<Li> Anarchy at Samarra <Ul> <Li> Fifth Fitna </Li> </Ul> </Li> <Ul> <Li> Fifth Fitna </Li> </Ul> <P> The Battle of the Zab (Arabic: معركة الزاب ‎) took place on the banks of the Great Zab river in what is now Iraq on January 25, 750 . It spelled the end of the Umayyad Caliphate and the rise of the Abbasids, a dynasty that would last (under various influences and with varying power) until the 13th century . </P> <P> In 747 a major rebellion broke out against the Umayyad Caliphate, which ruled most of the Middle East from 661 to 750 . The principal cause of the rebellion was the increasing gap between the outlying peoples of the Caliphate and the Damascus - based Umayyad government . The Umayyad - appointed governors of the Caliphate's various provinces were corrupt and interested only with personal gains . Additionally, the Umayyads claimed no direct descent from Muhammad, while the Abbasids did (they descended from Muhammad's uncle Abbas--a fact the latter used greatly during the revolution). </P>

The abbasid dynasty comes to power after the umayyad army is defeated at the battle of the zab