Yazid was known for his devilish character and brutish conduct. He was known as the most licentious of men. The people having known and understood the character of Yazid, formed a convenant by which Muawiyah could not appoint Yazid as his successor. There, however, existed an undertaking known to a few, whereby Muawiyah had pledged to appoint Imam Husain (A) as his successor. This undertaking was given by Muawiyah to Imam Hasan (A). Muawiyah violated this undertaking and nominated Yazid as his successor.
Yazid demanded allegiance from the Holy Imam Husain (A), who could have never agreed to it at any cost. The people, fearing death and destruction at the hands of the tyrant, had yielded to him out of fear. Imam Husain (A) said that come whatever may, he would never yield to the devil in place of God and undo what his grandfather, the Holy Prophet had established.
The refusal of the Holy Imam to pay allegiance to this fiend marked the start of the persecution of the Holy Imam. As a result, he had retired to Medina where he led a secluded life. Even here he was not allowed to live in peace, and was forced to seek refuge in Mecca where also he was badly harassed and Yezid plotted to murder him in the very precincts of the great sanctuary of Ka'aba.
In order to safeguard the great sanctuary, Imam Husain (A) decided to leave Mecca for Kufa just a day before the Hajj (pilgrimage). When asked the reason for the mysterious departure from Mecca, fore-going the pilgrimage which was to be held only the next day, Imam Husain (A) said that he would perform the year's pilgrimage at Kerbala, offering the sacrifice not of any animals, but of his kith and kin and some faithful friends.
When the Holy Imam with his encourage had reached Kerbala, he declared: “This is the land, the land of sufferings and tortures." He alighted from his horse, and ordered his followers to encamp there saying, "Here shall we and our children be martyred. This is the land about which my grandfather, the Holy Prophet had foretold, and his prophecy will certainly be fulfilled."
At dawn of l0th Muharram, the Imam glanced the army of Yazid and saw Ibn Sa'ad ordering his forces to march towards him. He gathered is followers and addressed them thus: "Allah has, this day, permitted us to be engaged in holy War, and He shall reward us for our Martyrdom. So prepare yourselves to fight against the enemies of Islam with patience and perseverance. O sons of the noble and self-respecting persons, be patient ! Death is nothing but a bridge which you must cross after facing trials and tribulations so as to reach the Heaven and its joys. Which of you do not like to go from this prison (world) to the lofty palaces (Paradise)?"
Having heard the Imam's address, all his companions were overwhelmed and cried out, "O our Master! We are all ready to defend you and your Ahlul-Bait, and to sacrifice our lives for the cause of Islam."
Imam Husain (A) sent out from his camp his followers one after another to fight and sacrifice their lives in the way of the Lord. Lastly, when all his men and children had laid down their lives, Imam Husain brought his six-month old baby son Ali Asghar, and holding him on his own hands, demanded some water for the baby, dying of thirst. The thirst of the baby was quenched by a deadly poisoned arrow from the brute forces, which pinned the baby's neck to the arm of the helpless father. At last when the six month old baby was also killed, Imam Husain (A) addressed God: "O Lord! your Husain has offered in your way whatever you had blessed him with. Bless your Husain, O Lord, with the acceptance of this sacrifice. Everything Husain could do till now was through your help and by your grace." Lastly Imam Husain (A) came into the field and was killed. The details of his merciless slaughter are heart-rending. The forces of Yezid, having killed Imam Husain (A), cut and severed his head from his body and raised it on a lance. The severed head of the Holy Imam began glorifying God from the point of the lance saying "Allaho Akbar." All glory be to God Who is the Greatest!