his own caliphate. Madelung comments here that Mu'awiya later designated his son Yazid as his successor without any . As for whether and when Mu'awiya first aspired to the caliphate, it is the conclusion of Ayoub that he might have had two scenarios in mind: The first one was keeping the rule of Syria and annexing Egypt, as he indeed proposed to Ali's envoy, Jarir. Another clause of this same proposal was that Mu'awiya would not recognize the successor of Ali in case of his death, which suggests that Mu'awiya might have considered himself a candidate for the caliphate after Ali. The second scenario was that Mu'awiya would succeed in removing Ali from office. This is evident in some speeches and letters attributed to Mu'awiya before the Battle of Siffin, in which his case for the caliphate and seizing it by force is defended. Gaining political power by force soon became the common practice for Muslim rulers and was also legitimized by some (Sunni) jurists. Ali and retribution for Uthman Ali was openly critical of the conduct of Uthman, though he generally neither justified his violent death nor condemned his killers. While he did not condone the assassination, Ali probably held Uthman responsible through his injustice for the protests that led to his death, a view for which Poonawala cites Waq'at Siffin. From this same source, Ayoub cites the account of the negotiations before the Battle of Siffin, in which Ali is quoted as saying that Uthman was killed by those indignant about his transgressions. Even when pressed by Mu'awiya's envoys, the report adds that Ali refused to say that Uthman was killed wrongfully. Madelung sides with this judgment of Ali from a judicial point of view, saying that Uthman probably did not sanction the murder of Niyar ibn Iyad Aslami, which triggered the deadly raid on his residence, but he obstructed justice by preventing an investigation into the murder, fearing that his aide Marwan was behind it. Still, in his letters to Mu'awiya and elsewhere, Ali insisted that he would bring the murderers to justice in due course, probably after establishing his authority. Quoting al-Ya'qubi and al-Kufi, Ayoub suggests that a mob from various tribes murdered Uthman and that Ali could have not punished them without risking widespread tribal conflict, even if he could identify them. Here, the Islamicists Farhad Daftary and John Kelsay say that the actual murderers