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 Umayyads from the caliphate. You can find out more about the revolution elsewhere on this blog, but the battle itself deserves a little mention.
The Umayyad army was primarily made up of Syrian Arabs, who had amply demonstrated their toughness and military capability by this point in campaigns against the Byzantines and in putting down several previous rebellions. They were under the direct command of Caliph Marwan II himself, and Marwan, although he may not personally have been all sunshine and rainbows, 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. He’d also taken the caliphate by force–not inheritance–in 744, and had held it through substantial turmoil.
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 hardened, crack fighters. They’d been built into an army by Abu Muslim, who had recruited them under his banner on behalf of…somebody–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 soldiers were already committed to the war.
This, by the way, was a pretty clever way to make the Abbasid Revolution into a cypher for anyone who had issues with the Umayyad dynasty. Whether you were angry at their perceived impiety, fed up with their perceived corruption, mad about their perceived preference for Syrian Arabs over everybody else, a disaffected early Shiʿa, or something else, Abu Muslim’s largely agenda-free revolution must have seemed like it had been launched just for you. Of course it wasn’t, but by the time people learned that it was too late to do anything about it. This characteristic of the revolution wound up even working against Abu Muslim himself–he was executed by the Caliph al-Mansur in 755, after finally realizing (to his disgruntlement) that he’d mostly just traded one dynasty for another–and because al-Mansur rightly perceived him to be a threat.
Abu Muslim’s 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 formal command of al-Saffah’s uncle, Abdullah b. Ali.
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 the battle. 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 Greater Zab River in northern Iraq. 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, even though the actual Battle of Stirling Bridge wasn’t anything like the way it’s portrayed in the movie. 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 final end. Well, not exactly final, but you get the idea.