Shiite cleric Muqtada al Sadr has returned to Iraq to the delight of hundreds of supporters after a self-imposed four-year exile in Iran.

Shiite cleric Muqtada al Sadr is known for heading Iraq's most feared militia, the Mahdi Army, which was responsible for widespread sectarian killings.  His death squads disbanded when he left the country in 2007. 

"I assume he is not going back to start standing up militias," Ryan Crocker, a former ambassador to Iraq, told USA Today.

"If he does, he's not going to last very long," Crocker said, adding the Iraq's Prime Minister Nouri al-Maliki would not allow it.
   
Al Sadr will be leading an organized political movement that will be a powerful player in al-Maliki's new government.  He is expected to demand that no U.S. troops remain past their scheduled withdrawal at the end of this year.