 Taking advantage of the Abbasids ' preoccupation with the suppression of the Khurramite rebellion , the Byzantine emperor Theophilos had launched a number of attacks on the Muslim frontier zone in the early 830s , and scored a few successes . His forces were also bolstered by some 14 @,@ 000 Khurramites who under their leader , Nasr , fled into the Empire , became baptized and enrolled into the Byzantine army under the command of Nasr , better known by his Christian name of Theophobos . In 837 , Theophilos , urged by the increasingly hard @-@ pressed Babak , launched a major campaign into the Muslim frontier lands , with an army reportedly numbering over 70 @,@ 000 men , whom he led in an almost unopposed invasion around the upper Euphrates . The Byzantines took the towns of Zibatra ( Sozopetra ) and Arsamosata , ravaged and plundered the countryside , extracted ransom from Malatya and other cities in exchange for not attacking them , and defeated a number of smaller Arab forces . As refugees began arriving at Samarra , the caliphal court was outraged by the brutality and brazenness of the raids : not only had the Byzantines acted in open collusion with the Khurramites , but during the sack of Zibatra all male prisoners were executed and the rest sold into slavery , and some captive women were raped by Theophilos ' Khurramites . 
