There was no resistance in the Shiite militia stronghold, but an ally of Muqtada al-Sadr protested the U.S. role.
BAGHDAD - U.S. and Iraqi troops poured into Baghdad's main Shiite militia stronghold of Sadr City yesterday, encountering no resistance but testing the Shiites' commitment to the U.S.-promoted campaign to drive insurgents from the capital.

The quiet but dramatic advance in Sadr City - involving nearly 1,200 U.S. and Iraqi forces who didn't fire a shot - marked one of the most significant developments in the security clampdown in Baghdad since it took effect nearly three weeks ago.

But it received the green light only after drawn-out talks between U.S. commanders and political allies of radical Shiite cleric Muqtada al-Sadr and his powerful Mahdi Army. Both sides are watching each other for any wrong moves on the same streets where they battled in the past, including intense urban warfare in 2004.

Sadr's militiamen lowered their profile under intense government pressure to give the security operation a chance to root out both Sunni and Shiite extremists. U.S. military leaders, however, must walk a fine line as part of the tacit truce. They are seeking suspected Shiite death-squad leaders, but must keep from squeezing Sadr's militia too hard - and risk collapsing the entire drive to reclaim Baghdad from extremists and gangs.

"The indication that we are getting is, a lot of the really bad folks have gone into hiding," Lt. Col. David Oclander said shortly after troops moved into Sadr City's teeming grid of low-rise buildings in northeast Baghdad.

Oclander said "not a shot was fired" as troops entered the area - which was constructed in the 1960s to house poor Shiites seeking work in the capital and which was known as Saddam City until the fall of former Iraqi leader Saddam Hussein in 2003. As the insurgency picked up steam in the last few years, Sadr City became the site of frequent battles.

Despite the calm as U.S. and Iraqi troops crossed into Sadr City, some Iraqis quickly protested the strong U.S. presence.

A Sadr ally, lawmaker Falah Hassan, claimed that the Sadr City pact called for Iraqi forces to lead the searches and only call in U.S. units if they faced resistance. He called the front-line U.S. role a "provocative act."

Sadr, too, has complained about the heavy U.S. role in the raids around the city. In a statement last week, he also decried the security plan's inability to stop car bombs and other attacks against Shiite civilians blamed on Sunni insurgent groups.

The comments raised worries that he could order his Mahdi Army to confront forces carrying out the security operation. But he didn't attempt to raise the stakes - a possible sign of newfound caution from Sadr.

Late last year, Washington strong-armed Shiite Prime Minister Nouri al-Maliki into pulling his protection for the firebrand cleric, who is based in the Shiite holy city of Najaf in southern Iraq and is a major political ally of the prime minister.

"We don't know if he has a change of heart, but certainly there is a change of tactic," the U.S. ambassador to Iraq, Zalmay Khalilzad, said on CNN's Late Edition.

For a third consecutive day, Baghdad was spared a car bombing or attack bringing mass casualties. But there was still bloodshed. A Shiite newspaper editor and a police officer were gunned down.

After nightfall, U.S. artillery was heard across Baghdad. In recent days, U.S. gunners have hit suspected Sunni insurgent staging grounds south of the city.

Around the capital, U.S. forces reported the discovery of a series of weapons caches.

On Other Fronts

Three U.S. troops were killed in combat in Iraq's western Anbar province, the military said yesterday. One Marine and one sailor died Friday, and another Marine was killed Saturday; their names were withheld pending family notification.

- Associated Press

British troopsand Iraqi forces stormed the offices of an Iraqi government intelligence agency

in the southern city

of Basra yesterday, and British officials said they discovered about 30 prisoners, some showing signs of torture.

Prime Minister Nouri al-Maliki, who derives major support from Shiite political groups, condemned the raid in Basra as an "illegal and irresponsible act." He said nothing about the evidence of torture.

The identities of the Basra detainees were unclear.

- N.Y. Times