During decades of turmoil, war, and regime change in Iraq, one influential figure has loomed above all others: Grand Ayatollah Ali al-Sistani. As the revered senior Shia cleric in a Shia-majority country, Sistani commands the loyalty of millions of faithful. With quiet authority, Sistani has tried from behind the scenes to steer Iraq through a series of existential crises since the U.S. invasion and fall of Saddam Hussein's regime...