Mu'tasim, Al-

Succeeding his brother al-Ma'mun in 833, al-Mu'tasim was the first caliph to employ the Turkish mercenaries who later came to dominate the 'Abbasid dynasty. In 837 he crushed a revolt of Persian schismatics led by the rebel Babak, who was cooperating with the Greeks. After the Byzantine emperor Theophilus had laid waste the Muslim