... But 50,000 U.S. troops will remain in the country in an advisory capacity
The last U.S. combat brigade has withdrawn from Iraq, more than seven years after the U.S.-led coalition invaded the country in a war that has claimed the lives of more than 4,000 U.S. troops.
The brigade left the country in the early hours of Thursday morning, two weeks before an August 31 deadline for the end of Operation Iraqi Freedom pledged by Barack Obama, the U.S. president, on taking office.
A U.S. soldier of the 1st Battalion, 116th Infantry Regiment carries his luggage as he prepares to pull out of Iraq at Tallil Air Base near Nassiriya, 300 km (185 miles) southeast of Baghdad, August 15, 2010. Iraq signed a bilateral security agreement in 2008 that paves the way for a full U.S. withdrawal by the end of 2011. Picture taken August 15, 2010.
"The last one crossed [the border] at about 6:00 a.m. this morning," Lieutenant Colonel Eric Bloom said on Thursday.
"They have a few more days to clean the equipment, prepare the equipment, get it ready for shipment and then they'll fly out [to the U.S.]."
The withdrawal brings to an end a controversial and bloody operation that began with the American "shock and awe" bombing campaign of Baghdad in March 2003, and saw the U.S. military endure some of the heaviest fighting it had seen for a generation.
About 50,000 U.S. troops will remain in the country in an advisory capacity, helping to train Iraqi forces in a new mission codenamed Operation New Dawn, which will run until the end of 2011.
Al Jazeera's Rawya Rageh, reporting from Baghdad, said there is now a shift to acting as "advise-and-assist" brigades which "consists mainly of training and providing logistical support."
"They will, however, have the right to defend themselves against attacks if they are targeted," she said.
"But they will not be stepping in, they will not be conducting any military operations per se, unless they are specifically called on to do so by the Iraqi government."
Philip Crowley, the U.S. state department spokesman, called the end of combat operations a "historic moment," but stressed America's long-term commitment to Iraq was unwavering.
"We're not ending our involvement in Iraq," he told U.S. broadcaster MSNBC.
"We will have important work to do. This is a transition. This is not the end of something. It's a transition to something different. We have a long-term commitment to Iraq."
The Iraqi military is using U.S. equipment, which means security forces will need U.S. trainers, technicians and links with the U.S. military industrial complex in years to come.
Obama had made ending the Iraq war a central policy of his presidential campaign, and after taking office he immediately announced plans to bring combat troops home by the end of August this year.
He inherited around 144,000 troops in Iraq, 30,000 fewer than the peak levels of 2007, when the administration of George Bush ordered a so-called surge in an effort to improve Iraq's atrocious security situation.
After becoming president, Obama immediately set about transferring responsibility for security from the U.S. military to Iraqi forces, gradually pulling U.S. troops out of the country.
Generals approved the final tranche of the drawdown in May this year, despite a rise in violence following inconclusive parliamentary elections in March.
But while the end of combat operations will be welcomed by many ordinary Iraqis, U.S. troops leave behind a country with a far from certain future.
Tahseen al-Sheikhly, a spokesman for the Baghdad Security Plan, a joint coalition-Iraqi body aimed at reducing violence, described the security situation as "under control," but said the government's fight against al-Qaeda will go on for yet another year or two.
"The political instability reflects negatively on the security situation," he said.
"But at the same time our security forces work under the command of Baghdad and I think they are professional and not affected by the political situation.
"Al-Qaeda and their allies are trying to use this situation [of political instability] to stage attacks against the security forces, just to send the message that if there is an American withdrawal, the Iraqi forces are not able to protect the people."
Concerns have been raised that the U.S. is pulling out of the country too soon, most notably by Lt Gen Babaker Zebari, Iraq's most-senior army officer, who warned last weekthat his forces would not be ready to take control of security until 2020.
Zebari predicted that "problems will start after 2011," referring to the Obama administration's deadline for the full withdrawal of U.S. troops from Iraq.
In a graphic illustration of his point, a blast this week at an army recruitment center in Baghdad left at least 60 people dead and more than 100 wounded, in one of the worst attacks to hit Iraq for months.
But Crispian Cuss, a former British army officer in Basra and now a security analyst with the Olive Group in London, told Al Jazeera that the Iraqi security forces had done an "extraordinary job" in the last couple of years despite a lot of challenges.
"You've seen them take over security of regions one by one you've seen them take over security of their cities since June 2009," he said.
"Yes, it's not as tidy as when the Americans were in charge, yes, they're not as effective, in particular the police, yes, there's incidence of corruption, and yes there are these tragic one-off mass casualty events.
"But the fact is, they've done a good job. The country hasn't been destabilized in the last 14 months and the security situation, bit by bit, improves."
The Iraqi government acknowledged on Thursday that with the troop withdrawal, the time has come to take responsibility for their own security.
"I think we have to do the job by ourselves, at the end we should be fully responsible for our security," Ali al-Dabbagh, the Iraqi government spokesman, told Al Jazeera.
"Although it looks as if we have many threats and challenges for us here in Iraq, at the end we have to balance whether we have to accept foreign troops for a long period or [if] we have to do the job ourselves. We have to choose to do the job by ourselves.
"Of course, this is ahead of the schedule adopted by the withdrawal agreement between us. But this is part of the responsible withdrawal President Barack Obama had promised his people," he said.
The war, which began when a U.S.-led coalition invaded Iraq in 2003 and overthrew the government of Saddam Hussein, has proven costly to America both in terms of dollars and human life. Operation Iraqi Freedom has cost more than $900 billion and seen 4,415 U.S. troops die.
That figure has been dwarfed by the number of Iraqi civilians killed, estimated at more than 100,000, according to the Iraq Body Count website.
At the height of the violence in 2006, Iraq was brought to the brink of all-out civil war between the Sunni and Shi'a communities, with bombings and sectarian murders becoming a deadly part of day-to-day life in many parts of the country.
In 2007, President Bush ordered a controversial surge of more than 30,000 combat troops in an effort to improve the situation.
That, combined with improved co-operation with Iraq's Sunni population, led to a substantial improvement in security that allowed U.S. troops to begin transferring responsibility to Iraqi forces.
Al Jazeera and agencies