The event marks the anniversary of the Battle of Karbala when Imam Husayn ibn Ali, a grandson of Muhammad the founder of Islam, and a Shia Imam, was killed by the forces of the second Ummayad caliph Yazid I. The event is marked by arranging 'majalis' (gatherings) to review Islamic teachings and to commemorate Husayn's sacrifice. The mourning reaches its climax on the tenth day, known as Ashura, on which the forces of Yazid killed the 72 individuals who fought, including Husayn and his family and supporters. The women and children left living were enslaved and transported to Yazid's court in Damascus.
Zainab and Zain-ul-Abideen informed the people that Yazid had martyred Imam Husayn and seventy-two of his companions including his six month old son Ali Asghar, and that their women and children were taken as prisoners to Syria.
When word of the mourning reached Yazid he decided to release the captive women and children from the prison in Damascus, out of fear of public revolt against his rule. He sent for Imam Zain-ul-Abideen, informed him of the impending release and asked if he wished for anything further. Zain-ul-Abideen said he would consult with Bibi Zainab. She asked Yazid to provide a place where the people could mourn for Imam Husayn and others of Muhammad's household. A house was provided, and here Zaynab binte Ali held the first Majlis-e-Aza of Imam Husayn and started the Mourning of Muharram.
Commemoration of the tragedy at Karbala reached its apogee in the mid-nineteenth century. By then it had spread across a vast area, extending from the Middle East and the Caucasus eastwards to India, Indonesia, and Thailand, and it had even been established in Trinidad by Indian Muslim migrants. In Iran, the memory of Karbala came to permeate social and cultural life, with mourning assemblies and dramatic performances (not all shias agree with the re-enacting of the tragedy of Karbala however) being organized throughout the year, not only in Muharram. The occasion might be furnished by the death of a revered person or the need to fulfill a vow. Gatherings known as sofra (lit. tablecloth), in which the preparation and serving of food played a focal role, were exclusively feminine: the preachers as well as the mourners were all women, and the lives and tribulations of women such as Fatimah and Zaynab were the principal topic of commemoration. Gatherings of this type appear to have originated in the late nineteenth century.
In the Twelver Usooli and Akhbari branches, mourners, both male and female, congregate together (in separate sections) for sorrowful, poetic recitations performed in memory of the death of Husayn, lamenting and grieving to the tune of beating drums and chants of "Ya Husayn." Passion plays are also performed, reenacting the Battle of Karbala and the suffering and death of Husayn at the hands of Yazid. They offer condolences to Imam-e-Zamana also known as Imam al-Mahdi whom they believe will avenge the blood of Husayn and bring justice to the world.
Twelver Alevis do not mourn at all, but instead fast during the event and use it as an opportunity for self-reflection. The only Ismaili group which mourns are the Mustaali, who mourn similarly to Usooli.
For the duration of the remembrance, it is customary for mosques to provide free meals (nazar) on certain nights of the month to all people. These meals are viewed as being special and holy, as they have been consecrated in the name of Imam Husayn, and thus partaking of them is considered an act of communion with Allah, Imam Husayn, and humanity.
In South Asia, a number of literary and musical genres, produced by both Shias and Sunnis, that have been inspired by the Battle of Karbala are performed during the month, such as marsiya, noha and soaz. This is meant to increase the peoples understanding of how the enemies fought The Battle of Karbala against Husayn and his followers. In Trinidad and Tobago and Jamaica all ethnic and religious communities participate in the event, locally known as "Hosay" or "Hussay". In Indonesia, the event is known as Tabuik (Minangkabau language) or Tabut (Indonesian).
Many of the male participants congregate together in public for ceremonial chest beating (matham) as a display of their devotion to Imam Husayn and in remembrance of his suffering. In some Shi'a societies, such as those in Bahrain, Pakistan, India, Afghanistan, Lebanon and Iraq, some male participants incorprate knives or razors swung upon chains into their matam.. This practice is permissible by major Usooli Ayatollah such as Muhammad Shirazi and Sistani, however some major scholars such as Khameini have banned it in Iran temporarily, while others such as Fadlallah deem it permanently impermissible. In general however, the act is controversial.'''
Around 1990s, after the post-first American-Iraq War, Iraq's Mehdi militia return to Iran for search Imam Mahdi.
Surely, there exists in the hearts of the Mu' mineen, with respect to the martyrdom of Husayn, a heat that never subsides.
O' Fatimah! Every eye shall be weeping on the Day of Judgment except the eye which has shed tears over the tragedy of Husayn for surely, that eye shall be laughing and shall be given the glad tidings of the bounties and comforts of Paradise.
Imam Ali ibn Hussein said:
Every Mu'min, whose eyes shed tears upon the killing of Husayn ibn' Ali and his companions, such that the tears roll down his cheeks, God shall accommodate him in the elevated rooms of paradise.
(Once when he happened to pass by Karbala), Isa Jesus sat down and began to weep. His disciples who were observing him, followed suit and began weeping too, but not comprehending the reason for this behaviour, they asked him: "O' Spirit of God! What is it that makes you weep?" Isa Jesus said: "Do you know what land this is?" The disciples replied: "No." He then said: "This is the land on which the son of the Prophet Ahmad shall be killed.