While Sunni Muslims also commemorate the Ashura - the 10th of Muharram in Islamic calendar - for Shiites, the murder of Hussein and his family by the army of the Ummayad Caliph Yazid marks the formal split from the religious establishment. Every year, Shiites (the followers of Ali – cousin of Islam's prophet Muhammad and Hussein's father) relive the battle of Karbala and mourn Hussein's death.

Shiites, and many Sunnis also, regard Hussein as a symbol of "peaceful resistance" against Yazid's "tyrannical rule." The prophet's grandson refused to pledge allegiance to Yazid, which resulted in a battle in Karbala, located southwest of Baghdad. Shiites around the world commence the first month in Islamic calendar, Muharram, by holding processions and enacting episodes from the historic battle.

Self-flagellation, including the beating of the chest and walking barefoot on fire, are among the Ashura rituals. Liberal Muslims criticize the use of daggers and "self-torture" as regressive symbols that have no connection with the modern world. For devout Shiites, it is their way of feeling the pain that Hussein and his family had to bear during the Battle of Karbala.

Since the Iranian revolution in 1979, Shiite Islam, as well as events like the Ashura, have taken on an anti-West and anti-US posture. Ayatollah Khomeini, the founder of the theocratic Iran, used Karbala as a political symbol against imperialism. After the revolution, Tehran actively promoted its version of Shiite Islam to other Muslim countries, including Afghanistan and Pakistan.

For Shiites in the Middle Eastern countries under Iran's influence, the Ashura commemorations are a political statement against Saudi Arabia, which endorses a hardline Wahhabi Islam. For Sunnis who toe Riyadh's line, the Ashura rituals are "un-Islamic." For Sunni militants active in the Middle East, and groups like the Taliban in Afghanistan and Pakistan, Shiites are apostates.

Sunni extremists in Afghanistan have repeatedly targeted Hazara Shiites, a peaceful minority community. In July 2016, at least 80 people were killed in an attack on Shiite Hazaras in Kabul. The "Islamic State" (IS) militant group claimed responsibility for the attack. Islamist groups regularly attack Shiites in neighboring Pakistan also.

Traditionally, Shiites in Pakistan have been closer to a mystical version of Indian Islam, but in the past few decades, the Iranian influence has caused a radical transformation. Political analysts say Iran-backed Shiite extremists groups are also active in the South Asian country.

Although the Ashura is a religious event, Pakistani authorities beef up security around the Shiite processions. Banned militant organizations have bombed the Ashura rallies in the past. The security is also tight in other Sunni-majority countries during this time.