Sunni Saudi Arabia and Shia Iran, once allies and twin pillars of US strategy in the region, became mortal enemies after 1979. Ghattas weaves together history, geopolitics, and culture to show how the 1979 Iranian revolution-- fueled by American policy-- fed intolerance, suppressed cultural expression, and encouraged sectarian violence from Egypt to Pakistan, leading to the assassination of countless intellectuals, the birth of groups like Hezbollah in Lebanon, the September 11th terrorist attacks, and the rise of ISIS.