The karbala war is a war that takes place in the same people, this war can be called the civil war in the second Islam which took place around the 10th of Muharram.
This war was caused by the struggle for the Caliphate carried out by the Umayyads who at that time declared themselves as the unilateral Khalifah of the Muslims.
Karbala is a war over the right of the Ahlul Bait (the family of the Messenger of Allah) that happened because it was a denial made by the Umayyad family by giving up the position of Caliph to his son, Yazid. The power of the Muawiyah Dynasty was planned since the reign of Umar and reached the peak in the reign of Hasan as, son of Ali ibn Abu Talib. At first Hasan did not want to pledge allegiance to Muawiyah, but for the sake of the salvation of the people and the widespread slander, Hasan was forced to pledge allegiance to Muawiyah.