On the tenth day of the month of Muharram in the year 680, the day called Ashura, Husayn and his companions, encamped at Karbala and cut off from the waters of the Euphrates, were surrounded and killed by the army of Yazid's governor. Husayn himself fell, and the men of his party with him; the women and children, including his surviving son Ali Zayn al-Abidin, were taken captive and brought to the caliph.
The bare fact of the killing is not in serious historical doubt; it is among the better-attested events of the early caliphate. What the tradition has made of it is a passion narrative of extraordinary power, the thirst of the besieged, the deaths of Husayn's companions and kin one by one, the killing of his infant son, and his own end, retold each year in minute and grieving detail.
For Shia Muslims Karbala is not merely a historical tragedy but the defining act of witness: the willing sacrifice of the Prophet's grandson against overwhelming and unjust power, a standing measure of the cost of refusing tyranny. Every day is Ashura, every land is Karbala expresses how the event is held as a perpetual present. The site of the battle, where Husayn is buried, is among the holiest places of Shia Islam and a destination of vast pilgrimage.