Ali ibn Abi Talib was acclaimed in 656 CE as the fourth caliph after the death of the Islamic prophet Muhammad. Following the 656 assassination of the third caliph Uthman in Medina by provincial rebels who had grievances about injustice and corruption, the prophet's cousin and son-in-law was elected to the caliphate by the rebels, the Ansar (early Medinan Muslims), and the Muhajirun (early Meccan Muslims). While the election of Ali faced little opposition, his support was limited among the Quraysh, some of whom aspired to the caliphate. The Umayyads (Uthman's tribesmen) and some others thereby left Medina––some thus breaking their oaths of allegiance––and soon rebelled against Ali.
Background
Opposition to Uthman Ali frequently accused the third caliph Uthman of deviating from the Quran and the Sunna, and he was joined in this criticism by most of the senior companions. Uthman was also widely accused of nepotism, corruption, and injustice, and Ali is known to have protested his conduct, including his lavish gifts for his kinsmen. Ali also protected outspoken companions, such as Abu Dharr and Ammar, against the wrath of the caliph. Ali appears in early sources as a restraining influence on Uthman without directly opposing him. Some supporters of Ali were part of the opposition to Uthman, joined in their efforts by Talha and Zubayr, who were both companions of Muhammad, and by his widow Aisha. Among the supporters of Ali were Malik al-Ashtar () and other religiously-learned (). These wanted to see Ali as the next caliph, though there is no evidence that he communicated or coordinated with them. Ali is also said to have rejected the requests to lead the rebels, although he might have sympathized with their grievances, and was thus considered a natural focus for the opposition, at least morally. It is also likely that some companions supported the protests with the hope of either deposing Uthman, or changing his policies, thus underestimating the severity of the opposition to Uthman.
Assassination of Uthman
As their grievances mounted, discontented groups from provinces began arriving in Medina in 35/656. On their first attempt, the Egyptian opposition sought the advice of Ali, who urged them to send a delegation to negotiate with Uthman, unlike Talha and Ammar, who might have encouraged the Egyptians to advance on the town. Ali similarly asked the Iraqi opposition to avoid violence, which was heeded. He also acted as a mediator between Uthman and the provincial dissidents more than once to address their economical and political grievances. In particular, he negotiated and guaranteed on behalf of Uthman the promises that persuaded the rebels to return home and ended the first siege. Ali then urged Uthman to publicly repent, which he did. The caliph soon retracted his statement, however, possibly because his secretary Marwan convinced him that repentance would only embolden the opposition. On their way back home, some Egyptian rebels intercepted an official letter ordering their punishment. They now returned to Medina and laid siege to Uthman's residence for a second time, demanding that he abdicates. The caliph refused and claimed he was unaware of the letter, for which Marwan is often blamed in the early sources. Ali and another companion sided with Uthman about the letter, and suspected Marwan, while a report by the Sunni al-Baladhuri () suggests that the caliph accused Ali of forging the letter. This is likely when Ali refused to further intercede for Uthman. That Ali was behind the letter is also the opinion of Leone Caetani (). Giorgio Levi della Vida () is unsure, while Wilferd Madelung strongly rejects the accusation, saying that it "stretches the imagination" in the absence of any evidence. In turn, he accuses Marwan, the bellicose secretary of Uthman, while Hugh N. Kennedy holds Uthman responsible for the letter. The caliph was assassinated soon afterward in the final days of 35 AH (June 656) by the Egyptian rebels during a raid on his residence in Medina.
Role of Ali in the assassination Ali played no role in the deadly attack, and his son Hasan was injured while guarding Uthman's besieged residence at the request of Ali. He also convinced the rebels not to prevent the delivery of water to Uthman's house during the siege. Beyond this, historians disagree about his measures to protect the third caliph. Ali is represented by al-Tabari () as an honest negotiator genuinely concerned for Uthman. Husain M. Jafri () and Madelung highlight multiple attempts by Ali for reconciliation, and Martin Hinds () believes that Ali could not have done anything more for Uthman. Reza Shah-Kazemi points to Ali's "constructive criticism" of Uthman and his opposition to violence, while Moojan Momen writes that Ali mediated between Uthman and the rebels, urging the former to alter his policies and refusing the requests from the latter to lead them. This is similar to the view of John McHugo, who adds that Ali withdrew in frustration when his peace efforts where thwarted by Marwan. Fred Donner and Robert Gleave suggest that Ali was the immediate beneficiary of Uthman's death. This is challenged by Madelung, who argues that Aisha would have not actively opposed Uthman if Ali had been the prime mover of the rebellion and its future beneficiary. He and others observe the hostility of Aisha toward Ali, which resurfaced immediately after his accession in the Battle of the Camel (656). Laura Veccia Vaglieri () notes that Ali refused to lead the rebellion but sympathized with them and possibly agreed with their calls for abdication. Hossein Nasr and Asma Afsaruddin, Levi della Vida, and Julius Wellhausen () believe that Ali remained neutral, while Caetani labels Ali as the chief culprit in the murder of Uthman, even though the evidence suggests otherwise. Mahmoud M. Ayoub () notes the often pro-Umayyad stance of the Western classical orientalists, with the exception of Madelung.
Ali and retribution for Uthman Ali was openly critical of the conduct of Uthman, though he generally neither justified his violent death nor condemned the killers. While he did not condone the assassination, Ali probably held Uthman responsible through his injustice for the protests which led to his death, a view for which Ismail Poonawala cites Waq'at Siffin. Madelung sides with this judgement 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 the Shia al-Ya'qubi () and Ibn A'tham 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, Farhad Daftary says that the actual murderers soon fled Medina after the assassination, a view for which Jafri cites al-Tabari. Closely associated with Ali was Malik al-Ashtar, a leader of the , who had led the Kufan delegation against Uthman, even though they heeded Ali's call for nonviolence, and did not participate in the siege of Uthman's residence. A leading Egyptian rebel with links to Ali was his stepson, Muhammad ibn Abi Bakr, who was allegedly among those who killed Uthman. Some authors have rejected this accusation, though most seem to agree that Muhammad visited Uthman shortly before his death and rebuked him for his conduct. These two men and some other supporters of Ali were implicated by Mu'awiya in the assassination of Uthman. As such, some authors suggest that Ali was unwilling or unable to punish these individuals. The revenge for Uthman soon became the pretext for two revolts against Ali.
Support In the aftermath of the assassination, the potential candidates for the caliphate were Ali and Talha, though some suggest that Talha lacked any popular support, and that Ali was thus the obvious choice. After the assassination of Uthman, his tribesmen (the Umayyads) fled Medina, and the rebels and Medinans thus controlled the city. While Talha may have enjoyed some support among the Egyptian rebels, Ali was preferred by most of the Ansar (early Medinan Muslims) and the Iraqi rebels, who had earlier heeded Ali's call against violence. Alternatively, a report by al-Tabari suggests that the Basran and Kufan opposition supported Talha and Zubayr, respectively. After the assassination, the report continues, both groups supported Ali. Poonawala, Moojan Momen, Jafri, Donner, and Sean Anthony add the majority of the Muhajirun (early Meccan Muslims) to the above list of Ali's supporters. The key tribal chiefs also favored Ali at the time, writes Ira M. Lapidus.
Reluctance of Ali The caliphate was offered by these groups to Ali, who was initially reluctant to accept it, saying that he preferred to be a minister (). Reza Aslan attributes this reluctance to the polarizing impact of the assassination on the community, while Will Durant () writes, "[Ali] shrank from drama in which religion had been displaced by politics, and devotion by intrigue." For Jafri, Ali must have been wary of implicating himself in Uthman's regicide by becoming the next caliph. For Veccia Vaglieri, however, that Ali allowed himself to be nominated by the rebels was an error, because it left him exposed to accusations of complicity in the assassination. Alternatively, M.A. Shaban and Anthony believe that Ali stepped in to prevent chaos and fill the power vacuum created by the regicide. The opinion of Ayoub is close. Soon after, possibly when it became clear that he enjoyed popular support, Ali accepted the caliphate, demanding a public pledge at the mosque, according to al-Tabari and al-Baladhuri. Shah-Kazemi and Jafri maintain that Ali was compelled by popular pressure to accede, with the latter author presenting as evidence an address in Nahj al-balagha, attributed to Ali at the Battle of the Camel.
Pledges
Ali received the public pledge of allegiance in the Prophet's Mosque in Medina, possibly the day after Uthman's murder, though Poonawala and a report by al-Tabari place the ceremony several days later. It appears that Ali personally did not force anyone for pledge. Among others, Sa'ad ibn Abi Waqqas, Abd-Allah ibn Umar, and Usama ibn Zayd refused to give their oaths, though the case of Usama is challenged by Madelung who concludes that he pledged allegiance to Ali but did not fight in his battles. To this list Ayoub adds Sa'id ibn al-As, al-Walid ibn Uqba, and Marwan, suggesting that these three withheld their pledge because of their personal grudges against Ali. The Shia scholar Muhammad H. Tabatabai () further adds Amr ibn al-As, Busr ibn Abi Artat, Samura ibn Jundab, and al-Mughira, claiming that those opposed to Ali are often guilty in the historical sources of religious transgressions. On the whole, Madelung suggests that there is less evidence for any violence here than in the case of the first caliph Abu Bakr (), even though many broke with Ali later, claiming that they had pledged under duress. At the same time, that the majority favored Ali in Medina might have created an intimidating atmosphere for those opposed to him. McHugo suggests that Malik al-Ashtar and some others may have contributed to this atmosphere, probably without the approval of Ali.
Talha and Zubayr