The Four Rightly Guided Caliphs
Abu Bakr al-Siddiq (11-13 AH / 632-634 CE): The Prophet’s closest companion and father-in-law. Held the community together after the Prophet’s death when several tribes apostatized (al-ridda) and refused to pay zakat. The Wars of Ridda successfully reintegrated Arabia. Began the compilation of the Quran in written form (the hafiz Zayd ibn Thabit led this effort, fearing loss of Quran with the deaths of memorizers at the Battle of Yamama).
‘Umar ibn al-Khattab (13-23 AH / 634-644 CE): The architect of Islamic empire. Under his leadership: Iraq was conquered from the Sassanid Empire; Egypt and Syria were conquered from the Byzantines; the Islamic calendar (hijri calendar) was formally established; the administrative structures of Islamic governance were created. Assassinated by a Persian slave.
‘Uthman ibn ‘Affan (23-35 AH / 644-656 CE): The standardization of the Quran into the Uthmani mushaf — a single authoritative text distributed to the major Islamic cities while dialectical variant copies were burned. This is the Quran Muslims recite today. His later years saw growing political opposition and rebellion. Assassinated by rebels.
Ali ibn Abi Talib (35-41 AH / 656-661 CE): The Prophet’s cousin and son-in-law. His caliphate was immediately contested — by A’isha’s faction (Battle of the Camel, 656 CE) and by Mu’awiya ibn Abi Sufyan of Syria (Battle of Siffin, 657 CE). The arbitration after Siffin led to the Kharijite rebellion and Ali’s assassination by a Kharijite.
The Ismaili Reading
The Ismaili tradition does not reject the historical achievements of the first caliphs, but holds that they occupied the zahir function of governance while the batin of prophetic succession — the Imamate — remained with Ali and his descendants. In this reading, Abu Bakr, ‘Umar, and ‘Uthman were legitimate political leaders of the Muslim community; Ali was both the legitimate political leader and the Imam with the Prophet’s batin knowledge.
See also: Ali Ibn Abi Talib, Prophet Muhammad, Sahaba, Seerah Final Years, Khilafa, Bohra History, Nass