KHABARI CROSSING, Kuwait — As their convoy reached the barbed wire at the border crossing out of Iraq on Wednesday, the soldiers whooped and cheered. Then they scrambled out of their stifling hot armored vehicles, unfurled an American flag and posed for group photos.

For these troops of the 4th Stryker Brigade, 2nd Infantry Division, it was a moment of relief fraught with symbolism. Seven years and five months after the U.S.-led invasion, the last American combat brigade was leaving Iraq, well ahead of President Barack Obama's Aug. 31 deadline for ending U.S. combat operations there.

In a statement released by email, the president noted that the drawdown has been significant -- but isn't over yet:

Over the last 18 months, over 90,000 U.S. troops have left Iraq. By the end of this month, 50,000 troops will be serving in Iraq. As Iraqi Security Forces take responsibility for securing their country, our troops will move to an advise-and-assist role. And, consistent with our agreement with the Iraqi government, all of our troops will be out of Iraq by the end of next year. Meanwhile, we will continue to build a strong partnership with the Iraqi people with an increased civilian commitment and diplomatic effort.

P.J. Crowley, a spokesman for the State Department, told MSNBC that this is "an historic moment" that marks the end of Operation Iraqi Freedom, but not the end of the U.S. mission in Iraq. ___

EDITOR'S NOTE: The 4th Stryker Brigade, 2nd Infantry Division was officially designated the last combat brigade to leave Iraq under Obama's plan to end combat operations in Iraq by Aug. 31. Associated Press writer Rebecca Santana joined the troops on their final journey out of the country.

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When 18-year-old Spc. Luke Dill first rolled into Iraq as part of the U.S. invasion, his Humvee was so vulnerable to bombs that the troops lined its floor with flak jackets.

Now 25 and a staff sergeant after two tours of duty, he rode out of Iraq this week in a Stryker, an eight-wheeled behemoth encrusted with armor and add-ons to ward off grenades and other projectiles.

"It's something I'm going to be proud of for the rest of my life – the fact that I came in on the initial push and now I'm leaving with the last of the combat units," he said.

He remembered three straight days of mortar attacks outside the city of Najaf in 2003, so noisy that after the firing ended, the silence kept him awake at nights. He recalled the night skies over the northern city of Mosul being lit up by tracer bullets from almost every direction.

Now, waiting for him back in Olympia, Wash., is the "Big Boy" Harley-Davidson he purchased from one of the motorcycle company's dealerships at U.S. bases in Iraq – a vivid illustration of how embedded the American presence has become since the invasion of March 20, 2003.

That presence is far from over. Scatterings of combat troops still await departure, and some 50,000 will stay another year in what is designated as a noncombat role. They will carry weapons to defend themselves and accompany Iraqi troops on missions (but only if asked). Special forces will continue to help Iraqis hunt for terrorists.

So the U.S. death toll – at least 4,415 by Pentagon count as of Wednesday – may not yet be final.

The Stryker brigade, based in Joint Base Lewis-McChord in Washington state and named for the vehicle that delivers troops into and out of battle, has lost 34 troops in Iraq. It was at the forefront of many of the fiercest battles, including operations in eastern Baghdad and Diyala province, an epicenter of the insurgency, during "the surge" of 2007. It evacuated troops at the battle of Tarmiyah, an outpost where 28 out of 34 soldiers were wounded holding off insurgents.

Before the Aug. 31 deadline, about half the brigade's 4,000 soldiers flew out like most of the others leaving Iraq, but its leadership volunteered to have the remainder depart overland. That decision allowed the unit to keep 360 Strykers in the country for an extra three weeks.

U.S. commanders say it was the brigade's idea, not an order from on high. The intent was to keep additional firepower handy through the "period of angst" that followed Iraq's inconclusive March 7 election, said brigade chief, Col. John Norris.

It took months of preparation to move the troops and armor across more than 500 kilometers (300 miles) of desert highway through potentially hostile territory.

The Strykers left the Baghdad area in separate convoys over a four-day period, traveling at night because the U.S.-Iraq security pact – and security worries – limit troop movements by day.

Along the way, phalanxes of American military Humvees sat at overpasses, soldiers patrolled the highways for roadside bombs, and Apache attack helicopters circled overhead as the Strykers refueled alongside the highway.

Chief Warrant Officer 3 Gus McKinney, a brigade intelligence officer, acknowledged that moving the convoys overland put soldiers at risk, but said the danger was less than in past.

The biggest threat was roadside bombs planted by Shiite extremist groups who have a strong foothold in the south, McKinney said.

But except for camels straying into the road, and breakdowns that required some vehicles to be towed, there were no incidents.

The worst of the ride was conditions inside the Strykers – sitting for hours in a cramped space – and the temperatures outside that reached 50 Celsius (120 Fahrenheit).

The driver's compartment is called the "hellhole" because it sits over the engine and becomes almost unbearably hot. The vehicle commander and gunner can sit up in hatches to see the outside world. At the tail end are hatches for two gunners. Eight passengers – an infantry squad in combat conditions – can squeeze in the back.

Riding as a passenger felt a bit like being in a World War II-era submarine – a tight fit and no windows. The air conditioning was switched off to save fuel on the long ride south to Kuwait. Men dozed or listened to music on earphones.

When the convoy finally reached the sandy border, two soldiers, armed and helmeted, jumped off their vehicle and raced each other into Kuwait.

Once out of Iraq, there was still work to be done. Vehicles had to be stripped of ammunition and spare tires, and eventually washed and packed for shipment home.

Meanwhile, to the north, insurgents kept up a relentless campaign against the country's institutions and security forces, killing five Iraqi government employees in roadside bombings and other attacks Wednesday. Coming a day after a suicide bomber killed 61 army recruits in central Baghdad, the latest violence highlighted the shaky reality left by the departing U.S. combat force and five months of stalemate over forming Iraq's next government.

For Dill, who reached Kuwait with an earlier convoy, the withdrawal engendered feelings of relief. His mission – to get his squad safely out of Iraq – was accomplished.

Standing alongside a hulking Stryker, his shirt stained with sweat, he acknowledged the men who weren't there to experience the day with him.

"I know that to my brothers in arms who fought and died, this day would probably mean a lot, to finally see us getting out of here," he said.