Abbasid revolution

The Abbasid revolution (Arabic: اَلثَّوْرَة اَلْعَبَّاسِيَّةِ‎, romanized: aṯ-Ṯawra al-ʿAbbāsiyyah), was the overthrow of the Umayyad Caliphate (661–750), the second of the four major caliphates in Islamic history, by the third, the Abbasid Caliphate (750–1517).

The Abbasid revolt originated in the eastern province of Khorasan in the mid-8th century, fueled by widespread discontent with Umayyad rule. The Abbasids, claiming descent from Muhammad's uncle Abbas, capitalized on various grievances, including discrimination against non-Arab Muslims (mawali), heavy taxation, and perceived impiety of Umayyad rulers. Led by Abu Muslim Khorasani, Abu Muslim's army composed largely of Arab settlers disillusioned with Umayyad rule, marched under black banners, forming a powerful force that swept westward in open revolt, defeating Umayyad forces. The decisive Battle of the Zab in 750 saw the Abbasid army triumph over the last Umayyad caliph, Marwan II. This victory led to the fall of the Umayyad dynasty and the establishment of Abbasid rule, marking a significant shift in the caliphate's power base from Syria to Iraq and ushering in a new era of Islamic governance.

By the 740s, the Umayyad Empire found itself in critical condition. A succession crisis in 744 led to the Third Fitna, which raged across the Middle East for three years. The very next year, al-Dahhak ibn Qays al-Shaybani initiated a Kharijite rebellion that would continue until 746. Concurrent with this, a rebellion broke out in reaction to Marwan II's decision to move the capital from Damascus to Harran, resulting in the destruction of Homs – also in 746. It was not until 747 that Marwan II was able to pacify the provinces; the Abbasid revolution began within months.

Nasr ibn Sayyar was appointed governor of Khorasan by Hisham ibn Abd al-Malik in 738. He held on to his post throughout the war of succession, being confirmed as governor by Marwan II in the aftermath.

Khorasan's expansive size and low population density meant that the Arab denizens – both military and civilian – lived largely outside of the garrisons built during the spread of Islam into Persia. This was in contrast to the rest of the Umayyad provinces, where Arabs tended to seclude themselves in fortresses to avoid interacting with the locals. Arab settlers in Khorasan left their traditional lifestyle and settled among the native Iranian peoples. While intermarriage with non-Arabs elsewhere in the Empire was discouraged or even banned, it slowly became a habit within eastern Khorasan; and the Arabs began adopting Persian dress and as the two languages influenced one another, the ethnic barriers gradually eroded.

Support for the Abbasid revolution came from people of diverse backgrounds, with almost all levels of society supporting armed opposition to Umayyad rule. This was especially pronounced among Muslims of non-Arab descent, though even Arab Muslims resented Umayyad rule and centralized authority over their nomadic lifestyles. Both Sunnis and Shias supported efforts to overthrow the Umayyads, as did non-Muslim subjects of the empire who resented religious discrimination.

Following the Battle of Karbala, which led to the massacre of Husayn ibn Ali, the grandson of the prophet Muhammad, alongside his kin and companions by the Umayyad army in 680 CE, the event became a rallying cry of opposition against the Umayyads. The Abbasids also used the memory of Karbala extensively to gain popular support against the Umayyads, which further rallied Shi'ite support. In the decades preceding the Abbasid revolution, several Shi'ite and Alid uprisings had taken place against the Umayyads. To an extent, rebellion against the Umayyads bore an early association with Shi'ite ideas. This included the Tawwabin uprising led by Sulayman ibn Surad in 684–685 and Mukhtar al-Thaqafi's uprising in 685–687, following the murder of Husayn ibn Ali in 680. Later on, the Revolts of Zayd ibn Ali in 740 and the uprising of Abd Allah ibn Mu'awiya in 747–748, who even established temporary rule over Iran, paved way for the Abbasid revolution.

The Hashimiyya movement (a sub-sect of the Shi'ite Kaysanites) was largely responsible for starting the final efforts against the Umayyad dynasty, initially with the goal of replacing the Umayyads with an Alid ruling family. Initially, the Abbasid family kept quiet about their identity, simply stating that they wanted a ruler from the descendant of Muhammad upon whose choice as caliph the Muslim community would agree to. Many Shi'ites naturally assumed that this meant an Alid ruler, a belief which the Abbasids tacitly encouraged to gain Shi'ite support. The Abbasids claimed that Abu Hashim, the grandson of Ali through his son Muhammad ibn al-Hanafiyyah, had formally transferred the Imamate to Muhammad ibn Ali ibn Abdallah in 717, and thus Imamah was transferred to the house of al-Abbas.