Abū Isḥāq Muḥammad ibn Hārūn al-Rashīd (; October 796 – 5 January 842), better known by his regnal name al-Muʿtaṣim biʾllāh (, ), was the eighth Abbasid caliph, ruling from 833 until his death in 842. When al-Ma'mun died unexpectedly on campaign in August 833, al-Mu'tasim was thus well placed to succeed him, with the support of the powerful chief , Ahmad ibn Abi Duwad, he continued to implement the rationalist Islamic doctrine of Mu'tazilism and implementing policy.

A younger son of Caliph Harun al-Rashid (r. 786–809), he rose to prominence through his formation of a private army composed predominantly of Turkic slave-soldiers (, sing. ). This proved useful to his half-brother, Caliph al-Ma'mun, who employed al-Mu'tasim and his Turkish guard to counterbalance other powerful interest groups in the state, as well as employing them in campaigns against rebels and the Byzantine Empire.

Although not personally interested in literary pursuits, al-Mu'tasim also nurtured the scientific renaissance begun under al-Ma'mun. In other ways, his reign marks a departure and a watershed moment in Islamic history, with the creation of a new regime centred on the military, and particularly his Turkish guard. In 836, a new capital was established at Samarra to symbolize this new regime and remove it from the restive populace of Baghdad.

The power of the caliphal government was increased by centralizing measures that reduced the power of provincial governors in favour of a small group of senior civil and military officials in Samarra, and the fiscal apparatus of the state was more and more dedicated to the maintenance of the professional army, which was dominated by Turks. The Arab and Iranian elites that had played a major role in the early period of the Abbasid state were increasingly marginalized.

This strengthened the position of the Turks and their principal leaders, Ashinas, Wasif, Itakh, and Bugha. Another prominent member of al-Mu'tasim's inner circle, the prince of Ushrusana, al-Afshin, fell afoul of his enemies at court and was overthrown and killed in 840/1. The rise of the Turks would eventually result in the troubles of the 'Anarchy at Samarra' and led to the collapse of Abbasid power in the mid-10th century, but the -based system inaugurated by al-Mu'tasim would be widely adopted throughout the Muslim world.

Al-Mu'tasim's reign was marked by continuous warfare. The two major internal campaigns of the reign were against the long-running Khurramite uprising of Babak Khorramdin in Adharbayjan, which was suppressed by al-Afshin in 835–837, and against Mazyar, the autonomous ruler of Tabaristan, who had clashed with the Tahirid governor of Khorasan and risen up in revolt. While his generals led the fight against internal rebellions, al-Mu'tasim himself led the sole major external campaign of the period, in 838 against the Byzantine Empire. His armies defeated Emperor Theophilos and sacked the city of Amorium. The Amorium campaign was widely celebrated, and became a cornerstone of caliphal propaganda, cementing al-Mu'tasim's reputation as a warrior-caliph.

Early life

Muhammad, the future al-Mu'tasim, was born in the Khuld ("Eternity") Palace in Baghdad, but the exact date is unclear: according to the historian al-Tabari (839–923), his birth was placed by authorities either in Sha'ban AH 180 (October 796), or in AH 179 (Spring 796 or earlier). His parents were the fifth Abbasid caliph, Harun al-Rashid (), and Marida bint Shabib (), a slave concubine. Marida was born in Kufa, but her family hailed from Soghdia.

The young prince's early life coincided with what, in the judgment of posterity, was the golden age of the Abbasid Caliphate. The abrupt downfall of the powerful Barmakid family, which had dominated government during the previous decades, in 803 hinted at political instability at the highest levels of the court, while provincial rebellions that were suppressed with difficulty provided warning signals about the dynasty's hold over the empire. Nevertheless, compared to the strife and division that followed in the decades after Harun's death, the Abbasid empire was living through its halcyon days. Harun still ruled directly over the bulk of the Islamic world of his time, from Central Asia and Sind in the east to the Maghreb in the west. Lively trade networks linking Tang China and the Indian Ocean with Europe and Africa passed through the caliphate, with Baghdad at their nexus, bringing immense prosperity. The revenues of the provinces kept the treasury full, allowing Harun to launch huge expeditions against the Byzantine Empire and engage in vigorous diplomacy, his envoys arriving even at the distant court of Charlemagne. This wealth also allowed considerable patronage: charitable endowments to the Muslim holy cities of Mecca and Medina and the welcoming of religious scholars and ascetics at court secured the benevolence of the religious classes towards the dynasty, while the funds lavished on poets guaranteed its lasting fame; the splendour of the caliphal court provided the inspiration for some of the earliest stories of the One Thousand and One Nights.

Career under al-Ma'mun As an adult, Muhammad was commonly called by his kunya, Abu Ishaq. Al-Tabari describes the adult Abu Ishaq as "fair-complexioned, with a black beard the hair tips of which were red and the end of which was square and streaked with red, and with handsome eyes". Other authors stress his physical strength and his love for physical activity—an anecdote recalls how during the Amorium campaign he went ahead of the army riding on a mule and searched in person for a ford across a river—in stark contrast to his more sedentary predecessors and successors. Later authors write that he was almost illiterate, but as the historian Hugh Kennedy comments, this "would have been most improbable for an Abbasid prince", and most likely reflects his lack of interest in intellectual pursuits.

Activity during the civil war

As one of Harun's younger sons, Abu Ishaq was initially of little consequence, and did not figure in the line of succession. Soon after Harun died in 809, a vicious civil war broke out between his elder half-brothers al-Amin () and al-Ma'mun (). Al-Amin enjoyed the backing of the traditional Abbasid elites in Baghdad (the abnāʾ al-dawla), while al-Ma'mun was supported by other sections of the abnāʾ. Al-Ma'mun emerged victorious in 813 with the surrender of Baghdad after a long siege and the death of al-Amin. Choosing to remain in his stronghold in Khurasan, on the northeastern periphery of the Islamic world, al-Ma'mun allowed his main lieutenants to rule in his stead in Iraq. This resulted in a wave of antipathy towards al-Ma'mun and his "Persian" lieutenants, both among the Abbasid elites in Baghdad and generally in the western regions of the Caliphate, culminating in the nomination of Harun al-Rashid's younger brother Ibrahim as anti-caliph at Baghdad in 817. This event made al-Ma'mun realise his inability to rule from afar; bowing to popular reaction, he dismissed or executed his closest lieutenants, and returned in person to Baghdad in 819 to begin the difficult task of rebuilding the state.

Throughout the conflict and its aftermath, Abu Ishaq remained in Baghdad. Al-Tabari records that Abu Ishaq led the Hajj pilgrimage in 816, accompanied by many troops and officials, among whom was Hamdawayh ibn Ali ibn Isa ibn Mahan, who had just been appointed to the governorship of the Yemen and was on his way there. During his stay in Mecca, his troops defeated and captured a pro-Alid leader who had raided the pilgrim caravans. He also led the pilgrimage the following year, but no details are known. It appears that at least during this time, Abu Ishaq was loyal to al-Ma'mun and his viceroy in Iraq, al-Hasan ibn Sahl, but, like most members of the dynasty and the abnāʾ of Baghdad, he supported his half-uncle Ibrahim against al-Ma'mun in 817–819.

Formation of the Turkish guard From , Abu Ishaq began forming his corps of Turkish troops. The first members of the corps were domestic slaves he bought in Baghdad (the distinguished general Itakh was originally a cook) whom he trained in the art of war, but they were soon complemented by Turkish slaves sent directly from the fringes of the Muslim world in Central Asia, under an agreement with the local Samanid rulers. This private force was small—it probably numbered between three and four thousand at the time of his accession to the throne—but it was highly trained and disciplined, and made Abu Ishaq a man of power in his own right, as al-Ma'mun increasingly turned to him for assistance. For the first time, special military uniforms were introduced for this praetorian Turkic guard.

The long civil war shattered the social and political order of the early Abbasid state; the abnāʾ al-dawla, the main political and military pillar of the early Abbasid state, had been much reduced by the civil war. Along with the abnāʾ, the old Arab families settled in the provinces since the time of the Muslim conquests, and the members of the extended Abbasid dynasty formed the core of the traditional elites and largely supported al-Amin. During the remainder of al-Ma'mun's reign they lost their positions in the administrative and military machinery, and with them their influence and power. Furthermore, as the civil war raged in the eastern half of the caliphate and in Iraq, the western provinces slipped from Baghdad's control in a series of rebellions that saw local strongmen claiming various degrees of autonomy or even trying to secede from the caliphate altogether. Although he had overthrown the old elites, al-Ma'mun lacked a large and loyal power base and army, so he turned to "new men" who commanded their own military retinues. These included the Tahirids, led by Abdallah ibn Tahir, and his own brother Abu Ishaq. Abu Ishaq's Turkish corps was politically useful to al-Ma'mun, who tried to lessen his own dependence on the mostly eastern Iranian leaders, such as the Tahirids, who had supported him in the civil war, and who now occupied the senior positions in the new regime. In an effort to counterbalance their influence, al-Ma'mun granted formal recognition to his brother and his Turkish corps. For the same reason he placed the Arab tribal levies of the Mashriq (the region of the Levant and Iraq) in the hands of his son, al-Abbas.