The accession of al-Mutawakkil (r. 847–861) represented a significant break in the policies and personnel of the central government; not only did the new caliph bring an end to the mihnah and abandon Mu'tazilism, but he also set about removing the senior military and civil officials that had dominated the administrations of his two predecessors. As part of his campaign to weaken the old regime and strengthen his own hold on power, al-Mutawakkil relied on Ishaq to act against those officials who were too strong to be attacked in Samarra itself.[19]