Every year Iranians mourn the killing of Imam Hussein 14 centuries ago, as if it occurred last year to a personal friend. At the dawn of Islam, Hussein, grandson of the prophet and son of Ali, founder of the Shia sect, was massacred with 72 followers in the desert of Karbala. This war between two Arab factions for the control of the Umma, the nascent Muslim community, has become the founding moment of Shi'ism. This yearly ritual of Ashura strengthens the communal bond between Shias, a minority sect within Islam, throughout the world.

But lessons in modern history are to be drawn from Ashura....