He supported his uncle Husayn ibn Ali in fighting off the Umayyad forces during the Battle of Karbala where he was killed[1][2] at the age of 13.
[3] Qasim was born the son of Hasan ibn Ali, the second Imam, and his wife Umm Farwa.
Hasan ibn Ali, Qasim's father died on the 28th Safar 50 AH (2 April 670 CE) by Mu'awiya I due to poisoning.
[8] Husayn and most of his family and companions, including Qasim ibn Hasan, were killed and then beheaded in the Battle of Karbala on 10 October 680 (10 Muharram 61 AH) by Yazid, and the women and children were taken as prisoners.
The letter stated: My son Qasim, a day will come when my brother Husayn will be facing an enemy army of tens of thousands.
[12] On 10 October 680 (Muharram 10, 61 AH), the day of Ashura, Qasim ibn Hasan was killed near the Euphrates, where Husayn and his followers were not allowed to get water.
Throughout history, many notable personalities, such as Nelson Mandela and Mahatma Gandhi,[14] have cited Husayn's stand against oppression as an example for their own fights against injustice.
The death of Husayn and his companions at Karbala is believed by both Shias and the Sunnis to be a sacrifice made to prevent the corruption of Islam by tyrannical rulers and to protect its ideology.