The two powers of the Middle East, Iran and Saudi Arabia, are in the midst of a diplomatic row with roots that go back more than 1,300 years.

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Ali was assassinated in 661AD as a civil war in Islam brewed. This disagreement culminated in the battle of Karbala—in modern day Iraq—where Sunni rulers killed Mohammed’s grandson Hussein in 681AD.Geneive Abdo, a fellow at policy institute Stimson Center’s Middle East program, tells Quartz “the tragedy of Karbala and their act of human suffering and martyrdom has been the narrative that Shias have lived by for many years.”

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