Complex sentence: Imam Husayn ibn Ali rejected the legitimacy of Yazid as Caliph, after which Yazid killed him, along with many of his family members and supporters in the Battle of Karbala on October 10,680.
Split into simpler sentences: Imam Husayn ibn Ali rejected the legitimacy of Yazid as Caliph. Hussain ibn Ali was martyred along with many of his family members and supporters in the Battle of Karbala on October 10,680.