6 – The Abbasid Revolt & fall of the Umayyad Caliphate (747-750)
While Marwan secured Iraq by suppressing the Kharijite rebellion, he had to quickly turn his attention to more unrest, this time in the east of the empire. Conflict arose against Nasr ibn Sayyar, the governor of Khurasan, and eventually, fighting broke out in the province as support for the Abbasids grew. One of the main players in the revolt was the Hashimiyya movement led by Abu Muslim.
Eventually, the Hashimiyya forces under the leadership of Qahtaba ibn Shabib al-Ta’i started to defeat the Umayyad in battle, and they won an important victory at Gurgan in 748 and captured the city of Rayy. Qahtaba had another crucial win at a battle near Isfahan the following year, and his son al-Hasan forced the city of Nihawand to surrender after a siege. Although the rebels suffered a blow when Qahtaba was killed in a surprise attack, his son led the army into Kufa.
Ibrahim the Imam probably began the Abbasid revolt but was captured and eventually executed by Marwan II. His brother, Abu al-Abbas as-Saffah, took over and was proclaimed caliph when al-Hasan captured Kufa. However, he still had to deal with Marwan and met his enemy at the Battle of Greater Zab in 750. As it transpired, it was one of the most important battles in history because it resulted in the establishment of an Abbasid dynasty that would last until the 13th century.
On paper at least, Marwan had a huge numerical advantage with an estimated force of at least 120,000 against the Abbasid army of approximately 35,000 which was led by Abdallah ibn Ali. However, Marwan’s army had no great love of their leader and morale was low after suffering several defeats earlier in the revolt. In contrast, the Abbasid army was united, and its morale had grown throughout the rebellion.
The Abbasids created a wall of spears, and their enemy made the astonishing mistake of charging right at them in the belief they could break the wall. In reality, the Umayyad charge was a catastrophe as a large percentage of the men involved were slaughtered. The rest of the army fell into disarray, and many of them drowned in the river. Marwan managed to escape to the small town of Abusir in the Egyptian Nile Delta. It was here that he met his death in a short battle and Abu al-Abbas became the new caliph.
The Abbasid Caliphate ruled until the Sack of Baghdad in 1258. Three years later, it moved to Cairo and continued to claim authority over religious matters until the Ottomans captured Egypt in 1517.