In Afghanistan, dozens of Shiite Muslim worshippers were killed and dozens more injured when a suicide bomber detonated explosives at a crowded mosque in Kabul. Militants affiliated with ISIS claimed responsibility. In many parts of the world, Shia and Sunni Muslims have been locked in bloody conflicts for centuries. This attack came as Shiites were marking the end of the 40-day period when they grieve the death of the Prophet Muhammad’s grandson, who was killed in the year 680 by rival Muslims.