square miles (13,400,000 km2), making it the largest empire the world had yet seen and the sixth largest ever to exist in history. Geographically, the empire was divided into several provinces, the borders of which changed numerous times during the Umayyad reign. Each province had a governor appointed by the caliph. However, for a variety of reasons, including that they were not elected by Shura and suggestions of impious behaviour, the Umayyad dynasty was not universally supported within the Muslim community. Some supported prominent early Muslims like Zubayr ibn al-Awwam; others felt that only members of Muhammad's clan, the Banu Hashim, or his own lineage, the descendants of Ali, should rule. There were numerous rebellions against the Umayyads, as well as splits within the Umayyad ranks (notably, the rivalry between Yaman and Qays). At the command of Yazid son of Muawiya, an army led by Umar ibn Saad, a commander by the name of Shimr Ibn Thil-Jawshan killed Ali's son Hussein and his family at the Battle of Karbala in 680, solidifying the Shia-Sunni split. Eventually, supporters of the Banu Hashim and the supporters of the lineage of Ali united to bring down the Umayyads in 750. However, the Shi‘at ‘Alī, "the Party of Ali", were again disappointed when the Abbasid dynasty took power, as the Abbasids were descended from Muhammad's uncle, ‘Abbas ibn ‘Abd al-Muttalib and not from Ali. Abbasid Caliphate (750–1517) Abbasid Caliphs at Baghdad In 750, the Umayyad dynasty was overthrown by another family of Meccan origin, the Abbasids. Their time represented a scientific, cultural and religious flowering. Islamic art and music also flourished significantly during their reign. Their major city and capital Baghdad began to flourish as a center of knowledge, culture and trade. This period of cultural fruition ended in 1258 with the sack of Baghdad by the Mongols under Hulagu Khan. The Abbasid Caliphate had however lost its effective power outside Iraq already by c. 920. By 945, the loss of power became official when the Buyids conquered Baghdad and all of Iraq. The empire fell apart and its parts were ruled for the next century by local dynasties. In the 9th century, the Abbasids created an army loyal only to their caliphate, composed predominantly of Turkic Cuman, Circassian and Georgian slave origin known as Mamluks. By 1250 the Mamluks came to power in Egypt. The Mamluk army, though often viewed negatively, both helped