The Imam was residing in Medina (Which now is called Mecca in Saudi Arabia), the Muslims in Iraq requested the Imams help in protecting them against the sinners that were slaughtering them. When He arrived, the sinners threatened to kill their wives and children if they followed the prophets will, which was for the people to follow Imam Ali. These threats had the intended affect on the people of Iraq, they all abandoned the Imam Hussein to fight the army alone which was sent by the sinners to slaughter the Imam. The sinners surrounded Imam Hussein, his family and the few followers he has, (which where 70 in number) in the city of Karbala. This situation continued for several days which meant that the Imam and his party were prevented from having access to water and food, even though the Fourat river was next to them. The Imam offered peace to the sinners, however, they responded on the 10th day by slaughtering the Imam, his family and all his followers. On this day all of His followers and all of the male members of his family which included a six month old baby boy were killed. All of the killings where accomplished in the most gruesome, inhuman and evil way possible. When all of His people were killed, the Imam was left alone to face an army of more than 70 000 solders of the sinners. The Imam was hit from every direction, He was bleeding from numerous wounds to his body. After the torturing of the Imam by the soldiers, they dismembered his head. His head was given to the sinners Prince as a gift.
Among the women in his party was his sister Zainab (peace be upon her) and her nephew whom was sick and not able to join the fight, and all the women where captured and imprisoned by the army. Zainab stood in front of the prince and gave a speech in front of the army and all the people. In Her speech She told the people about her brother the Imam and how they are the descendant of the prophet Mohammad, She also told them they are not sinners and are follows of Islam and not as they were informed by the prince and his people. After Zainabs speech, the people saw the truth which was that the Imam was a follower of Islam and a descendant of the prophet. When the prince saw that the people believed Zaiban and her nephew, he demanded that She stop.
All the soldiers that participated in killing the Imam died in painful and degrading manners over time. What this revolution achieved is that the blood was victorious on the sword.
Because the Imam sacrificed His blood (meaning life) we mourn his death each year.