The Battle of Karbala occurred because al-Ḥusayn ibn ʿAlī, grandson of Prophet Muhammad, refused to recognize the legitimacy of Umayyad caliph Yazīd I. Invited by the people of Kūfah, Ḥusayn planned to lead a revolt against the Umayyads.
Yazīd learned about the rebellious attitude of the Shiʿah in Kūfah and sent 4,000 men to confront Ḥusayn. On Muharram 10, 61 ah (October 10, 680 ce), Ḥusayn and his small band of followers were killed by the Umayyad forces at Karbala. The battle helped solidify the Umayyad dynasty’s position, but it also deepened the divide between Sunni and Shiʿi Muslims.