Abbasid (Civ3)/Civilopedia

The Arab descendants of Abbas, an uncle of the Prophet Muhammad, began a rebellion against the unpopular Umayyad Caliphate in 747 CE. Within a few years they had massacred most of the Umayyad dynasty and established the Abbasid Caliphate, which would last for the next five hundred years. At its greatest extent in the late 8th century, the Caliphate controlled Morocco on the Atlantic Ocean to central Asia as far as the borders of India. They also contributed much toward scientific progress at a time when European culture was stagnant and backwards.
One of the first things the Abbasids did was to move the administrative center away from Damascus to Mesopotamia. In 762 CE the second Abbasid caliph, al-Mansur, began the construction of a new capital city. The site he chose was on the banks of the Tigris at a small village called Baghdad. The new city was originally built with three concentric round walls. The caliphate palace and parks occupied the center and were surrounded by a ring of military barracks and offices, which in turn were surrounded by housing. Suburbs quickly appeared beyond the outer wall, and by 800 CE the city had half a million residents, and would continue to grow over the next several centuries. Because it was the principal trade center to the silks of China and the spices of India, Baghdad became the wealthiest city in the world at its height. It was filled with marble palaces of several stories, gardens, beautiful mosques, immense main avenues, and aqueducts.
Such wealth attracted invaders. By the early 10th century Buyid mercenaries from Iran gained temporal power, sacking parts of Baghdad in 945 CE, and subordinating the caliph to a puppet with spiritual authority at best. The Buyids in turn were pushed out by nomadic Seljuk Turks from Central Asia. The Muslim Seljuks also retained the caliph, respecting his symbolic role, but they were not averse to replacing him with another as desired.
After the Crusades eroded the Seljuk Empire in the 12th century, the Abbasid Caliphate regained secular power over southern Mesopotamia. However, within a hundred years, a new and merciless invader from the Asian steppes appeared. In 1258, the Mongols conquered Baghdad. They massacred hundreds of thousands of its citizens, razed the city, destroyed its irrigation system, and trampled Caliph al-Musta’sim to death with horses, thus bringing the Abbasid dynasty to a violent conclusion.