the succession arrangements he should have become caliph after the death of al-Muntasir. When he had signed away his rights to the caliphate in 862, he had been under duress to do so, with the Turks threatening to kill him if he refused, and therefore he considered the deed of abdication to be void. He also sought to convince the people that they could switch their allegiance to him without breaking the oath they had taken to serve al-Musta'in, and went through the effort to explain in detail how this could be done in a letter to Muhammad b. 'Abdallah. Al-Mu'tazz was initially accommodating toward those in Samarra who opposed his bid for the caliphate, and did not compel anyone to swear the oath to him if they refused to do so. He did, however, write to commanders stationed throughout the empire requesting their support, and soon reinforcements were arriving in Samarra. As the conflict progressed, he steadily gained followers as members of al-Musta'in's camp began to defect to him. He also made efforts to entice al-Musta'in's officers, writing offers to them and promising substantial rewards if they would switch their allegiance to him. Al-Mu'tazz's brother Abu Ahmad was put in charge of the Samarran forces at the beginning of the war. He was charged by the caliph with defeating al-Musta'in and Muhammad b. 'Abdallah, and was given the authority to command the army in any manner he pleased. Abu Ahmad's overall strategy was to keep Baghdad under constant attack from his troops, and to gain the surrender of the city by either assaulting it or starving its inhabitants until they lost the will to fight any longer. Toward this end, al-Mu'tazz sent armies to secure the neighboring towns that controlled access to Baghdad, and Abu Ahmad attempted to halt and seize any revenue shipments heading toward the city. The way in which Abu Ahmad ran the siege was not unquestionably accepted by al-Mu'tazz, who reportedly wrote him a letter in the middle of the war complaining of his lack of progress in forcing al-Musta'in's capitulation, but he remained in command of the main besieging force throughout the entire conflict. Abu Ahmad's army at the beginning of the siege numbered approximately 7,000 soldiers. Additional troops sent from Samarra a short time later increased its size to 11,000, though a large number of the reinforcements were killed soon after their arrival.