BAGHDAD -- Some 10,000 Iraqi troops fanned out in Baghdad's Sadr City on Tuesday, taking positions on main roads, rooftops and near hospitals in an attempt to establish government control in the Shiite militia enclave for the first time since Saddam Hussein's ouster.
Success relies on whether a truce holds with fighters loyal to anti-U.S. Shiite cleric Muqtada al-Sadr.
The large force, in tanks and Humvees and on foot, met no resistance from al-Sadr's Mahdi Army militia as it rolled into the sprawling district.
The Iraqi soldiers and police passed burned-out shops and buildings pockmarked with bullet holes, signs of years of clashes. But many stores were open, and some residents came out to greet them. Some Mahdi Army fighters passed out copies of the Quran to the soldiers as a sign of good will.
It was a stark contrast to a government offensive against Shiite militias in the southern city of Basra launched in late March. That assault sparked a wave of Mahdi Army violence across the south and in Sadr City. Fighting in the south was eased by a cease-fire deal in mid-April, brokered by Iran, which has ties to both al-Sadr and the government.
Tuesday's deployment was paved by a separate truce reached last week.
Under the deal, militiamen promise not to attack residential areas or the Green Zone, but they refuse to give up their light weapons. Iraqi forces promised to try to refrain from seeking American help to restore order. U.S. military officials said they would follow the Iraqis' lead, and no American forces were involved in Tuesday's deployment.
The move, code-named "Operation Peace," is the latest by Prime Minister Nouri al-Maliki to impose government authority in areas controlled by armed groups. Besides the Basra offensive, an ongoing sweep launched a week ago in the northern city of Mosul aims to uproot al-Qaida in Iraq and other Sunni insurgents.
But the fragile truce's survival could depend on how forcefully the troops try to reduce the Mahdi Army's long-unquestioned domination of Sadr City, home to 2 million Shiites.
Already, al-Sadr supporters were complaining of the heavy deployment.
"We were surprised by the size of the force," Sheik Salman al-Freiji, director of the Sadr Movement office in the district, told The Associated Press. "But their entry in such size has sparked fears that there could be violations of mosques and homes. There must be respect."
"We are attempting to maintain restraint, so there is no retaliation," al-Freiji said. "This force is bigger than we expected, with tanks, and it could be a provocation."
The next stages of the operation, which includes plans to arrest some militia suspects, could indeed spark retaliation. In the past, some rogue Mahdi Army fighters have continued violence even after the leaders have called for a halt.
Iraqi commanders also intend to search for heavy weapons such as large mortars, rockets and ordnance that could be used in roadside bombs -- though not lighter weapons. The Mahdi Army claims it does not have any heavy weapons in Sadr City.
There is also the danger that Shiite fighters could move elsewhere in Baghdad to operate. Iraqi troops found a large weapons cache Monday on the grounds of a mosque in the Shaab district, neighboring Sadr City, the U.S. military said. The find included eight armor-piercing roadside bombs known as explosively formed penetrators, or EFPs, which the U.S. claims Iran provides to Shiite militants for attacks on Americans. Iran denies the claim.
Throughout the day, the Iraqi force spread out across most of Sadr City, a 12-square-mile grid of avenues laid over a maze of tiny alleys forming densely populated slums.
The troops set up checkpoints on main roads, took positions on rooftops and near hospitals and began Humvee patrols. A tank was stationed about 20 yards from the main Sadr Movement office, with a checkpoint about 100 yards away.
"The government chose the approach of preventing bloodshed, and entered the city to coordinate with the representatives of the Sadr movement," Iraqi military spokesman Brig. Gen. Qassim al-Moussawi told reporters.
It was the most widespread Iraqi military presence in Sadr City in years. The district in northeast Baghdad fell under the control of al-Sadr soon after the 2003 fall of Saddam -- when the district was renamed from Saddam City to Sadr City, after Muqtada al-Sadr's father, a revered cleric who was assassinated in 1999.
The district erupted into major violence during two nationwide revolts by the al-Sadr movement in 2004, and has been a constant scene of clashes between militiamen and allied Iraqi and U.S. troops.
Coalition forces have made several attempts of a lesser scale to rein in the militia there. Iraqi police have always had a small presence in the district, but they have largely been cowed by the better-armed black-garbed Mahdi Army fighters who operated freely.
During the Basra sweep in late March and early April, Sadr City erupted again, with barrages of mortar attacks on the Green Zone and heavy clashes with U.S. troops, who moved into the district's southernmost section. The Americans have been erecting a nearly complete concrete wall between their position and the rest of Sadr City.
Success in Sadr City would be a significant boost for al-Maliki's attempts to extend government authority -- and for the Iraqi security forces, which have struggled to overcome sectarian divisions. During the wave of violence sparked by the Basra offensive, some Iraqi security units refused to fight the militias because of intimidation or loyalties to al-Sadr.