Editing Al-Mu'tasim (section)

== Caliphate ==
[[Al-Ma'mun]] had made no official provisions for his succession. His son, al-Abbas, was old enough to rule and had acquired experience of command in the border wars with the Byzantines, but had not been named heir.{{sfn|Kennedy|2006|p=213}} According to the account of al-Tabari, on his deathbed al-Ma'mun dictated a letter nominating his brother, rather than al-Abbas, as his successor,{{sfn|Bosworth|1987|pp=222–223, 225}} and Abu Ishaq was acclaimed as caliph on 9{{spaces}}August, with the [[regnal name]] of al-Mu'tasim (in full ''al-Muʿtaṣim bi’llāh'', "he who seeks refuge in God").{{sfn|Bosworth|1991|p=1}} It is impossible to know whether this reflects actual events, or whether the letter was an invention and Abu Ishaq merely took advantage of his proximity to his dying brother, and al-Abbas's absence, to propel himself to the throne. As Abu Ishaq was the forefather of all subsequent Abbasid caliphs, later historians had little desire to question the legitimacy of his accession, but it is clear that his position was far from secure: a large part of the army favoured al-Abbas, and a delegation of soldiers even went to him and tried to proclaim him as the new Caliph. Only when al-Abbas refused them, whether out of weakness or out of a desire to avoid a civil war, and himself took the oath of allegiance to his uncle, did the soldiers acquiesce in al-Mu'tasim's succession.{{sfn|Kennedy|2006|pp=213–215}}{{sfn|Bosworth|1991|pp=1–2 (esp. note 2)}} The precariousness of his position is further evidenced by the fact that al-Mu'tasim immediately called off the expedition, abandoned the Tyana project and returned with his army to Baghdad, which he reached on 20{{spaces}}September.{{sfn|Kennedy|2006|pp=215–216}}{{sfn|Treadgold|1988|p=281}}{{sfn|Bosworth|1991|p=2}}

=== New elites and administration ===
[[File:Dirham of al-Mu'tasim, AH 221.jpg|thumb|upright=1.2|alt=Obverse and reverse of silver coin with Arabic inscriptions|Silver ''[[dirham]]'' of al-Mu'tasim, minted at [[al-Muhammadiya]] in 836/7]]
Whatever the true background of his accession, al-Mu'tasim owed his rise to the throne not only to his strong personality and leadership skills, but principally to the fact that he was the only Abbasid prince to control independent military power, in the form of his Turkish corps.{{sfn|Kennedy|2004a|pp=156–157}} Unlike his brother, who tried to use the tribal Arabs and the Turks to balance out the Iranian troops, al-Mu'tasim relied almost exclusively on his Turks; the historian Tayeb El-Hibri describes al-Mu'tasim's regime as "militaristic and centred on the Turkish corps".{{sfn|El-Hibri|2010|p=296}} The rise of al-Mu'tasim to the caliphate thus heralded a radical change in the nature of Abbasid administration, and the most profound shift the Islamic world had experienced since the dynasty had come to power in the [[Abbasid Revolution]]. While the latter had been backed by a mass popular movement seeking to enact social reforms, al-Mu'tasim's revolution was essentially the project of a small ruling elite aiming to secure its own power.{{sfn|Kennedy|2004a|pp=155, 156}}

Already under al-Ma'mun, old-established Arab families such as the [[Muhallabids]] disappeared from the court, and minor members of the Abbasid family ceased to be appointed to governorships or senior military positions.{{sfn|Kennedy|2004a|p=155}} The reforms of al-Mu'tasim completed this process, resulting in the eclipse of the previous Arab and Iranian elites, both in Baghdad and the provinces, in favour of the Turkish military, and an increasing centralization of administration around the caliphal court. A characteristic example is Egypt, where the Arab settler families still nominally formed the country's garrison (''[[jund]]'') and thus continued to receive a salary from the local revenues. Al-Mu'tasim discontinued the practice, removing the Arab families from the army registers (''[[divan|diwān]]'') and ordering that the revenues of Egypt be sent to the central government, which would then pay a cash salary (''ʿaṭāʾ'') only to the Turkish troops stationed in the province.{{sfn|Kennedy|2004a|pp=158–159}} Another departure from previous practice was al-Mu'tasim's appointment of his senior lieutenants, such as Ashinas and Itakh, as nominal super-governors over several provinces. This measure was probably intended to allow his chief followers immediate access to funds with which to pay their troops, but also, according to Kennedy, "represented a further centralizing of power, for the under-governors of the provinces seldom appeared at court and played little part in the making of political decisions".{{sfn|Kennedy|2004a|p=159}} Indeed, al-Mu'tasim's caliphate marks the apogee of the central government's authority, in particular as expressed in its right and power to extract taxes from the provinces, an issue that had been controversial and had faced much local opposition since the early days of the Islamic state.{{sfn|Kennedy|2004a|p=159}}

The one major exception to this process were the Tahirids, who remained in place as autonomous governors of their Khurasani super-province, encompassing most of the eastern Caliphate. The Tahirids provided the governor of Baghdad, and helped to keep the city, a focus of opposition under al-Ma'mun, quiescent. The post was held throughout al-Mu'tasim's reign by Abdallah ibn Tahir's cousin [[Ishaq ibn Ibrahim al-Mus'abi|Ishaq ibn Ibrahim ibn Mus'ab]], who, according to the Orientalist [[C. E. Bosworth]], was "always one of al-Mu'tasim's closest advisers and confidants".{{sfn|Bosworth|1993|p=776}}{{sfn|Kennedy|2004a|pp=159–160}} Apart from the Turkish military and the Tahirids, al-Mu'tasim's administration depended on the central fiscal bureaucracy. As the main source of revenue was the rich lands of southern Iraq (the [[Sawad]]) and neighbouring areas, the administration was staffed mostly with men drawn from these regions. The new caliphal bureaucratic class that emerged under al-Mu'tasim was thus mostly Persian or [[Aramaeans|Aramean]] in origin, with a large proportion of newly converted Muslims and even a few [[Nestorian Christians]], who came from landowner or merchant families.{{sfn|Kennedy|2004a|pp=160–161}}

On his accession, al-Mu'tasim appointed as his chief minister or [[Vizier (Abbasid Caliphate)|vizier]] his old personal secretary, [[al-Fadl ibn Marwan]]. A man trained in the traditions of the Abbasid bureaucracy, he was distinguished for his caution and frugality, and tried to shore up the finances of the state. These traits eventually caused his downfall, when he refused to authorize the Caliph's gifts to his courtiers on the grounds that the treasury could not afford it. He was dismissed in 836, and was lucky not to suffer any punishment more severe than being sent into exile to the village of al-Sinn.{{sfn|Bosworth|1991|pp=28–35}}{{sfn|Kennedy|2006|pp=216–217}} His replacement, [[Muhammad ibn al-Zayyat]], was of a completely different character: a rich merchant, he is described by Kennedy as "a competent financial expert but a callous and brutal man who made many enemies", even among his fellow members of the administration. Nevertheless, and even though his political authority never extended beyond the fiscal domain, he managed to maintain his office to the end of the reign, and under al-Mu'tasim's successor, [[al-Wathiq]] ({{reign|842|847}}), as well.{{sfn|Bosworth|1993|p=776}}{{sfn|Kennedy|2004a|p=161}}

=== Rise of the Turks ===
Al-Mu'tasim's reliance on his Turkish ''ghilmān'' grew over time, especially in the aftermath of an abortive plot against him discovered in 838, during the Amorium campaign. Headed by [['Ujayf ibn 'Anbasa|Ujayf ibn Anbasa]], a long-serving Khurasani who had followed al-Ma'mun since the civil war against [[al-Amin]], the conspiracy rallied the traditional Abbasid elites, dissatisfied with al-Mu'tasim's policies and especially his favouritism towards the Turks. Discontent with the latter grew due to their servile origin, which offended the Abbasid aristocracy.{{efn|The sullen and rebellious mood of the ''abnāʾ'' and the Iranian elements of the Abbasid elite is conveyed by al-Tabari, who reports two of the leading conspirators, [[Amr al-Farghani]] and [[Ahmad ibn al-Khalil ibn Hisham]], grumbling during the siege of Amorium about being humbled by Ashinas, "this slave, the son of a whore", and that they would rather defect to the Byzantines than continue to serve under him.{{sfn|Bosworth|1991|p=112}}}} The plotters aimed to kill the Caliph and raise al-Ma'mun's son al-Abbas in his stead. According to al-Tabari, al-Abbas, although privy to these designs, rejected Ujayf's urgent suggestions to kill al-Mu'tasim during the initial stages of the campaign for fear of appearing to undermine the [[jihad]]. In the event, Ashinas grew suspicious of al-Farhgani and Ibn Hisham, and the plot was soon uncovered. Al-Abbas was imprisoned, and the Turkish leaders Ashinas, Itakh, and [[Bugha the Elder]] undertook to discover and arrest the other conspirators. The affair was the signal for a large-scale purge of the army that Kennedy describes as "of almost [[Stalin]]esque ruthlessness". Al-Abbas was forced to die of thirst, while his male offspring were arrested, and likely executed, by Itakh. The other leaders of the conspiracy were likewise executed in ingeniously cruel ways, which were widely publicized as a deterrent to others. According to the ''[[Kitab al-'Uyun]]'', about seventy commanders and soldiers were executed, including some Turks.{{sfn|Bosworth|1991|pp=xv, 121–134}}{{sfn|Gordon|2001|pp=48–49, 76–77}}{{sfn|Kennedy|2006|pp=224–227}}

As the historian Matthew Gordon points out, these events are probably connected to the disappearance of the ''abnāʾ'' from the historical record. Correspondingly they must have increased the standing of the Turks and their chief commanders, particularly Ashinas: in 839, his daughter, Utranja, married the son of al-Afshin, and in 840, al-Mu'tasim appointed him as his deputy during his absence from Samarra. When he returned, al-Mu'tasim publicly placed him on a throne and awarded him a ceremonial crown.{{sfn|Gordon|2001|p=77}}{{sfn|Bosworth|1991|p=178}} In the same year, Ashinas was appointed to a super-governorate over the provinces of Egypt, Syria and the Jazira. Ashinas did not govern these directly, but appointed deputies as governors, while he remained in Samarra.{{sfn|Gordon|2001|p=77}}{{sfn|Bosworth|1991|p=178 (note 504)}} When Ashinas participated in the Hajj of 841, he received honours on every stop of the route.{{sfn|Gordon|2001|p=77}}{{sfn|Bosworth|1991|p=201}} In 840, it was the turn of al-Afshin to fall victim to the Caliph's suspicions. Despite his distinguished service as a general, he was very much the "odd man out" in the Samarran elite; the relations of the Iranian prince with the low-born Turkish generals were marked by mutual antipathy. Furthermore, he alienated the Tahirids, who might under other circumstances have been his natural allies, by interfering in [[Tabaristan]], where he allegedly encouraged the local autonomous ruler, [[Mazyar]], to reject Tahirid control (see [[#Mazyar|below]]).{{sfn|Kennedy|2006|p=227}} Al-Tabari reports other allegations against al-Afshin: that he was plotting to poison al-Mu'tasim; or that he was planning to escape to his native Ushrusana with vast sums of money.{{sfn|Bosworth|1991|pp=180–185}} According to Kennedy, the very variety of allegations against al-Afshin is grounds for skepticism about their truthfulness, and it is likely that he was framed by his enemies at court.{{sfn|Kennedy|2006|p=227}} Whatever the truth, these allegations discredited al-Afshin in the eyes of al-Mu'tasim. He was dismissed from his position in the caliphal bodyguard (''al-ḥaras''),{{sfn|Bosworth|1991|p=179}} and a [[show trial]] was held at the palace, where he was confronted with several witnesses, including Mazyar. Al-Afshin was accused, among other things, of being a false Muslim, and of being accorded [[Shirk (Islam)|divine status]] by his subjects in Ushrusana. Despite putting up an able and eloquent defence, al-Afshin was found guilty and thrown into prison. He died soon after, either of starvation or of poison. His body was publicly [[gibbet]]ed in front of the palace gates, burned, and thrown in the Tigris.{{sfn|Bosworth|1991|pp=185–193}}{{sfn|Kennedy|2006|pp=227–229}} Once more, the affair enhanced the standing of the Turkish leadership, and particularly [[Wasif al-Turki|Wasif]], who now received al-Afshin's revenues and possessions.{{sfn|Gordon|2001|pp=77–78}}

Nevertheless, it seems that al-Mu'tasim was not entirely satisfied with the men he had raised to power. An anecdote dating from his last years, relayed by Ishaq ibn Ibrahim ibn Mus'ab, recalls how the Caliph, in an intimate exchange with Ishaq, lamented that he had made poor choices in this regard: while his brother al-Ma'mun had nurtured four excellent servants from the Tahirids, he had raised al-Afshin, who was dead; Ashinas, "a feeble heart and a coward"; Itakh, "who is totally insignificant"; and Wasif, "an unprofitable servant". Ishaq himself then suggested that this was because, while al-Ma'mun had used men with local connections and influence, al-Mu'tasim had used men with no roots in the Muslim community, to which the Caliph sadly assented.{{sfn|Bosworth|1991|pp=212–215}}{{sfn|Kennedy|2006|pp=230–231}}

=== Foundation of Samarra ===
[[File:Abbasid Samarra Map.svg|thumb|right|upright=0.8|alt=Topographic map showing the course of the Tigris river in blue and the settled areas of the city in orange, with their names|Map of [[Abbasid Samarra]]]]
The Turkish army was at first quartered in Baghdad, but quickly came into conflict with the remnants of the old Abbasid establishment in the city and the city's populace. The latter resented their loss of influence and career opportunities to the foreign troops, who were furthermore often undisciplined and violent, spoke no Arabic, and were either recent converts to Islam or still pagans. Violent episodes between the populace and the Turks thus became common.{{sfn|Kennedy|2006|pp=218–219}}

This was a major factor in al-Mu'tasim's decision in 836 to found a new capital at [[Abbasid Samarra|Samarra]], some {{convert|80|mi|km}} north of Baghdad, but there were other considerations in play. Founding a new capital was a public statement of the establishment of a new regime. According to Tayeb El-Hibri it allowed the court to exist "at a distance from the populace of Baghdad and protected by a new guard of foreign troops, and amid a new royal culture revolving around sprawling palatial grounds, public spectacle and a seemingly ceaseless quest for leisurely indulgence", an arrangement compared by [[Oleg Grabar]] to the relationship between [[Paris]] and [[Palace of Versailles|Versailles]] after [[Louis XIV]].{{sfn|Kennedy|2004a|p=163}}{{sfn|El-Hibri|2010|pp=296–297}} By creating a new city in a previously uninhabited area, al-Mu'tasim could reward his followers with land and commercial opportunities without cost to himself and free from any constraints, unlike Baghdad with its established interest groups and high property prices. In fact, the sale of land seems to have produced considerable profit for the treasury—in the words of Kennedy, "a sort of gigantic property speculation in which both government and its followers could expect to benefit".{{sfn|Kennedy|2004a|p=163}}

Space and life in the new capital were strictly regimented: residential areas were separated from the markets, and the military was given its own cantonments, separated from the ordinary populace and each the home of a specific ethnic contingent of the army (such as the Turks or the [[Maghariba (Abbasid troops)|Maghariba]] regiment). The city was dominated by its mosques (most famous among which is the [[Great Mosque of Samarra]] built by Caliph [[al-Mutawakkil]] in 848–852) and palaces, built in grand style by both the caliphs and their senior commanders, who were given extensive properties to develop.{{sfn|Kennedy|2004a|p=163}}{{sfn|El-Hibri|2010|pp=297–298}} Unlike Baghdad, the new capital was an entirely artificial creation. Poorly sited in terms of water supply and river communications, its existence was determined solely by the presence of the caliphal court, and when the capital returned to Baghdad, sixty years later, Samarra was rapidly abandoned.{{sfn|Kennedy|2004a|pp=163–164}} Due to this, the ruins of the Abbasid capital are still extant, and the city can be mapped with great accuracy by modern archaeologists.{{sfn|Kennedy|2006|pp=219–220}}

=== Science and learning ===
As a military man, al-Mu'tasim's outlook was utilitarian, and his intellectual pursuits could not be compared with those of al-Ma'mun or his successor al-Wathiq, but he continued his brother's policy of promoting writers and scholars.{{sfn|Kennedy|2006|pp=215, 244}} Baghdad remained a [[Science in the medieval Islamic world|major centre of learning]] throughout his reign. Among the notable scholars active during his reign were the astronomers [[Habash al-Hasib al-Marwazi]]{{sfn|Sarton|1927|p=565}}{{sfn|Freely|2015|p=31}} and [[Ahmad al-Farghani]],{{sfn|Freely|2015|p=31}} the polymath [[al-Jahiz]],{{sfn|Freely|2015|p=52}} and the distinguished Arab mathematician and philosopher [[al-Kindi]], who dedicated his work ''On First Philosophy'' to his patron al-Mu'tasim.{{sfn|Freely|2015|pp=48–51}}{{sfn|Sarton|1927|p=559}} The Nestorian physician [[Salmawayh ibn Bunan]], a patron of the fellow Nestorian physician and [[Graeco-Arabic translation movement|translator]] [[Hunayn ibn Ishaq]], became court physician to al-Mu'tasim,{{sfn|Sarton|1927|pp=573–574}} while another prominent Nestorian physician, Salmawayh's rival [[Ibn Masawayh]], received apes for [[dissection]] from the caliph.{{sfn|Sarton|1927|p=574}} The physician [[Ali ibn Sahl Rabban al-Tabari|Ali al-Tabari]] was listed as being present in al-Mu'tasim's court, along with [[Masawaiyh|Ibn Masawayh]].<ref>{{Cite journal |last=Hamarneh |first=Sami |date=July 1972 |title=Pharmacy in medieval islam and the history of drug addiction |journal=Medical History |volume=16 |issue=3 |pages=226–237 |doi=10.1017/s0025727300017725 |pmc=1034978 |pmid=4595520}}</ref>

=== Mu'tazilism and the ''miḥna'' ===
[[File:Mihna Map.svg|thumb|right|upright=1.2|alt=Map of the Middle East with the main areas and events associated with the mihna labelled|Map of the events associated with the ''[[mihna|miḥna]]'' from 833 to 852]]
Ideologically, al-Mu'tasim followed the footsteps of al-Ma'mun, continuing his predecessor's support for [[Mu'tazilism]], a theological doctrine that attempted to tread a middle way between [[secular]] monarchy and the [[theocratic]] approach espoused by the Alids and the various sects of [[Shi'ism]]. Mu'tazilis espoused the view that the [[Quran]] was [[Quranic createdness|created]] and hence fell within the authority of a God-guided ''[[imam|imām]]'' to interpret according to the changing circumstances. While revering [[Ali]], they avoided taking a position on the righteousness of the opposing sides in the [[First Fitna|conflict]] between Ali and his opponents.{{sfn|Kennedy|2004a|pp=161–162}} Mu'tazilism was officially adopted by al-Ma'mun in 827, and in 833, shortly before his death, al-Ma'mun made its doctrines compulsory, with the establishment of an inquisition, the ''[[mihna|miḥna]]''. During his brother's reign, al-Mu'tasim played an active role in the enforcement of the ''miḥna'' in the western provinces; this continued after his accession. The chief advocate of Mu'tazilism, the head ''[[qadi|qādī]]'' [[Ahmad ibn Abi Duwad]], was perhaps the dominant influence at the caliphal court throughout al-Mu'tasim's reign.{{sfn|El-Hibri|2010|pp=291–292}}{{sfn|Bosworth|1991|p=xvi}}{{sfn|Kennedy|2004a|p=162}}

Thus Mu'tazilism became closely identified with the new regime of al-Mu'tasim. Adherence to Mu'tazilism was transformed into an intensely political issue, since to question it was to oppose the authority of the Caliph as the God-sanctioned ''imām''. While Mu'tazilism found broad support, it was also passionately opposed by traditionalists, who held that the Quran's authority was absolute and unalterable as the literal [[revelation|word of God]]. Opposition to Mu'tazilism also provided a vehicle for criticism by those who disliked the new regime and its elites.{{sfn|Kennedy|2004a|pp=162–163}} In the event, the active repression of the traditionalists was unsuccessful, and even proved counterproductive: the beating and imprisonment of one of the most resolute opponents of Mu'tazilism, [[Ahmad ibn Hanbal]], in 834, only helped to spread his fame. By the time al-Mutawakkil abandoned Mu'tazilism and returned to traditional orthodoxy in 848, the strict and conservative [[Hanbali]] school had emerged as the leading school of jurisprudence (''[[fiqh]]'') in [[Sunni Islam]].{{sfn|Bosworth|1991|p=xvi}}{{sfn|El-Hibri|2010|pp=293–295}}

=== Domestic campaigns ===
Although al-Mu'tasim's reign was a time of peace in the Caliphate's heartland territories, al-Mu'tasim himself was an energetic campaigner, and according to Kennedy "acquired the reputation of being one of the warrior-caliphs of Islam".{{sfn|Kennedy|2004a|p=164}} With the exception of the Amorium campaign, most of the military expeditions of al-Mu'tasim's reign were domestic, directed against rebels in areas that, although nominally part of the Caliphate, had remained outside effective Muslim rule and where native peoples and princes retained ''de facto'' autonomy.{{sfn|Kennedy|2004a|p=164}} The three great campaigns of the reign—Amorium, the expedition against the Khurramite rebellion, and that against Mazyar, ruler of Tabaristan—were in part also conscious propaganda exercises, in which al-Mu'tasim could solidify his regime's legitimacy in the eyes of the populace by leading wars against infidels.{{sfn|Kennedy|2006|p=220}}

An Alid revolt led by [[Muhammad ibn Qasim (al-Alawi)|Muhammad ibn Qasim]] broke out in Khurasan in early 834, but was swiftly defeated and Muhammad brought as a prisoner to the Caliph's court. He managed to escape during the night of 8/9{{spaces}}October 834, taking advantage of the [[Eid al-Fitr]] festivities, and was never heard of again.{{sfn|Bosworth|1991|pp=5–7}} In June/July of the same year, Ujayf ibn 'Anbasa was sent to subdue the [[Zutt]]. These were people who had been brought from [[India]] by the [[Sassanid]] emperors and settled in the [[Mesopotamian Marshes]]. The Zutt had been in rebellion against caliphal authority since {{circa|820}}, and had frequently raided the environs of [[Basra]] and [[Wasit]]. After a seven-month campaign, Ujayf was successful in encircling the Zutt and forcing them to surrender. He made a triumphal entry into Baghdad in January 835 with numerous captives. Many of the Zutt were then sent to [[Ayn Zarba]] on the Byzantine frontier, to fight against the Byzantines.{{sfn|Bosworth|1991|pp=7–12}}{{sfn|Zetterstéen|1987|p=785}}

[[File:Balami - Tarikhnama - Babak parleys with the Afshin Haydar, the Caliph al-Mu'tasim's general (cropped).jpg|thumb|right|upright=1.2|alt=Perso-Turkic miniature showing an armed horseman parlaying with a man within a castle, while several armed riders fight in the bottom|Babak parlays with al-Afshin, from [[Balami]]'s ''[[Tarikhnama|Tārīkhnāma]]'', 14th century]]
{{anchor|Babak}}The first major campaign of the new reign was directed against the [[Khurramites]] in [[Adharbayjan]] and [[Arran (Caucasus)|Arran]].{{sfn|Bosworth|1993|p=776}} The Khurramite revolt had been active since 816/7, aided by the inaccessible mountains of the province and the absence of large Arab Muslim population centres, except for a few cities in the lowlands. Al-Ma'mun had left the local Muslims largely to their own devices. A succession of military commanders attempted to subdue the rebellion on their own initiative, and thus gain control of the country's newly discovered mineral resources, only to be defeated by the Khurramites under the capable leadership of Babak.{{sfn|Kennedy|2004a|pp=164–165}} Immediately after his accession, al-Mu'tasim sent the Tahirid ''[[sahib al-shurta|ṣāḥib al-shurṭa]]'' of Baghdad and Samarra, Ishaq ibn Ibrahim ibn Mus'ab, to deal with an expansion of the Khurramite rebellion from [[Jibal]] into [[Hamadan]]. Ishaq swiftly achieved success, and by December 833 had suppressed the rebellion, forcing many Khurramites to seek refuge in the Byzantine Empire.{{sfn|Bosworth|1991|pp=2–3, 7}} In 835 al-Mu'tasim took action against Babak, assigning his trusted and capable lieutenant, al-Afshin, to command the campaign. After three years of cautious and methodical campaigning, al-Afshin was able to capture Babak at his capital of Budhdh on 26{{spaces}}August 837, extinguishing the rebellion. Babak was brought captive to Samarra, where, on{{spaces}}3 January 838, he was paraded before the people seated on an elephant, and then publicly executed.{{sfn|Mottahedeh|1975|p=75}}{{sfn|Bosworth|1991|pp=14–24, 36–93}}{{sfn|Kennedy|2001|pp=131–133}}

Shortly after, [[Mankjur al-Farghani|Minkajur al-Ushrusani]], whom al-Afshin had appointed as governor of Adharbayjan after the defeat of the Khurramites, rose in revolt, either because he had been involved in financial irregularities, or because he had been a co-conspirator of al-Afshin's. Bugha the Elder marched against him, forcing him to capitulate and receive a safe-passage to Samarra in 840.{{sfn|Gordon|2001|p=78}}{{sfn|Bosworth|1991|pp=175–178}}

{{anchor|Mazyar}}The second major domestic campaign of the reign began in 838, against Mazyar, the autonomous [[Qarinid]] ruler of Tabaristan.{{sfn|Kennedy|2004a|p=165}} Tabaristan had been subjected to Abbasid authority in 760, but Muslim presence was limited to the coastal lowlands of the [[Caspian Sea]] and their cities. The mountainous areas remained under native rulers—chief among whom were the [[Bavandids]] in the eastern and the Qarinids in the central and western mountain ranges—who retained their autonomy in exchange for paying a tribute to the Caliphate.{{sfn|Madelung|1975|pp=198–202}} With the support of al-Ma'mun, Mazyar had established himself as the ''de facto'' ruler of all Tabaristan, even capturing the Muslim city of [[Amol|Amul]] and imprisoning the local Abbasid governor. Al-Mu'tasim confirmed him in his post on his accession, but trouble soon began when Mazyar refused to accept his subordination to the Tahirid viceroy of the east, Abdallah ibn Tahir, instead insisting on paying the taxes of his region directly to al-Mu'tasim's agent.{{sfn|Kennedy|2004a|p=165}}{{sfn|Mottahedeh|1975|pp=75–76}}{{sfn|Madelung|1975|p=204}} According to al-Tabari, the Qarinid's intransigence had been secretly encouraged by al-Afshin, who hoped to discredit the Tahirids and assume their vast governorship in the east himself.{{sfn|Bosworth|1991|pp=137–138}}

Tension mounted as the Tahirids encouraged the local Muslims to resist Mazyar, forcing the latter to adopt an increasingly confrontational stance against the Muslim settlers and turn for support on the native Iranian, and mostly [[Zoroastrian]], peasantry, whom he encouraged to attack the Muslim landowners. Open conflict erupted in 838, when his troops seized the cities of Amul and [[Sari, Iran|Sari]], took the Muslim settlers prisoner, and executed many of them. In return, the Tahirids under [[al-Hasan ibn al-Husayn ibn Mus'ab]] and [[Muhammad ibn Ibrahim al-Mus'abi|Muhammad ibn Ibrahim ibn Mus'ab]] invaded Tabaristan. Mazyar was betrayed by his brother [[Quhyar]], who also revealed to the Tahirids the correspondence between Mazyar and al-Afshin. Quhyar then succeeded his brother as a Tahirid appointee, while Mazyar was taken captive to Samarra. Like Babak, he was paraded before the populace, and then flogged to death, on 6{{spaces}}September 840.{{sfn|Mottahedeh|1975|p=76}}{{sfn|Madelung|1975|p=205}}{{sfn|Bosworth|1991|pp=162–172, 179–180}} While the autonomy of the local dynasties was maintained in the aftermath of the revolt, the event marked the onset of the country's rapid Islamization, including among the native dynasties.{{sfn|Madelung|1975|pp=205–206}}

Near the end of al-Mu'tasim's life there were a series of uprisings in the Syrian provinces, including the revolt by Abu Harb, known as [[al-Mubarqa]] or "the Veiled One", which brought to the fore the lingering pro-[[Umayyad]] sentiment of several Syrian Arabs.{{sfn|Bosworth|1993|p=776}}{{sfn|Bosworth|1991|pp=194–196, 203–206}}

=== Confrontation with Byzantium ===
{{main|Sack of Amorium|Battle of Anzen}}
[[File:Byzantine-Arab wars, 837-838.svg|thumb|right|upright=1.2|alt=Geophysical map of Anatolia with the major cities and movements of the Byzantine and Arab armies marked|Map of the Byzantine and Abbasid campaigns in the years 837–838, showing [[Theophilos (emperor)|Theophilos]]'s raid into [[Upper Mesopotamia]] and al-Mu'tasim's retaliatory invasion of [[Asia Minor]], culminating in the conquest of [[Amorium]].]]
Taking advantage of the Abbasids' preoccupation with the suppression of the Khurramite rebellion, the Byzantine emperor Theophilos had launched attacks on the Muslim frontier zone in the early 830s, and scored several successes. His forces were bolstered by some 14,000 Khurramites who fled into the Empire, became baptized and enrolled in the Byzantine army under the command of their leader Nasr, better known by his Christian name [[Theophobos]].{{sfn|Treadgold|1988|pp=280–283}} In 837, Theophilos, urged by the increasingly hard-pressed Babak, launched a major campaign into the Muslim frontier lands. He led a large army, reportedly numbering over 70,000 men, in an almost unopposed invasion of the region around the upper [[Euphrates]]. The Byzantines took the towns of [[Zibatra]] (Sozopetra) and [[Arsamosata]], ravaged and plundered the countryside, extracted ransom from [[Malatya]] and other cities in exchange for not attacking them, and defeated several smaller Arab forces.{{sfn|Treadgold|1988|pp=286, 292–294}}{{sfn|Vasiliev|1935|pp=137–141}} As refugees began arriving at Samarra, the caliphal court was outraged by the brutality and brazenness of the raids; not only had the Byzantines acted in open collusion with the Khurramites, but during the sack of Zibatra all male prisoners were executed and the rest of the population sold into slavery, and some captive women were raped by Theophilos' Khurramites.{{sfn|Treadgold|1988|pp=293–295}}{{sfn|Vasiliev|1935|pp=141–143}}

The Caliph took personal charge of preparations for a retaliatory expedition, as the campaigns against Byzantium were customarily the only ones in which caliphs participated in person.{{sfn|Kennedy|2004a|p=164}} Al-Mu'tasim assembled a huge force—80,000 men with 30,000 servants and camp followers according to [[Michael the Syrian]], or even larger according to other writers—at [[Tarsus (city)|Tarsus]]. He declared his target to be [[Amorium]], the birthplace of the reigning Byzantine dynasty. The Caliph reportedly had the name painted on the shields and banners of his army. The campaign began in June, with a smaller force under al-Afshin attacking through the Pass of [[Hadath]] in the east, while the Caliph with the main army crossed the Cilician Gates from 19 to 21{{spaces}}June. Theophilos, who had been caught unaware by the two-pronged Abbasid attack, tried to confront al-Afshin's smaller force first, but suffered a major defeat at the [[Battle of Dazimon]] on 22{{spaces}}July, barely escaping with his life. Unable to offer any effective resistance to the Abbasid advance, the Emperor returned to Constantinople. A week later, al-Afshin and the main caliphal army joined forces before [[Ancyra]], which had been left defenceless and was plundered.{{sfn|Treadgold|1988|pp=297–302}}{{sfn|Vasiliev|1935|pp=144–160}}{{sfn|Bosworth|1991|pp=97–107}}

[[File:Byzantine emissaries to the Caliph.jpg|thumb|Byzantine envoys before al-Mu'tasim (seated, right), miniature from the ''[[Madrid Skylitzes]]'' (12th/13th century)]]
From Ancyra, the Abbasid army turned to Amorium, to which they laid siege on 1{{spaces}}August. Al-Afshin, Itakh, and Ashinas all took turns assaulting the city with their troops, but the siege was fiercely contested, even after the Abbasids, informed by a defector, effected a breach in a weak spot of the wall. After two weeks, taking advantage of a short truce for negotiations requested by one of the Byzantine commanders of the breach, the Abbasid army successfully stormed the city. It was thoroughly plundered and its walls razed, while the populace, numbering into the tens of thousands, was carried off to be sold into slavery.{{sfn|Treadgold|1988|pp=302–303}}{{sfn|Vasiliev|1935|pp=160–172}}{{sfn|Bosworth|1991|pp=107–117}} According to al-Tabari, al-Mu'tasim was now considering extending his campaign to attack Constantinople, when the conspiracy headed by his nephew, al-Abbas, was uncovered. Al-Mu'tasim was forced to cut short his campaign and return quickly to his realm, without bothering with Theophilos and his forces, stationed in nearby [[Dorylaion]]. Taking the direct route from Amorium to the Cilician Gates, both the Caliph's army and its prisoners suffered during the march through the arid countryside of central Anatolia. Some captives were so exhausted that they could not move and were executed, while others found in the turmoil the opportunity to escape. In retaliation, al-Mu'tasim, after separating the most prominent among them, executed the rest, some 6,000.{{sfn|Treadgold|1988|p=303}}{{sfn|Vasiliev|1935|pp=172–173}}{{sfn|Bosworth|1991|pp=118–119}}

[[File:Siege of Amorium.jpg|250px|thumb|Miniature depicting the [[sack of Amorium]] in 838]]
The sack of Amorium brought al-Mu'tasim much acclaim as a warrior-caliph and ''[[Ghazi (warrior)|ghāzī]]'' (warrior for the faith), and was celebrated by contemporaries, most notably in a famous ode by the court poet [[Abu Tammam]].{{sfn|Bosworth|1993|p=776}} The Abbasids did not follow up on their success. Warfare continued between the two empires with raids and counter-raids along the border, but after a few Byzantine successes a truce was agreed in 841. At the time of his death in 842, al-Mu'tasim was preparing yet another large-scale invasion, but the great fleet he had prepared to assault Constantinople was destroyed in a storm off [[Cape Chelidonia]] a few months later. Following al-Mu'tasim's death, warfare gradually died down, and the [[Battle of Mauropotamos]] in 844 was the last major Arab–Byzantine engagement for a decade.{{sfn|Vasiliev|1935|pp=175–176, 192–193, 198–204, 284}}