Mutasem
Abu Ishaq 'Abbas al-Mu'tasem ibn Harun (794 – January 5, 842) was an Abbasid caliph (833 - 842). He succeeded his half-brother al-Ma'mun. He was hailed caliph on August 9, 833. One of the most difficult problems facing this Caliph, as faced his predecessor, was the uprising of Babak Khorramdin. Babak first rebelled in A.H. 201 (816-817) and overcame a number of caliphate forces sent against him. Finally, Mu'tasem provided clear instructions to his general Afshin Khaydhar ibn Kawus. Following these, Afshin patiently overcame the rebel, securing a ####significant victory of this reign. Babak was brought to Samarra in A.H. 223 (837-838). He entered the city spectacularly riding on a splendid elephant. He was executed by his own executioner and his head sent to Khurasan. His brother was executed in Baghdad. In that same year of Babak's death, the Byzantine emperor Theophilus launched an attack against a number of Abbasid fortresses. Mu'tasem launched a well planned response. Afshin met and defeated Theophilus on July 21, 838, known as Battle of Anzen. Ankyra fell to the Muslim army of 50,000 men and from there they advanced on the stronghold of Amorium. A captive escaped and informed the caliph that one section of Amorium's wall was only a frontal facade. By concentrating bombardment here, Mu'tasem captured the city. Mu’tasem also fought against Qarinids in Tabarestan and rebels in Damascus, in Palestine and in Jordan. Imam Javad “P.B.U.H” (The ninth Imam of Shias), was poisoned and martyred by Mu’tasem.
Sources :
Islamic encyclopedia
Wikipedia