sentences:  Following the Battle of Avarayr in 451, Christian Armenians maintained their religion and Armenia gained autonomy.After the Sasanian period (428–636), Armenia emerged as Arminiya, an autonomous principality under the Umayyad Caliphate, reuniting Armenian lands previously taken by the Byzantine Empire as well.The principality was ruled by the Prince of Armenia, and recognised by the Caliph and the Byzantine Emperor.