The Abbasid Caliphate ruled the Islamic world from 750 to 1258 AD. It was one of the largest empires in the world during its early history and it was also one of the “longest and most influential Islamic dynasties”. Its decline happened slowly beginning with Caliph al-Ma’mun’s (813–833) reign.
Over time, as different Caliph’s came to power, their influence over the people and the region rose and fell due to many different factors. Eventually, they were primarily just figure heads. The last Caliph, al-Mu`tasim (r. 1242–1258), turned to the Mongols for help against his chief rival and ruler of Persia, the Sultanate of Khwarazm. However, the Mongols turned against al- Mu`tasim, surrounded Baghdad, killed the caliph, and completely destroyed the city.