Islam under the Prophet Muhammad had been at war for the final dozen years of his life. That conflict devolved into an internal struggle over succession almost immediately after his death on June 8, 632. It was an enduring dispute that resulted in the division between Sunni Islam and Shia Islam that persists today.
The disagreement centered on a single question: should the Muslim community be led by a relative of the Prophet or by a trusted companion selected by those who had known him best? Who should succeed him as Islam’s patriarch and caliph?
Abu Bakr was followed by Umar, who expanded the Islamic state dramatically, conquering Egypt, Jerusalem, and Persia. His ten-year reign ended when a Persian captive assassinated him. On his deathbed, he assembled the six remaining members of Muhammad's original ten companions and instructed them to select his successor from among themselves. They chose Uthman ibn Affan as the third caliph, bypassing Ali once again.
During Uthman’s rule the empire continued expanding but also began to fracture under the weight of rapid growth and cultural diversity. Concerned that a number of variations of the Qur’an had emerged in Muslim-controlled lands and that they threatened religious unity, Uthman ordered the compilation of a single authoritative version of the Qur’an. While this decision standardized the text used today, it also sparked unrest that eventually culminated in rebellion and Uthman’s assassination.
After Uthman’s death, Ali accepted leadership of the caliphate. His supporters who believed him to be the rightful immediate heir to the Prophet Muhammad regard him not as the fourth caliph but as the first true leader of the Muslim community—the First Imam. They considered the other three to have been illegitimately selected in what amounted to a succession of coups by his three predecessors.
Ali immediately had to contend with a rebellion of his own. His chief rival was the Syrian governor Mu’awiyah I, cousin of the murdered Uthman and scribe to Muhammad. Mu’awiyah demanded justice for Uthman’s murder and withheld recognition of Ali’s authority because of it. Their rivalry led to the Battle of Siffin, a confrontation that ended inconclusively but hardened the emerging Sunni-Shiite divide.
In 661, Ali was praying during Ramadan when an assassin struck him with a poison-coated sword. He died two days later, leaving the caliphate to his son, Hasan ibn Ali. Hasan relinquished leadership over the caliphate to Mu’awiyah after his support eroded and negotiations ended the conflict. According to Shiite tradition, after Hasan’s abdication, he was poisoned by his wife, apparently on Mu’awiyah’s orders.
He was succeeded by his brother Husayn, the Third Imam. Husayn was killed and beheaded in 680 at the Battle of Karbala by forces loyal to Yazid I. Yazid was caliph in the Umayyad Caliphate.
So, Shiites regard Ali as the First Imam, Hasan as the Second, and Hasan’s brother Husayn as the Third. Shiite tradition holds that the Fourth, Fifth, Sixth, Seventh, Eighth, Ninth, Tenth, and Eleventh Imams—all direct descendants of Husayn—were systematically persecuted or killed by successive rulers of the Umayyad Caliphate and later the Abbasid Caliphate. Both caliphates are considered part of the Sunni political tradition.
Husayn’s death became the defining event in Shiite identity. It transformed the political dispute over succession into a sacred narrative of injustice, sacrifice, and ultimate redemption.
That redemption is to occur under the Twelfth Imam. Shiite tradition holds that the Twelfth Imam, Muhammad al-Mahdi, was a five-year-old leading the funeral prayer for his father in 874 when he disappeared. Believers claim that God concealed him and that he remains hidden in caves (or in a well, according to some) until it’s time for his return. When he reappears, he’s expected to establish justice and preside over a universal Islamic rule.
Both Sunnis and Shiites anticipate the coming of the Mahdi. The difference is that Shiites believe he is the hidden descendant of Ali, while Sunnis believe the Mahdi will arise from among the Muslim community.
That belief has never been merely theological. It has profound political implications too.
Shiite clerics who claim to have descended from the Prophet’s family
are known as Sayyids, a lineage traced through Muhammad’s daughter
Fatima and her husband Ali. Within Shiite society, that ancestry carries
enormous religious prestige and symbolic authority.
Former Iranian Supreme Leaders Ayatollah Ruhollah Khomeini and Ayatollah Ali Khamenei both claimed to be Sayyids and descent from Husayn through the line of Imams from Husayn.
When Khomeini led the Iranian Revolution in 1979, he didn't simply claim political authority; he invoked a lineage tied directly to the sacred history of the Imams. In doing that, he revived the narrative rooted in Husayn's martyrdom, the persecution and killing of successive Imams by worldly leaders, and the expectation of the return of the hidden Mahdi.
For many Shiite believers, the political struggles of the Iranian regime are not merely contemporary disputes but are part of a sacred history that began with the martyrdom of Husayn and continues until the return of the hidden Mahdi.
