An incisive look at the past, present, and future of the religious divide that lies at the heart of the Middle East. At the heart of the Middle East, with its regional conflicts and proxy wars, is a 1400-year-old schism between Sunni and Shia. To understand this divide and its modern resonances, we need to revisit its origins--which go back to the death of the Prophet Muhammad in 632; the accidental coup that set aside the claims of...