What is "al-mu'tasim"

Abū Isḥāq Muḥammad ibn Hārūn al-Rashīd (; October 796 – 5 January 842), better known by his regnal name al-Muʿtaṣim bi’llāh (, "he who seeks refuge in God"), was the eighth Abbasid caliph, ruling from 833 to his death in 842. A son of Harun al-Rashid, he succeeded his half-brother al-Ma'mun, under whom he had served as a military commander and governor. His reign was marked by the introduction of the Turkish slave-soldiers ( ghilmān or mamālīk) and the establishment for them of a new capital at Samarra. This was a watershed in the Caliphate's history, as the Turks would soon come to dominate the Abbasid government, eclipsing the Arab and Iranian elites that had played a major role in the early period of the Abbasid state. Domestically, al-Mu'tasim continued al-Ma'mun's support of Mu'tazilism and its inquisition ( miḥna), and centralised administration, reducing the power of provincial governors in favour of a small group of senior civil and military officials in Samarra. Al-Mu'tasim's reign was also marked by continuous warfare, both against internal rebellions like the Khurramite revolt of Babak Khorramdin or the uprising of Mazyar of Tabaristan, but also against the Byzantine Empire, where the Caliph personally led the celebrated Sack of Amorium, which secured his reputation as a warrior-caliph.