TEL ASQOF, Iraq (Reuters) - A pickup truck races toward a burning village in northern Iraq, slamming to a halt behind an armored convoy that forms the only barrier between U.S. forces and Islamic State.

“We are fighting alongside our American brothers,” says the Kurdish fighter filming the scene, shouting to be heard over the sound of gunfire and explosions on the outskirts of Tel Asqof.

The clip, purportedly filmed on Tuesday during a fierce battle in which a U.S. Navy SEAL was killed, records the United States’ deepening involvement in the nearly two-year-old war against the jihadist militants.

Loath to become mired in another conflict overseas, the White House has insisted there will be no American “boots on the ground” in Iraq, instead deploying hundreds of troops to “advise and assist” local forces.

But footage of the firefight shown to Reuters by the Kurdish forces who filmed it, along with the accounts of others who took part, show how easily that distinction can blur.

One sequence shows U.S. and Kurdish forces sprinting through long grass from their initial position behind the vehicles toward a wall on the edge of the town. “Fucking run!” yells one of the Americans.

The exact circumstances of Petty Officer First Class Charles Keating’s death remain unclear. Kurdish officials say he was hit by a sniper and evacuated by helicopter within the hour, but died of his wounds.

He is the third U.S. serviceman killed in direct combat with Islamic State since a U.S.-led coalition launched a campaign in 2014 to “degrade and destroy” the insurgent group.

U.S. forces then withdrew, according to Kurdish fighters involved in the battle, leaving an armored Toyota Landcruiser by the side of the road, its tires flat.

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SIGNS OF BATTLE

The armor was not penetrated, but the outer shell of the vehicle bears the marks of an intense firefight: a hole punched through the door by a rocket-propelled grenade and shattered glass where bullets hit the windshield.

Spent casings were still strewn around the car on Wednesday when Reuters visited the village, 28 km (17 miles) north of Mosul. In the nearby grass lay an empty packet of bandages “for treatment of moderate hemhorrage”.

A U.S. military spokesman said Keating was part of a “quick reaction force” called in after American advisers got caught up in the firefight.

Kurdish fighters said a small team of five or six U.S. advisers had been stationed in Tel Asqof, often visiting the front line around 3.5 km (2.2 miles) away and assisting with reconnaissance and air strike coordination.

“It is the first time they fight with us on the ground,” said Wahid Kovali, the head of the force that battled alongside the Americans. “They were heroic.”

It was Islamic State’s largest attack in months against Kurdish peshmerga forces, who are considered the coalition’s most trusted and effective ally in Iraq and have cleared large areas in the north with the help of air strikes.

Close coordination with the coalition means Islamic State is rarely able to breach peshmerga defenses, which stretch several hundred kilometers in an arc around the north and east of Mosul - by far the largest city in the militants’ self-proclaimed caliphate.

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Early on Tuesday, however, the militants advanced from the village of Batnaya and blasted through the peshmerga positions, bringing a portable metal bridge to cross a defensive trench.

PICKUPS AND HUMVEES

From there they traversed open fields to Tel Asqof in a convoy including pickup trucks mounted with anti-aircraft guns, a bulldozer reinforced with metal plates and at least two Humvees, the charred remains of which could be seen inside the village.

“Daesh (Islamic State) came from here,” said a fighter named Adel, pointing down a street where flies converged on the splayed corpses of three militants.

Spreading out through Tel Asqof, the insurgents took up positions in houses, firing at the Americans on the outskirts of the village.

Craters in the asphalt mark where suicide bombers, some driving cars, blew themselves up as Kurdish forces closed in, eventually routing the militants.

Kurdish forces went house-to-house on Wednesday looking for any hold-outs and recovering their weapons and ammunition.

Back at a base, they laid out their haul, including machine guns, two explosive belts, four rocket-propelled grenades and several Kalashnikovs. There was also a small rucksack containing an unused roll of bandage and some dried figs.

One Kurdish fighter wore a digital watch taken from the wrist of a dead militant. “It’s a souvenir,” he said.

Saad, a peshmerga lieutenant who was wounded in the foot and still had a drip in the back of his hand, showed off an automatic rifle on which the previous owner had inscribed the name “Abu Khattab”. Stamped on the metal near the trigger was “Property of the U.S. government”.

At a press briefing on April 25, U.S. State Department spokesman John Kirby said the administration’s promises that there would be “no boots on the ground” in Iraq did not mean U.S. soldiers would never be involved in combat, only that there would be no “large-scale conventional ground combat operations”.

(This online version of this story was refiled to fix a typo in paragraph nine.)