Al-Husain (AS), the second child of Ali and Fatimah, was born in the year 4 AH, and after the martyrdom of his elder brother, al-Hasan, became his successor. Husain was Imam for 10 years which was mostly during the reign of Muawiyah, except the last 6 month which coincided with the reign of Yazid. Imam Husain lived under the most difficult conditions of suppression and persecution.
This was due to the fact that, first of all, religious laws and regulations had lost much of their weight and credit, and the edicts of the Umayyah government had gained complete authority and power. Secondly, Muawiyah and his fans made use of every possible means to put aside the Household of prophet and to move them out of the way. Above all, Muawiyah wanted to strengthen the basis of future kingdom of his son, Yazid, who because of his lack of principles and scruples was opposed with a large group of Muslims. Therefore, in order to quell all opposition, Muawiyah had undertaken more severe means until he died in 60 AH and his son Yazid took his place.

Giving the oath of allegiance, was an old Arab practice which was carried out in important matters like governorship. Well-known people would give the oath of allegiance as a sign of agreement and obedience to their king and showing their support for his future actions. Braking the agreement after the oath of allegiance, was considered as a definite crime.

Muawiyah during his life time, had asked well-known people to give the oath of allegiance to Yazid, but did not impose this request upon Imam Husain. He particularly told Yazid in his last will that if Imam Husain refused to give the oath of allegiance, he should take it easy because Muawiyah knew the bad consequences of such enforcement. However because of his egoism and recklessness, Yazid neglected his father's advice, and immediately after taking over the power, ordered the governor of Medina to either take the pledge of allegiance from Imam Husain, or send his head to Damascus.
After the governor of Medina informed this demand to him, Imam Husain asked for a delay to think about the matter, and moved with his family toward Mecca overnight. He sought refuge in the sanctuary of God in Mecca which is official place of refuge in Islam. This happened at the beginning of Shaban 60 AH. Imam Husain stayed in Mecca for nearly four month.

This news spread throughout the Islamic world, and many people who were tired of inequalities during Muawiyah reign and were even more disturbed when Yazid took over, corresponded with Imam Husain and expressed their sympathy for him. On the other hand, a flood of letters began to flow, specially from Iraq and particularly from the city of Kufah, inviting the Imam to go there and to build up a government. Naturally such situation was dangerous for Yazid.

The stay of Imam Husain in Mecca continued until the season of pilgrimage when Muslims from all over the Islamic world came to Mecca to perform Hajj.The Imam realized that some of the followers of Yazid had entered Mecca as pilgrims with the mission of killing Imam during the ceremonies of Hajj with the arms they carried under the special pilgrimage dress.

In order to safeguard the great sanctuary of Mecca, Imam Husain decided to leave for Iraq before completing the ceremony of Hajj. When he was asked the reason for the mysterious departure, Imam Husain said that he would perform this year's pilgrimage in the desert of Karbala, offering the sacrifice of not any animals, but himself and his family and friends. Giving a short speech in the vast crowd of people, he announced that he was setting for Iraq, and said he would be martyred. He asked people to join him in attaining the goal of offering their lives in the path of God.

Imam Husain was determined not to give his allegiance to Yazid and fully knew that he would be killed. But it was not the time to save the life. That moment was the right time to water the faded lawn of Islam by his blood. Some of outstanding people of Mecca stood in the way of Imam Husain and warned him the danger of the move he was making. But he answered that he refused to pay allegiance and to give his approval to a government of injustice and tyranny. He added that wherever he would go, he would be killed, so he would leave Mecca in order to preserve the respect for the House of God, and not to allow this respect be destroyed by letting his blood spilled there.

While on the way of Kufah, he received the striking news that under the pressure of Yazid's agents, people of Kufa did not support his representatives and turned back, and some of them joined the Yazid's army to kill Imam's representatives in Kufah. The feet of those martyrs were tied and they were dragged through the streets of Kufah. The city and its surroundings were under very strict marshal law by countless soldiers of enemy who where waiting to face Imam. There was no way for Imam to turn into unless to march ahead and face the death.

Approximately 44 miles from Kufah, in a desert called Karbala, Imam and his followers were surrounded by the army of Yazid. They cut off the water supply of the Household of Prophet and their companions and their families among them were many women and children. For eight days they stayed in that place under the heat of the sun, and the circle among them narrowed and the number of enemy's army increased by a number of 30,000 fully equipped soldiers of Yazid.

In the following night, Imam gathered his companions and gave the a short speech saying that there was nothing ahead but martyrdom. He added that since the enemy was concerned only with his person, he would free them from all obligations so that any one who wished could escape in the darkness of the night and save his life. Then he ordered the lights to be turned off, and most of his companions who had joint him for their own advantages, dispersed. Only those whose hearts were tested by Allah remained who were about 40 companions and some from Bani Hashim (his relatives).
Once again, Imam gathered those who remained to put them on the test. He addressed his companions and Hashimite relatives, repeating that enemy was only concerned with him and they could escape the danger in the darkness of night. But this time the faithful companions answered each in own way that they would not deviate from the right path and would never leave him alone. They said that they would defend the Household of Prophet to the last drop of their blood as long as they could carry a sword.

The enemy intended to start the war in the eve of the ninth day of the month, but Imam asked for a delay till next morning to worship all over the night for the last time. During the night, some 30 soldiers of enemy joint Imam, among them was Hurr who was one of the Generals of the army of enemy. They finally chose their way to be with Imam, and Imam accepted their repentance. In this way the number of his followers became close to 90 people consisting of 72 companions and 18 male members of his family and relatives, while enemy was more than 45,000 by then.

On the tenth of Muharram of the year 61 (680) That inequitable war began. That day, they fought from morning till their final breath, and all the companions and the relatives were martyred. Among those who were killed were two children of Imam Hasan, only thirteen and eleven years old, and a five years old child of Imam Husain.

When Imam himself was ready to fight, he saw his six-month-old baby is dying from thirst. Imam brought his infant near to enemy demanded some water for baby, saying: You want me but not this baby so take him and give him some water. The words of Imam has not been finished that the thirst of the baby was quenched by a deadly poisoned arrow from enemy which pinned the baby's neck to the arm of his father. Imam threw some of his blood toward sky saing: "O' Lord! Your Husain has offered whatever You have given him. Bless me by acceptance of this sacrifice." Finally Imam came to the field and fought for a long time and was finally martyred. The army of Yazid having killed Imam Husain, cut his head and raised it on a lance.

The army of enemy, after ending the war, burned the tents of women and children accompanying Imam and his companions, and plundered those helpless women. They decapitated the bodies of the martyrs, denuded them and threw them to the ground without burial. Then they moved women and children along with the heads of the martyrs to Kufah. The bodies of the martyrs were under the sunshine for three days till a tribe passing that place found them and performed the burial.

The event of Karbala, the capture of women and children of the Household of Prophet, their being taken as prisoners from town to town, and the speeches made by Zaynab, the daughter of Ali, who was one of the prisons, became a scandal for Umayyah Kingdom. Such abuse of the Household of Prophet nullified the propaganda which Muawiyah had built up for years. The scandal reached to the extent that Yazid denounced the action of his agents in public. That was what excactly Imam Husain wanted to do, otherwise he would not bring women and children with him and sacrifice some, and let the rest to become captives. That was the only way to make a wave in order to awaken the Muslim nation.

The event of Karbala was a major factor in the overthrow of Umayyah kingdom though its effect was delayed. Among its immediate results were the revolts and rebellions combined with bloody wars which continued for twelve years. During those riots non of the important elements in Karbala could escape revenge and punishment, including Yazid.
Muhammad Iqbal (from Lahore, Pakistan) said:

"Imam Husain uprooted despotism forever till the day of Judgment. He watered the dry garden of freedom with surging wave of his blood, and indeed he awakened the sleeping Muslim nation. If Imam Husain had aimed at acquiring a worldly empire, he would not have traveled he did. Husain weltered in blood and dust for the sake of truth. Verily he, therefore, became bed-rock (foundation) of the Muslim creed; There is no God but Allah."

Charles Dickens had said the following about Imam Husain (AS):

"If Husain fought to quench his worldly desires, then I do not understand why his sisters, wives and children accompanied him. It stands to reason therefore that he sacrificed purely for Islam."

Thomas Carlyle has relayed this about the Tragedy of Karbala:

"The best lesson which we get from the tragedy of Karbala is that Husain and his companions were the rigid believers of God. They illustrated that numerical superiority does not count when it comes to truth and falsehood. The victory of Husain despite his minority marvels me!"

The famous, Dr. K. Sheldrake on Imam Husain (AS) said this:

"Husain marched with his little company not to glory, not to power or wealth, but to a supreme sacrifice and every member of that gallant band, male and female, knew that the foes were implacable, were not only ready to fight but to kill. Denied even water for the children, they remained parched under a burning sun, amid scorching sands yet no one faltered for a moment and bravely faced the greatest odds without flinching."

World famous Arab historian al-Fakhri has said this about Imam Husain's sacrifice:

"This is a catastrophe whereof I care not to speak at length, deeming it alike too grievous and too horrible. For verily, it was a catastrophe than that which naught more shameful has happened in Islam...There happened therein such a foul slaughter as to cause man's flesh to creep with horror. And again I have dispersed with my long description because of it's notoriety, for it is the most lamented of catastrophes."