Politically, the Umayyads focused on border expansion and a clear dilineation between Muslims and non-Muslims. The Umayyad's first problem was dealing with the line of succession after Muhammad's death. This created social unrest in the Umayyad caliphate. As well as differences between the Sunnis and Shi'a, non-Muslims could not hold office, further increasing social unrest. As the Umayyad's expanded across North Africa, into Spain, and as far as Southeast Asia, new tax systems further separated Muslims from non-Muslims. Dhimmis, or non-Muslims living in the caliphate, were taxed at a higher rate, which served as an early backbone to the Umayyads. However, many Buddhists and Hindus in South and Southeast Asia converted to Islam due to its egalitarian nature- it did not matter what social class to which you belonged because all were equal in Allah's eyes. As more people converted to Islam, tax revenues decreased, and this rapidly brought the Umayyad dynasty to a close.
The Abbasids conquered the Umayyads in 750 and set up the capital in Baghdad. While the Umayyads adopted many ruling techniques from the Byzantines, the Abbasids took their cues from the ancient Persians. Thus, the Abbasids were more inclusive than their predecessors. All non-Arab Muslims were given full citizenship in the caliphate, and different territories had governers that would report back to the main bureaucratic hub in Baghdad (this relates back to Persia's satrap system). Ultimately, the governors gained power for themselves and stopped paying tribute to Baghdad, which ripped apart Abbasid economy. An invasion by the Seljuk Turks finished the Abbasid caliphate in the mid 13th century.