The Abbasid Dynasty, known to its supporters as the ‘blessed dynasty’, which imposed its authority on the Islamic empire in 132/750, claimed to inaugurate a new era of justice, piety and happiness. The dynasty ruled the Islamic Caliphate from 750 to 1258 AD, making it one of the longest and most influential Islamic dynasties. For most of its early history, it was the largest empire in the world, and this meant that it had contact with distant neighbors such as the Chinese and Indians in the East, and the Byzantines in the West, allowing it to adopt and synthesize ideas from these cultures.
The replacement of the Umayyads by the Abbasids in the leadership of the Islamic community was more than a mere change of dynasty. It was a revolution in the history of Islam, as important a turning point as the French and Russian Revolutions in the history of the west. The Umayyad administration (661-750) of the Islamic Empire created serious grievances among various political, religious, social and ethnic groups. Their monopoly of power denied other people important administrative positions and the accompanying privileges and benefits. The Umayyads favored Syrian Arabs over other Muslims and treated mawali, newly converted Muslims, as second class citizens. The most numerous group of mawali were the Persians, who lived side by side with Arabs in the east who were angry at the favor shown to Syrian Arabs. Together, they were ripe for rebellion. Other Muslims were angry with the Umayyads for turning the caliphate into a hereditary dynasty, for their over-dependence upon the bureaucracy of the preceding Byzantine Empire, for levying taxes forbidden by the Qur’an, and for their ethnocentric policies. Some believed that a single family should not hold power, while Shiites believed that true authority belonged to the family of the Prophet Muhammad through his son-in-law Ali, and the Umayyads were not part of Muhammad’s family.
The Umayyads were accused by several religious groups of having a weak commitment to Islam. It will be remember that the Abbasid originally came to power by utilizing the discontent of the different segments of the empire such as the shi’is, the kharijites, the religiously orthodox, the Persian and other malcontents. All these various groups who were angry with the Umayyads united under the Abbasids, who began a rebellion against the Umayyads in Persia. The Abbasids built a coalition of Persian mawali, Eastern Arabs, and Shiites. The Abbasids were able to gain Shiite support because they claimed descent from Muhammad through Muhammad’s uncle Abbas. Their descent from Muhammad was not through Ali, as Shiites would have preferred, but Shiites still considered the Abbasids better than the Umayyads. A Persian general, Abu Muslim, who supported Abbasid claims to power, led the Abbasid armies. His victories allowed the Abbasid leader Abul `Abbas al-Saffah to enter the Shiite-dominated city of Kufa in 748 and declare himself caliph. In 750, the army of Abu Muslim and al-Saffah faced the Umayyad Caliph Marwan II at the Battle of the Zab near the Tigris River. Marwan II was defeated, fled, and was killed. As-Saffah captured Damascus and slaughtered the remaining members of the Umayyad family (except for one, Abd al-Rahman, who escaped to Spain and continued the Umayyad Dynasty there). The Abbasids were the new rulers of the caliphate.
The 'Abbasid revolution marked the end of the Arab empire and beginning of an integrated Islamic society in which the underprivileged mawali- (non-Arab clients) played a crucial role in the evolution of a common culture based on Islam and the Arabic language. In 1902 Wellhausen wrote: "The 'Abbasids called their government the dawlah, i.e., the new era. The revolution affected at this time was indeed prodigious."
The Abbasids had led a revolution against the unpopular policies of the Umayyads, but those who expected major change were disappointed. Under the...