Al-Musta'in

al-Musta'in bi-llah المستعين بالله
Caliph Commander of the Faithful
Gold dinar of al-Musta'in
12th Caliph of the Abbasid Caliphate
Reign	8 June 862 — 17 October 866
Predecessor	al-Muntasir
Successor	al-Mu'tazz
Born	c. 836 Samarra, Abbasid Caliphate
Died	17 October 866 (aged 29–30) Baghdad, Abbasid Caliphate
Issue	al-Abbas[1]
Names Abū al-ʿAbbās Aḥmad ibn Muḥammad ibn Muḥammad al-Mustaʿīn bi-ʾllāh
Dynasty	Abbasid
Father	Muhammad ibn al-Mu'tasim
Mother	Makhariq
Religion	Sunni Islam

Abū al-ʿAbbās Aḥmad ibn Muḥammad ibn Muḥammad al-Mustaʿīn bi-ʾllāh (Arabic: أبو العباس أحمد بن محمد بن محمد; 836 – 17 October 866), better known by his regnal title al-Mustaʿīn (836 – 17 October 866) was the Abbasid caliph from 862 to 866, during the "Anarchy at Samarra". After the death of previous Caliph, al-Muntasir (who had not appointed any successors), the Turkic military leaders held a council to select his successor. They were not willing to have al-Mu'tazz or his brothers; so they elected Ahmad ibn Muhammad (أحمد بن محمد), a nephew of al-Mutawakkil, who took the regnal name al-Mustaʿīn bi-ʾllāh (المستعين بالله "he who looks for help to God").

Arab and other troops based in Baghdad, displeased at the choice, attacked the assembly, broke open the prison, and plundered the armory. They were attacked by the Turkic and Berber soldiers, and after some fighting in which many died, succumbed.