 Al @-@ Mu 'tasim 's reliance on his ghilmān would increase in the aftermath of an abortive plot against him during the Amorium campaign in 838 . Headed by ' Ujayf ibn ' Anbasa , a long @-@ serving Khurasani who had served al @-@ Ma 'mun since the civil war against al @-@ Amin , the conspiracy rallied the traditional Abbasid elites , dissatisfied with al @-@ Mu 'tasim 's policies and especially his favouritism towards to the Turks . The plotters aimed to kill the Caliph and raise al @-@ Ma 'mun 's son al @-@ Abbas in his stead . According to al @-@ Tabari , al @-@ Abbas , although privy to these designs , rejected Ujayf 's urgent suggestions to kill al @-@ Mu 'tasim during the initial stages of the campaign , and the plot was soon uncovered . Al @-@ Abbas was imprisoned , and the Turkish leaders Ashinas , Itakh , and Bugha the Elder undertook to uncover and arrest the other conspirators . The affair was the signal for a large @-@ scale purge of the army of the remaining senior Iranian and abnāʾ officials and commanders — according to the Kitab al- ' Uyun , some seventy commanders were executed — while the influence of the Turkish leaders , who remained conspicuously loyal to al @-@ Mu 'tasim throughout the affair , correspondingly increased . The one exception to this purge of the Iranian element were the Tahirids , who remained in place as governors of their Khurasani super @-@ province , encompassing most of the eastern Caliphate . In addition , the Tahirids provided the governor of Baghdad , a focus of opposition to the Caliph under al @-@ Ma 'mun , which helped keep the city quiescent . The post was held throughout al @-@ Mu 'tasim 's reign by Ishaq ibn Ibrahim ibn Mus 'ab , who was " always one of al @-@ Mu 'tasim 's closest advisers and confidants " ( C. E. Bosworth ) . 
