Background
Uthman ibn Affan became caliph in 644 following the assassination of his predecessor, Umar, having been elected by a consultative assembly (shura) of prominent companions of Muhammad. Uthman, a member of the Umayyad clan, began centralizing power through reliance on his Umayyad relatives, appointing kinsmen such as Marwan ibn al-Hakam and Sa'id ibn al-As to provincial governorships and granting them land and monetary favors, at the expense of other Quraysh and the Ansar who had previously held influence.
Opposition to Uthman's Policies
By around 650, general opinion had turned against Uthman. He faced accusations of nepotism and appointing unqualified young relatives to important posts. His declaration of Iraq's crown lands as state assets and demands that provincial surplus be forwarded to Medina fueled widespread opposition, especially in Iraq and Egypt. In Kufa, old settlers known as the qurra, led by Malik ibn al-Harith, expelled Uthman's governor Sa'id ibn al-As. In Egypt, Uthman's deposal of the popular Amr ibn al-As in favor of Abd Allah ibn Sa'd led to further unrest; by January 655, discontented Egyptians had ejected Ibn Sa'd and taken over the province's administration themselves. Senior companions, including Talha and Muhammad's widow A'isha, publicly criticized Uthman for nepotism and religious innovation.
Riot, Siege, and Assassination
Egyptian rebels who marched on Medina were initially persuaded to return home after mediation by Ali and Muhammad ibn Maslama, who guaranteed redress of grievances. However, the rebels intercepted a letter bearing Uthman's seal instructing the Egyptian governor to execute them upon return — a letter historians attribute to Marwan ibn al-Hakam rather than Uthman himself. The rebels returned to Medina and besieged Uthman's house. On Thursday, 16 June 656, a companion, Niyar ibn Iyad al-Aslami, was killed by a stone thrown by one of Marwan's servants while demanding Uthman's abdication, escalating tensions. The following day, Friday 17 June 656 (35 AH), rebels set fire to the doors of Uthman's house and forced their way in. Uthman had ordered his defenders to lay down arms to avoid bloodshed, though some, including Marwan and Sa'id ibn al-As, resisted and were wounded. Rebels climbed into the house from neighboring rooftops. According to the family tradition of Amr ibn Hazm, Muhammad ibn Abi Bakr struck the first blow, followed by further attacks from Kinana ibn Bishr al-Tujibi, Sudan ibn Humran, and Amr ibn al-Hamiq, killing Uthman. His body was buried at night in a Jewish cemetery, as rebels reportedly refused to allow burial in the Muslim cemetery.
Aftermath
Uthman's killing created an immediate succession crisis. Ali was elected caliph in Medina, but Mu'awiya (governor of Syria and Uthman's kinsman), along with Talha and al-Zubayr, demanded retribution before recognizing the new leadership, displaying Uthman's bloodied shirt and his wife Na'ila's severed fingers in Damascus. This dispute over justice for Uthman's death led directly to the First Fitna, including the Battle of the Camel and the Battle of Siffin.