'Shiite Giant' Extends Its Reach

The militias rapidly infiltrated key government agencies. Sadr's movement was not alone; it worked in parallel with another Shiite movement, the Supreme Council for the Islamic Revolution in Iraq, headed by Abdul Aziz Hakim.

Hakim's militia is known as the Badr Brigade. Its members largely took control of the Interior Ministry after the 2005 elections, building commando and other police forces. They are better organized and better armed than the Mahdi Army, thanks to decades of Iranian backing when it opposed Hussein. The Mahdi Army tended to supply the rank and file among Iraq's new police forces, rather than commanders. Together, the two Shiite militias infiltrated into Iraq's security forces thousands of people whose loyalty is to the religious parties rather than the national unity government.

In addition, Sadr's four ministries control 70,000 uniformed, armed men who are part of a government agency known as the Facilities Protection Service, according to the Interior Ministry. U.S. military commanders acknowledge that the agency has mushroomed to more than 140,000, largely outside American notice. A top former U.S. military commander has said militia fighters under the Facilities Protection Service are tied to kidnappings, execution-style killings and other crimes.

Both movements can also field thousands of armed civilian men in a matter of hours. Hakim, the leader of the Supreme Council, boasted to his followers in December that he could muster 200,000 militia fighters.

The Sadr movement claims more. "All Iraq is Mahdi Army," said Thamara al-Fetlawi, a civilian leader of the God's Martyrs Foundation, which cares for the families of slain and wounded Sadr militiamen as well as offering broader social services to followers of Sadr.

Fetlawi, like some other Sadr officials, rejected the definition of the Mahdi Army as a militia, apparently as a tactical move against any future efforts to disband the militias. Instead, he called it "the people's army," suggesting ordinary men who spontaneously grab their own weapons and respond when need and Shiite clerics call. The weapons seen by Washington Post reporters in Sadr City on the night of the Feb. 22 Samarra bombing included grenade launchers and heavy machine guns.

Sadr's Mahdi Army and the Supreme Council's Badr Brigade -- rivals that fought deadly battles in power struggles in the predominantly Shiite south last year -- cooperate when their interests overlap. In the turbulent days after the Samarra bombing, Sadr and Badr militiamen marched openly in a Shiite neighborhood of central Baghdad, each carrying banners declaring their battalion and brigade designations within their militias.

American officials have called the Shiite militias a danger to the Iraqi state. But the United States has yet to tackle what it and the Iraqi government say is their goal of dismantling the militias. In a congressionally mandated report last month, the State Department said that "a plan is being developed to assist Iraqi leaders" in breaking up the militias of the governing Shiite religious parties.

A more ominous warning came recently from the departing British ambassador to Iraq, William Patey, in a cable that was leaked. "If we are to avoid a descent into civil war and anarchy, then preventing the Jaish al-Mahdi from developing into a state within a state, as Hezbollah has done in Lebanon, will be a priority," Patey wrote, using the Arabic term for Mahdi Army.

'Claiming to Be the Mahdi Army'

Top U.S. officials and leaders of the Sadr movement both say many of the gunmen claiming to be in the Mahdi Army are increasingly operating outside Sadr's control. Nouri, Sadr's brother-in-law, and others blamed rogue elements and impostors for escalating killings and kidnappings since the Samarra bombing. Many of the attacks since July have focused on driving Sunnis from predominantly Shiite neighborhoods of Baghdad.

"I will say that evil exists in every sect and every place," Nouri said in the interview at his home in Najaf. "And also good exists. Just like with the Jews and the Christians, it is so in Islam.

"They might be gangs claiming to be the Mahdi Army and doing these bad things. But they don't believe in the doctrine, they only do what they want and wear clothes of the Mahdi Army. They do not follow the guidance of the leaders," Nouri said. "They are exposed when there are orders from the high command to sit and do nothing and still they do their acts. Anyone who is not following such orders from the Sadr office is not a member of the Mahdi Army."

"After the Samarra bombing, it seems there were major reprisals organized for large part in Sadr circles," said Hiltermann, of the International Crisis Group. "Moqtada himself was very clear no revenge should be taken. It's not clear whether he was simply not listened to, or was giving a double message -- one to the outside world, one to followers."

Unable to figure out Sadr's militia or approach him on political terms, Americans have been frustrated in their hopes of reining in the Mahdi Army, as well as the Badr Brigade.

"It would be a whole lot easier if these armed illegal groups had a coordinated structure with a clear headquarters," a Western diplomat in Baghdad said last month in response to questions about why no progress had been made on U.S. and Iraqi pledges to disband the militias. Ultimately, Hiltermann said, the Mahdi Army, as well as the Supreme Council and both groups' Sunni rivals, need only bide their time, until growing opposition to the war among the American public brings U.S. troops home.

"Then, the real struggle begins," Hiltermann said.

Correspondent Jonathan Finer in Najaf contributed to this report.

Tomorrow: The Mahdi Army's role in escalating sectarian violence.