Today in Middle Eastern history: the Battle of the Zab (750)

If you’re interested in history and foreign affairs, Foreign Exchanges is the newsletter for you! Sign up for free today for regular updates on international news and US foreign policy, delivered straight to your email inbox, or subscribe and unlock the full FX experience:


Today is the anniversary of the Battle of the Zab, which took place in 750 and was the climactic battle in the Abbasid Revolution that ousted the Umayyad dynasty from the caliphate. Obviously it would be difficult to describe the battle without going over the causes of the revolution, but equally obviously we could be here for many thousands of words discussing an event as large in scale and impact as the Abbasid Revolution. So I’ll try to stick to some basic bullet points. The extremely short explanation is this: a whole bunch of people in the caliphate had become very, very fed up with living under Umayyad rule.

Traditionally historians identify three categories of fed up folks in this period: the early Shiʿa, non-Arab Sunnis, and non-Muslims. But there’s an additional factor involved which has to do with the third caliphal civil war, or fitna, which began in 744 and, depending on how you look at it, either ended sometime in the late 740s or lingered until 750, when it stopped being an Umayyad civil war and became the Abbasid revolution. The war had its roots, as did a lot of self-destructive imperial behavior under the Umayyads, in the tribal rivalry between the Qays and Yaman factions, something we've talked about in more detail elsewhere.

When the caliph al-Walid II took the throne in 743, he was known for many things. Some of these were good, like his purported kindness to the disadvantaged. Some seem nice but may not have been well regarded in a ruler, like his fondness for writing poetry. And some were viewed quite negatively, like his fondness for getting drunk. None of these traits suggested that Walid would be a particularly strong or capable ruler, and indeed there were people who took advantage of the caliph’s lack of attention to the details of running his dominion. One of these was a man named Yusuf ibn Umar al-Thaqafi, the governor of Iraq. Yusuf was an arch-Qaysi who hated the Yamani faction and, through a combination of influence peddling and bribery, was able to convince the caliph to elevate the Qays at the expense of the Yamanis. Naturally this caused some resentment, and the Yamanis, along with some other factions who felt they’d been wronged by the caliph and/or were just displeased with his erratic/immoral behavior, ousted and executed Walid in 744. They replaced him with his cousin, Yazid III, though the coup leader and real power in the caliphate was Sulayman b. Hisham, the son of Walid's predecessor, Hisham b. Abd al-Malik.

It was at this point that another Umayyad cousin, the future Marwan II, seems to have started thinking about making a move for the throne. His window to the top job was then thrown wide open when Yazid died unexpectedly only six months into his reign, possibly of brain cancer. Qaysi tribes, eager for revenge on their Yamani rivals, flocked to Marwan, and the sheer size of his army seems to have been enough to put the Umayyad leaders in Damascus into a panic. Sulayman, along with the new caliph—Yazid’s brother Ibrahim—fled the capital without a fight, and Marwan entered and was crowned caliph in December 744. Revolts broke out everywhere—among the Yamani tribes in the Levant, among the early Shiʿa in Iraq, and in Egypt, whose governor seems to have just been tired of taking orders from Syrians. Marwan put these revolts down but the unity of the caliphate was shattered.

As for those discontented groups I mentioned above, the grievances were all longstanding. The Shiʿa, supporters of the former caliph Ali and his family, had been upset since Ali’s assassination in 661, or at least since his son Husayn’s martyrdom at the Battle of Karbala in 680. Non-Arab Muslims faced heavy discrimination under the Umayyads, even though from a religious perspective they were considered equal to Arab Muslims in every way. They were generally forced to subordinate themselves to an Arab tribe in which they could never become full members, and many even still had to pay the poll tax that only non-Muslims were supposed to pay. These conditions naturally created resentment, especially in Iran where there was a pretty concerted effort on the part of early governors to suppress the Persian language and any traces of Persian culture. If non-Arab Muslims were upset over being treated like non-Muslims, then you can imagine how non-Muslims felt. Those extra taxes hurt no matter who you were. Any restrictions non-Arabs faced in terms of social advancement were even more heavily felt by non-Muslims. And where non-Arab Muslims were merely regarded as second-class humans, non-Muslims could be subject to heavy persecution, even when they belonged to communities (Christians and Jews, for example) that weren’t supposed to be persecuted.

Even among Arab Muslims, I should note, there was a fair amount of resentment at the favoritism the Umayyads showed toward their Syrian base. That resentment was tied up to some extent in the Qays/Yaman rivalry, but it’s not exactly the same thing. It revealed itself in some of those rebellions that cropped up after Marwan II consolidated his power in around 747 or so. That revolt in Egypt I mentioned above was a prime example. And there were other revolts in far-off corners of the caliphate. One in particular, in Khurasan (eastern Iran/western Afghanistan today), caught fire and grew into the revolution that is our topic today.

Finally, the Umayyads also lost the support of a considerable portion of the religious scholarly community. Some of this was due to a late-Umayyad oppression of the Qadariyah theological school, which taught that humans have free will and are not bound by predestination. The broader issue was that many scholars chafed at the idea of the Umayyad caliphs asserting their prerogatives over religious matters when for most of them (like the oft drunken Walid) their only apparent qualification to serve as caliph was inheritance. There was a feeling that the leader of the Islamic community ought to have something more recommending him than his parentage.

This feeling was most prevalent among the Shiʿa, interestingly enough, since even though they argued that the imam/caliph should be a descendant of Muhammad (or at least Ali), they based that argument on the belief that the family of the Prophet possessed special intrinsic knowledge of the faith, a spark of enlightenment, and not simply on bloodlines. But there were non-Shiʿa scholars who also came to view the Umayyads collectively as morally unfit to hold high office. The Umayyads didn’t help themselves here when they changed the title of their office from the modest khalifat rasul Allah (“successor of the Messenger of God”), used by the early caliphs, to khalifat Allah (“vicegerent of God”), a much loftier standard and one to which most Umayyad caliphs failed to live up.

Despite all this opposition, the overthrow of the Umayyads was no mere formality. Marwan’s military prowess was very real and makes the Abbasid victory at the Zab something of a surprise. His army was primarily made up of his own veterans, who had amply demonstrated their toughness and military capability by this point in campaigns against the Byzantines and in putting down all those other rebellions. They were under the direct command of Marwan himself, and although he may not personally have been all sunshine and rainbows, the future caliph had impressive credentials as a military leader. He’d been governor of the northernmost provinces of the empire, which meant direct responsibility for conducting raids against neighboring Christian kingdoms like the Byzantines and Georgia. That meant he knew how to handle an army on campaign and in the field, which by this point was more than most Umayyad princes could say.

The Abbasids, however, were no slouches either. Their troops mostly came from communities in Khurasan (an area that stretches from eastern Iran into Afghanistan in modern terms) that were true frontier areas. When they weren't campaigning against their Central Asian neighbors to expand their territory, they were defending what they’d won against those same Central Asian neighbors trying to win it back. They were seasoned fighters. They'd been built into an army by a man named Abu Muslim, who had recruited them under his banner on behalf of...somebody. The thing is, he didn’t reveal exactly who was behind the movement (Abu al-Abbas, aka the future Caliph al-Saffah) until 749, well after the rebellion was underway and after his fighters were already committed to the war.

The first Abbasid caliph, al-Saffah, receives oaths of loyalty in Kufa, from a manuscript of Abu Ali Muhammad Balʿami's 10th century chronicle (Wikimedia Commons)

In not immediately declaring what his rebellion was about or for whom it had been raised, Abu Muslim cleverly offered up his movement as a cypher for anyone who had grievances with the Umayyad dynasty. Whether you were angry at their perceived impiety, were fed up with their perceived corruption, or were a disaffected Yamani/Shiʿa/non-Arab Muslim/non-Muslim/something else, Abu Muslim’s agenda-free revolution probably seemed like it had been launched just for you. Of course it wasn’t, but by the time people learned that the ball was already rolling too fast to do anything about it. This characteristic of the revolution wound up even working against Abu Muslim himself. He was executed by Caliph al-Mansur in 755, after finally realizing (to his disgruntlement) that he’d mostly just traded one ruling dynasty for another—and also because al-Mansur rightly perceived a disgruntled Abu Muslim to be a potential threat. In death, Abu Muslim became a symbol for several uprisings by Shiʿa and by non-Muslims, groups that had been unhappy under the Umayyads and found that life under the Abbasids wasn’t all that different.

But we’re getting way ahead of ourselves. Abu Muslim was still very much alive and gruntled at this point. His army had already been successful against several smaller Umayyad forces on the way from Khurasan to Iraq, so they were energized and confident in their chances. At Zab they were under the overall command of al-Saffah’s uncle, Abdullah b. Ali, though Abu Muslim led them in the field.

As you might expect from a battle fought in 750, at a time when historical record-keeping was haphazard and Umayyad record-keeping virtually non-existent, we don’t know a whole lot about the specifics of this engagement. What we “know” we know from later, Abbasid-friendly accounts whose reliability is questionable both because of chronology and the biases of the authors. But since they're the best we can do as far as accounts, let’s assume that at least the broad strokes are mostly accurate.

The two armies met at the Great Zab River, which starts in what is today southeastern Turkey and merges into the Tigris River south of Mosul. Marwan’s army is said to have been three or even four times the size of the Abbasid force, and while I suspect some of that can be chalked up to later creative license I think it’s reasonable to assume that the Umayyads outnumbered their enemies. The rebels apparently adopted a favorite tactic of the Umayyads, the spear wall, and let the Umayyad cavalry charge right into it and get slaughtered. If you need a mental picture, you can probably use the “Battle of Stirling” from the film Braveheart, though you should probably bear in mind that the actual Battle of Stirling Bridge wasn’t anything like the way it’s portrayed in that movie. But I digress. With its cavalry wiped out, the rest of the Umayyad army ran, many of its soldiers drowning in the river in their flight. Marwan himself managed to get all the way to Abusir, not far from modern Cairo, before the Abbasids caught up to him and killed him, bringing his dynasty to its end. To be completely fair, a few Umayyad survivors did eventually make their way west, where they eventually founded a new caliphate. But that caliphate was pretty removed from the old one.