The Umayyad Dynasty ruled the Islamic Caliphate from 660 to 750 CE, expanding the empire significantly. The Umayyad Caliphs conquered North Africa, Persia, Byzantine Empire, Spain, and Central Asia. They were successful military leaders and administrators who established an international postal system and standardized Arabic coinage and language. However, resentment grew due to their authoritarian rule as hereditary kings, favoring one tribe over others. This led to their eventual defeat and replacement by the Abbasid Dynasty in 750 CE.