According to one Islamic tradition, Muhammad's last words were: "Oh God, have pity on those who succeed me." His first four successors - two fathers-in-law and two sons-in-law - would have good reason to think those words prophetic.
Even as Muhammad lay dying in June 632 (his high fever and excruciating headaches indicate bacterial meningitis), the manoeuvring for the leadership of Islam had begun. Who would be the khalifa - or, in English, the caliph: the successor? It might have been simple enough if one of Muhammad's sons had survived, but all three had died in infancy. He was dying intestate - abtar, in the Arabic, meaning cut off, without male heirs - and without designating a successor, though everyone would claim that he had.
Sunnis - named for the sunna, the compiled reports of what Muhammad said and did - say he had indicated that his close companion and father-in-law Abu Bakr should take over. Shias say he appointed the philosopher-warrior Ali, his first cousin and son-in-law, and take their name from Shiat Ali, the followers of Ali.
And yet, in every statement and gesture cited, there was room for interpretation, an ambiguity that would lead to the first civil war in Islam, told in vivid detail by the classic 10th-century historian al-Tabari.
Even as Ali sat with Muhammad's body, the leadership nod went to Abu Bakr, whose daughter was Muhammad's most outspoken and unbiddable widow, Aisha. There had been bad blood between her and Ali ever since she had been suspected of adultery and Ali publicly advised Muhammad to divorce her. Even though she was vindicated, she never forgot; perhaps it was inevitable that she should eventually go into battle against Ali, the first and last time that a woman would lead Muslims to war.
No golden era
Abu Bakr died just two years after being appointed, the only one of the first four caliphs - known as al-rashidun, or the rightly guided ones - to die of natural causes. The others would be assassinated, two of them by fellow Muslims, a history far from the idealised Salafi idea of this as the golden era of the caliphate.
Once again, Ali was passed over. It was said that his nobility of spirit was exactly what worked against him - that he was too willing to forgo his claim to leadership and to live, as he put it, "with dust in my eyes and thorns in my mouth" in order to avoid the spectre of fitna, a word that literally means discord but would soon signify civil war. Yet each time Ali was passed over, the larger that spectre loomed.
The second caliph was another of Muhammad's fathers-in-law, the great military commander of Islam Umar. In a single decade, he won great victories over the Byzantine and Persian armies and led Islam into Egypt, Syria, Iraq and Persia, only to be assassinated by a Christian slave. With that, it seemed Ali's time at last had come, but it was a rival son-in-law who became the third caliph.
A scion of Mecca's ruling Umayyad clan, Uthman was known for his piety, but not for political skill. When officers of his own army, led by Ali's stepson, marched against him to protest the nepotism of his rule, he refused to talk with them. Exasperated, they besieged him in his palace and then stormed it, stabbing him 36 times and slicing off half the hand of his favourite wife, Naila, in the process.
The rebels acclaimed Ali as caliph, yet he rejected the title because he maintained that the caliphate had been corrupted; instead, he would be known as the Imam, with a definite capital "I", or the leader - the first of the Twelve Imams that the Shias consider to be the true successors of Muhammad. However, the murder of Uthman cast a shadow over the five years of Ali's rule.
Aisha stepped up to lead the cry of "revenge for Uthman" and mustered a 10,000-man army to confront Ali at Basra, in southern Iraq, at the Battle of the Camel in 656. The camel was hers, and by the end of the day, as she conceded defeat, Aisha's armoured howdah, or travelling seat, was reportedly so studded with arrows that it "bristled like a porcupine".
Ali ordered that she be accompanied back to Mecca, where she lived the rest of her life dictating her memoirs, becoming an important source of sunna reports on the Prophet's life and practice. Yet, for all Ali's magnanimity in victory, his rule was doomed. A far more powerful opponent than Aisha now confronted him. Muawiya, an Umayyad brother-in-law of Muhammad's and cousin of Uthman's, had been governor of Syria for 20 years, running it as his fiefdom. Now he set his eyes on controlling the whole empire.
Refusing to acknowledge Ali as the fourth caliph, he revived the call of revenge for Uthman; he also had both the third caliph's torn and bloody shirt and Naila's severed palm and fingers hung up on the main pulpit in Damascus in order to ginger up the troops.
Trial and tribulation
Muawiya is detested by the Shias, yet, were it not for him, the Muslim empire may never have survived. Unfettered by scruple or any claim to spiritual leadership, he made up for his unprepossessing appearance - protruding stomach, bulging eyes, feet swollen by gout - with a subtle political mind and the ruthlessness to exercise it, anticipating Machiavelli by nearly a millennium.
Unable to beat Ali in battle at Siffin, northern Syria, in 657, Muawiya instead manoeuvred his opponent into accepting arbitration. "After Siffin, I made war on Ali without armies and without exertion," he said with satisfaction. The outcome was fixed, and Ali stymied. Worse, a breakaway faction of Ali's followers turned on him, accusing him of betraying Islam by agreeing to human arbitration.
“Judgment belongs to God alone," they insisted, and early in 661 one of them assassinated the leader at his mosque in Kufa, today a suburb of the Iraqi city of Najaf.
That left Muawiya the uncontested caliph: not "righteous" but in firm control of a wealthy empire stretching from Libya in the west to the borders of India. Even then, time and prosperity might have healed the split if Muawiya had not succumbed to the dictator's weakness and become entranced by the idea of dynasty.
Muawiya died old, happy and newly pious, secure in the knowledge that his son Yazid would take over. But Yazid had none of his father's political skill, and relied instead on hardline repression. When Iraq rose up against him and called on Muhammad's grandson - Ali's son Hussein - to claim the caliphate, Yazid sent 4,000 troops to besiege Hussein and his band of 72 warriors on a stretch of stony desert not far from the Euphrates.
That barren stretch of land would become known as the city of Karbala, a name combining the Arabic words for trial and tribulation. The memory of the ensuing massacre, told and commemorated every year since 680 in the ten days of mourning known as Ashura, transformed Sunni history into Shia sacred history.
Where the historians stopped, the theologians took over - and with them the politicians, ready as always to manipulate piety for their own purposes.
Lesley Hazleton is the author of "After the Prophet: the Epic Story of the Shia-Sunni Split in Islam" (Doubleday, £16.64) and is now working on a biography of Muhammad. She blogs at: accidentaltheologist.com