Complex sentence: Effective control over entire Yemen was not achieved by the Umayyad Caliphate, imam Abdullah ibn Yahya Al-Kindi was elected in 745 AD to lead the Ibāḍī movement in Hadramout and Oman.
Split into simpler sentences: Effective control over entire Yemen was not achieved by the Umayyad Caliphate. Imam Abdullah ibn Yahya Al-Kindi was elected in 745 AD to lead the Ibāḍī movement in Hadramawt and Oman.