By now Caliph Ali رضي الله عنه had lost control of the western provinces of Syria and Egypt and even of Iraq, which had been a strong base of support at the time of his election; he was in a precarious position. The Kharijites had deserted him and fought against him, accusing him of the grave sin of submitting his claim to the Caliphate to arbitration and thus degrading the supreme office of the Muslim world.

The rivalries of the Muslim leaders had become so abhorrent to these fanatics that they decided to rid Islam of Ali رضي الله عنه , Muawiya ibn Abi Sufyan رضي الله عنه and Amr ibn al-As رضي الله عنه by assassinating all three of them on the same day at public prayer. Their plot, however, did not work out as planned. Amrرضي الله عنه was unhurt in Fustat because he was, by chance, unwell on the day and his substitute was killed instead and Muawiya رضي الله عنه escaped with a slight injury in Damascus; but Ali رضي الله عنه was struck down by a fanatic Kharijite, Abdur Rahman ibn Muljamرضي الله عنه , on 20 January, at the door of the mosque in Kufa. Thus the fourth and last Orthodox or Rightly-guided' Caliph died from a mortal wound on his head at the age of just over sixty. He was interred at a spot six n-files west of Kufa, where afterwards the town of NAAFI was built. It later became one of the great centres of pilgrimage in Islam, especially for the Shi'ites.

After the death of Ali رضي الله عنه , his elder son from Fatima, Hasan رضي الله عنه ca.625 ca.669 was declared in Kufa to be the legitimate successor to the Caliphate. Muawiya, who had proclaimed himself Caliph the year before, successfully persuaded Hasan to abdicate in return for a substantial pension for himself and the family of Aliرضي الله عنه . Hasan رضي الله عنه , increasingly unwilling to plunge the Muslim community into yet another civil war, accepted the terms offered by Muawiya رضي الله عنه and abdicated (July) after a shadowy rule of six months.

He and his younger brother, Hussain رضي الله عنه then left Kufa for Madinah leaving the way open for Muawiyaرضي الله عنه to enter Kufa with no serious contender for the Caliphate to challenge him. He thus became the de facto ruler of the Islamic world. From then on, Hasan lived in retirement for eight years in Madinah where he died in 669 at the age of forty-five.