his subjects, al-Ma'mun required elites, scholars, judges and other government officials to undergo the test, which was a series of questions relating to theology and faith. The penalty for failing the mihna could include death.
The controversy over the mihna was exacerbated by al-Ma'mun's sympathy for Mu'tazili theology and other controversial views. Mu'tazili theology was deeply influenced by Aristotelian thought and Greek rationalism, and stated that matters of belief and practice should be decided by reasoning on the basis of the Qur'an. This defied the literalist position of Ahmad ibn Hanbal and others, according to which everything a believer needed to know about faith and practice was spelled out literally in the Qur'an and the Hadith. Moreover, the Mu'tazilis stated that the Qur'an was created rather than eternal, a belief that was shared by the Jahmites and Shi'a, among others, but contradicted the Sunni opinion that the Qur'an and the Divine were coeternal. The fact that the Mu'tazili school had its foundations in the paganism of Greece further disenchanted a majority of Islamic clerics.
Although al-Mahdi had proclaimed that the caliph was the protector of Islam against heresy, and had also claimed the ability to declare orthodoxy, religious scholars in the Islamic world believed that al-Ma'mun was overstepping his bounds in the mihna. The penalties of the mihna became increasingly difficult to enforce as the ulema became firmer and more united in their opposition. Although the mihna persisted through the reigns of two more caliphs, al-Mutawakkil abandoned it in 848. The failure of the mihna seriously damaged Caliphal authority and ruined the reputation of the office for succeeding caliphs. The caliph would lose much of his religious authority to the opinion of the ulema as a result of the mihna.
The ulema and the major Islamic law schools became truly defined in the period of al-Ma'mun and Sunnism, as a religion of legalism, became defined in parallel. Doctrinal differences between Sunni and Shi'a Islam began to become more pronounced. Ibn Hanbal, the founder of the Hanbali legal school, became famous for his opposition to the mihna. Al-Ma'mun's simultaneous opposition and patronage of intellectuals led to the emergence of important dialogues on both secular and religious affairs, and the Bayt al-Hikma became an important center of translation for Greek and other ancient texts into Arabic. This Islamic renaissance spurred the rediscovery of Hellenism and ensured the survival of these texts into the European renaissance.
Al-Ma'mun had been named governor of Khurasan by Harun, and after his ascension to power, the caliph named Tahir as governor for his military services in order to assure his loyalty. It was a move that al-Ma'mun soon regretted, as Tahir and his family became entrenched in Iranian politics and became increasingly powerful in the state, contrary to al-Ma'mun's desire to centralize and strengthen Caliphal power. The rising power of the Tahirid dynasty became a threat as al-Ma'mun's own policies alienated them and his other opponents.
The shakiriya, which were to trigger the movement of the capital from Baghdad to Samarra during al-Mu'tasim's reign, were raised in al-Ma'mun's time. The shakiriya were military units from Central Asia and North Africa, hired, complete with their commanders, to serve under the Caliph.
Al-Ma'mun, in an attempt to win over the Shi'a Muslims to his camp, named the eighth Imam, Ali ar-Rida, his successor, if he should outlive al-Ma'mun. Most Shi'ites realized, however, that ar-Rida was too old to survive him and saw al-Ma'mun's gesture as empty; indeed, ar-Rida died in 818. The incident served to further alienate the Shi'ites from the Abbasids, who had already been promised and denied the Caliphate by al-'Abbas. Later Ma'mun, fearing an uprising, had Ali Ar-Rida poisoned.
Al-Ma'mun also attempted to divorce his wife during his reign, who had not borne him any children. His wife hired a Syrian judge of her own before al-Ma'mun was able to select one himself; the judge, who sympathized with the caliph's wife, refused the divorce. Following al-Ma'mun's experience, no further Abbasid caliphs were to marry, preferring to find their heirs in the harem.
The Abbasid empire grew somewhat during the reign of al-Ma'mun. Hindu rebellions in Sindh were put down, and most of Afghanistan was absorbed with the surrender of the leader of Kabul. Mountainous regions of Iran were brought under a tighter grip of the central Abbasid government, as were areas of Turkestan.
Shortly before his death, during a visit to Egypt in 832, the caliph ordered the breaching of the Great Pyramid of Giza looking for knowledge and treasure. He entered the pyramid by tunneling into the Great Pyramid near where tradition located the original entrance. (At this time the pyramid was covered with a smooth outer layer of casing stones. The Roman historian Strabo visited the pyramid in 24 BC and records that the entrance was hinged and indistinguishable from the surrounding casing stones.) Since the upper passages were blocked from access by a concealed granite plug until Al Mamun's forced entrance, it's probable that no one had been in the upper passages since the time of its construction. Debate regarding the reason for the construction of the Great Pyramid continues since no body was ever found.
Al-Ma'mun died near Tarsus and the city's major mosque contains a tomb reported to be his. He was succeeded by his half-brother, al-Mu'tasim.

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