Abbasids
The Abbasids were a dynasty of caliphs who ruled over the Islamic Empire from 750 to 1258 CE. They were descendants of Abbas, the uncle of the Prophet Muhammad. The Abbasid caliphate is considered one of the most influential and prosperous periods in Islamic history.

Conquest
The Abbasids came to power after overthrowing the Umayyad dynasty, which had ruled the Islamic Empire since 661 CE. The Abbasids' rise to power was marked by a period of revolutionary upheaval and discontent against the Umayyads. They capitalized on the support they received from various factions, including religious and ethnic groups such as the Shias, Persians, and non-Arab Muslims.

Key Points:
1. Revolt: The Abbasids started their campaign against the Umayyads in 747 CE, led by Abu Muslim, a general in their army. They gained significant support from various groups who were dissatisfied with Umayyad rule.
2. Battle of the Zab: The decisive battle between the Abbasid and Umayyad forces took place at the Zab River in 750 CE. The Abbasids emerged victorious, resulting in the downfall of the Umayyad dynasty.
3. Capital - Baghdad: After establishing their rule, the Abbasids chose Baghdad as their capital. This strategic location allowed them to govern the vast Islamic Empire effectively and maintain control over trade routes.
4. Golden Age: The Abbasid period is often referred to as the "Golden Age of Islam." During this time, there was a flourishing of arts, sciences, literature, and philosophy. Scholars from different cultures and religions contributed to the intellectual advancements of the empire.
5. Trade and Commerce: The Abbasids actively promoted trade and commerce, which led to economic prosperity. Baghdad became a major center of trade and attracted merchants from various parts of the world, including Europe, Africa, and Asia.
6. Decline: The Abbasid caliphate began to decline in the 9th century due to internal conflicts, regional revolts, and external invasions. The empire fragmented into smaller states called "emirates" and eventually collapsed with the Mongol conquest of Baghdad in 1258 CE.

The Abbasid dynasty played a significant role in shaping the Islamic Empire and its cultural and intellectual achievements. Their conquest over the Umayyads marked a turning point in Islamic history, leading to a new era of governance and cultural development.