When a pronouncement by a religious scholar in Iran drove Iraq to the brink of civil war last month, there was only one man who could stop it: a 92-year-old Iraqi Shiite cleric who proved once again he is the most powerful man in his country.

Grand Ayatollah Ali al-Sistani said nothing in public about the unrest that erupted on Iraq¡¯s streets. But government officials and Shiite insiders say it was only al-Sistani¡¯s stance behind the scenes that halted a meltdown.

The story of Iraq¡¯s bloodiest week in nearly three years shows the limits of traditional politics in a country where the power to start and stop wars rests with clerics ¡ª many with ambiguous ties to Iran, the Shiite theocracy next door.