Shiite Muslims across the world marked Ashoura on Thursday, a holy day symbolizing sacrifice and martyrdom.Ashoura commemorates the martyrdom of Imam Hussein, grandson of the Prophet Muhammad, at the Battle of Karbala in A.D. 680. Imam Hussein was killed with his family and companions after refusing to pledge allegiance to the Umayyad caliphate.The event cemented the schism between Sunni and Shiite Islam and remains a powerful symbol of resistance against oppression and injustice.In Karbala, the southern Iraqi city holy to Shiite Muslims, security was tightened as visitors arrived.Religious banners flew from the walls of Imam Hussein’s golden-domed shrine and actors played out scenes from the 7th century.