After the third caliph Uthman's assassination by rebels in 656, the rebels and the townspeople of Medina declared Ali, a cousin and son-in-law of the Islamic prophet Muhammad, caliph. Some of Muhammad's companions including Talha ibn Ubayd Allah, Zubayr ibn al-Awam and Mu'awiya ibn Abi Sufyan (then governor of Syria), and Muhammad's widow A'isha, refused to recognize Ali. They called for revenge against Uthman's killers and the election of a new caliph through "shura" (consultation). These events precipitated the First Fitna (First Muslim Civil War). When Ali was assassinated by Abd-al-Rahman ibn Muljam, a Kharijite, in 661, his eldest son Hasan succeeded him but soon signed a peace treaty with Mu'awiya to avoid further bloodshed. In the treaty, Hasan was to hand over power to Mu'awiya on the condition that Mu'awiya be a just ruler and that he would not establish a dynasty. After the death of Hasan in 670, his younger brother Husayn became the head of the Banu Hashim clan to which the Islamic prophet Muhammad also belonged. Though his father's supporters in Kufa gave him their allegiance, he would abide to the peace treaty between Hasan and Mu'awiya as long as the latter was alive.