The last American combat brigade pulled out of Iraq and crossed into Kuwait at dawn on Thursday, almost seven and a half years after the US-led invasion ousted Saddam Hussein, a US military spokesman said.
The 4th Stryker Brigade, 2nd Infantry Division, crossed the border with the neighbouring Gulf emirate at about 6:00 am (03:00 GMT), ahead of the planned declaration of an end to combat operations at the end of the month.
The pullout came two days after a suicide bomber killed 59 people at a Baghdad army recruitment centre in Iraq's deadliest attack this year, sparking concern the country's forces are incapable of handling security on their own.
"Yes, they did," Lieutenant Colonel Eric Bloom told AFP, confirming US media reports that the 4th Stryker Brigade had crossed into Kuwait. "The last one crossed at about 6:00 am this morning."
It took three days for the 360 military vehicles and 1,800 soldiers to get down the road from Baghdad, through the Shiite south and into Kuwait, according to The Los Angeles Times.
Bloom said about 56,000 US soldiers remained stationed in Iraq, with that figure set to drop to 50,000 by September 1, less than a third of the peak figure during "the surge" of 2007.
At that point, the US mission in Iraq will be re-christened "Operation New Dawn", from "Operation Iraqi Freedom" -- the name given to American operations here since the 2003 invasion.
"And we'll continue to go through our responsible drawdown to meet that drawdown by 1 September," Major General Stephen Lanza said in an interview with US television channel MSNBC. "It is about a transition to a change of mission, going from combat operations to stability operations."
In a letter dated August 18 and posted on the White House website, President Barack Obama hailed the end of combat operations but made no mention of the final combat troops leaving.
"Shortly after taking office, I put forward a plan to end the war in Iraq responsibly," the letter said.
"Today, I'm pleased to report that -- thanks to the extraordinary service of our troops and civilians in Iraq -- our combat mission will end this month, and we will complete a substantial drawdown of our troops."
All US troops are supposed to leave the country by the end of next year, according to the terms of a bilateral security pact, and Obama has insisted the ongoing withdrawal is on schedule and will not be altered.