Their mission has gone from all-out war five years ago to winning hearts and minds in a long, drawn-out counter-insurgency fight, CBS News chief foreign correspondent Lara Logan reports.
"We have to keep trying to build on what we've done, to hold what we've got," David Petraeus, Commanding General of the Multi-National Forces in Iraq said.
When U.S. soldiers flooded in under the surge, troop levels in the fifth year of the war reached their highest since the invasion.
And the violence slowly began to drop.
Largely because Petraeus encouraged deals with both Sunni and Shiite tribal militias - even those with American blood on their hands - to help the United States fight al Qaeda.
In response, attacks are down from just more than 2,000 a month last summer, to around 850 each month this year.
"On the one hand it's in a sense heartening to be hit with questions about jobs, about electricity, water or what have you, because it means they are not asking about security," he said.
Petraeus agreed that the political and the economic progress fall short of the security gains.
Basic services are still critically lacking. Before the war Baghdad residents got up to 24 hours of power a day; now they only get around seven.
"We never see any light in the end of the tunnel, it just looks like, just darkness," said University teacher Na'ail Zakarya.
Today, the streets of many Iraqi towns and cities are calmer - often because they're now divided. Ethnically cleansed during the fighting between the country's two main groups.
Even America's top commander in Iraq, Petraeus, is painfully aware that the gains in security in areas like this can easily be reversed.
His biggest worry: only a fraction of the 80,000 mostly Sunni fighters - or "Sons of Iraq" as the U.S. calls them - have been incorporated into the official security forces, held back by the mostly-Shiite government.
"It's been time-consuming; it's been frustrating. But some of that, I think, is understandable because what you're talking about is a government who has been asked to hire people who we're shooting at," Petraeus said.
The general warns that counter-insurgencies last on average 10 years, which means this war is only about halfway done - at best.
That will be of no comfort to about 2 million Iraqis who've fled the country, and nearly 3 million more who've been forced from their homes.
That's five years after the invasion ... that promised so much.