BAGHDAD — As they patrol the streets of the troubled Shula neighborhood, the troops of Charlie Company seek out tormentors and guardians: Sunni Arab insurgents who come to kill in this largely Shiite Muslim enclave, and Shiite militiamen who protect residents while doing their killing in adjoining Sunni districts.
This is the sinister grid of today's Baghdad, a capital divided along sectarian lines and bearing little resemblance to the relatively tolerant metropolis it used to be.
On this morning, the American soldiers found no lurking killers, the enemy remaining in the shadows, well aware of the latest U.S.-led crackdown.
"It's too peaceful," said Lt. Col. Jeffrey Kelly, who heads the 1st Battalion of the 17th Infantry Regiment, which includes Charlie Company. "It's great. It's really nice talking to folks. It's really refreshing. I wish it would stay like that."
U.S. troops are again on the move in this city of 6 million people. Officials emphasize that the stakes are high in the new operation.
The U.S. offensive "will go a long ways toward determining the future of Iraq and the future of the Middle East," said Zalmay Khalilzad, the U.S. ambassador to Iraq, answering questions via e-mail. "The United States simply cannot achieve its goals of a democratic, stable and secure Iraq if the unacceptable levels of violence that we had in Baghdad in recent months continue."
About 8,000 additional U.S. troops have been in Baghdad since early August, accompanied by 3,000 Iraqi forces.
Despite an increase in violence in Baghdad and elsewhere in the last three days, U.S. officials say the early results of the Baghdad offensive seem encouraging.
The capital's homicide rate, which soared to a high of more than 1,800 killings in July, appears to have plummeted by more than half in recent weeks, the U.S. military says.
But the military's plan carries the same potential weakness as previous efforts: U.S. troops, backed by Iraqi allies, descend on an area in force, pacify it and move on, leaving peacekeeping duties to overwhelmed Iraqi police officers and soldiers.
In the past, the "we stand down, Iraqis step up" blueprint has failed because the Iraqis have proved unable to keep the peace, U.S. officials say. The Iraqi security services' inability to keep Iraqis from killing one another was what prompted the newly bolstered U.S. presence in Baghdad.
Officials acknowledge that there will never be enough U.S. forces in Baghdad to maintain a permanent presence in every neighborhood in the sprawling city and its perilous suburbs.
So what is different this time? U.S. and Iraqi officials say it's a matter of commitment.
The new campaign "is the most concentrated, focused effort to date in the capital, and the coalition military leadership and the Iraqi government are committed to not letting the city slip back into the vortex of violence," Khalilzad said.
Under the plan, each Iraqi brigade will be subjected to a three-day reassessment, said Army Maj. Gen. William B. Caldwell IV, the top U.S. military spokesman in Baghdad.
The plan also includes about $630 million in development funds for targeted neighborhoods.
In the new operation, troops typically cordon off neighborhoods and conduct door-to-door searches. House-sized assault vehicles equipped with automatic weapons and grenade-deflecting grates keep vigil on strategic corners, an imposing presence in urban battlegrounds turned eerily tranquil.
Iraqi forces are officially running the operation, but in the west Baghdad neighborhood of Shula one recent day, only three Iraqi soldiers accompanied Charlie Company on its six-hour sweep, often as observers.
So far, the U.S. military says, American and Iraqi forces have searched more than 33,000 buildings, including 25 mosques. But the yield has been relatively small. They have detained 70 suspects and seized more than 700 weapons and 19 arms caches, and they have cleared 10,200 tons of trash.
Commanders acknowledge that insurgents may be waiting out the U.S. presence, knowing the troops will soon move on.
"Could some individuals have fled the area? Of course," said Col. Michael Shields, commander of the Army's 172nd Stryker Brigade Combat Team. The Alaska-based unit's controversial four-month deployment extension was key to the Baghdad strategy.
"It's certainly a potential reality that many high-level leaders may have moved out of the area before the operation started," Shields said.
Thus far, residents, whatever their enmity toward U.S. forces, agree with American commanders that the troop presence has helped reduce violence.
"Unfortunately, we now prefer the foreigners protecting us rather than our brothers," said Kifah Khudhair, 38, an unemployed Sunni and former shop owner in the southern Baghdad neighborhood of Dora.
"Now there is an American patrol of two Humvees and they are controlling the area. In the past, there was an Iraqi patrol of 60 vehicles doing nothing but driving fast and blowing their horns."