Battle of Karbalāʾ, (October 10, 680 [10th of Muharram, AH 61]), brief military engagement in which a small party led by al-Ḥusayn ibn ʿAlī, grandson of the Prophet Muhammad and son of ʿAlī, the fourth caliph, was defeated and massacred by an army sent by the Umayyad caliph Yazīd I. The battle helped secure the position of the Umayyad dynasty, but among Shīʿite Muslims (followers of al-Ḥusayn) the 10th of Muharram (or ʿĀshūrāʾ) became an annual holy day of public mourning.When Yazīd I succeeded his father, Muʿāwiyah I, to the caliphate in the spring of 680, the many partisans of Prophet Muhammad’s late cousin and son-in-law ImaʿAlī ibn Abī Ṭālib—who collectively felt that leadership of the Muslim community rightly belonged to the descendants of ʿAlī—rose in the city of Al-Kūfah, in what is now Iraq, and invited al-Ḥusayn to take refuge with them, promising to have him proclaimed caliph there. Meanwhile, Yazīd, having learned of the rebellious attitude of the Shīʿites in Al-Kūfah, sent ʿUbayd Allāh, governor of Al-Baṣrah, to restore order. The latter did so, summoning the chiefs of the tribes, making them responsible for the conduct of their people, and threatening reprisal. Al-Ḥusayn nevertheless set out from Mecca with all his family and retainers, expecting to be received with enthusiasm by the citizens of Al-Kūfah. However, on his arrival at Karbalāʾ, west of the Euphrates River, on October 10, he was confronted by a large army of perhaps 4,000 men sent by ʿUbayd Allāh and under the command of ʿUmar ibn Saʿd, son of the founder of Al-Kūfah. Al-Ḥusayn, whose retinue mustered only 72 fighting men, gave battle, vainly relying on the promised aid from Al-Kūfah, and fell with almost all his family and followers. The bodies of the dead, including that of al-Ḥusayn, were then mutilated, only adding to the consternation of later generations of Shīʿites.
Though it was a rash expedition, it did involve the grandson of the Prophet and thus many members of the Prophet’s family. Al-Ḥusayn’s devout partisans at Al-Kūfah, who by their overtures had been the principal cause of the disaster, regarded it as a tragedy, and the facts gradually acquired a romantic and spiritual colouring. ʿUmar, ʿUbayd Allāh, and even Yazīd came to be regarded by ʿAlī’s supporters as murderers, and their names have ever since been held accursed by Shīʿite Muslims. Shīʿites observe the 10th of Muharram as a day of public mourning; and, among Iranians especially, as well as in Karbalāʾ, passion plays (Arabic taʿziyyah) are enacted, representing the misfortunes of the family of ʿAlī. The tomb of the decapitated martyr al-Ḥusayn at Karbalāʾ is their most holy place.