KALAK, Iraq -- Mounted machine-gun fire rattled in the distance as Kurdish soldiers in khaki and beige, and armed civilians in baggy pants, gathered Friday at a checkpoint that has become the newest frontline with extremist fighters seeking to conquer territory for their self-styled Islamic state.
Promises of U.S. help bolstered the hundreds of soldiers at the Khazer checkpoint near a town called Kalak, in the largely autonomous Kurdish region of northern Iraq, as militants from the Islamic State group crept closer to Irbil, the Kurdish capital just 23 miles (38 kilometers) away.
The Kurds have been northern Iraq's main line of defense against the al-Qaida breakaway group's rapid advance, though they are stretched over a long front.
Kurdish fighters, known as peshmerga, said they were prepared to die to defend their homeland -- many here seek outright independence from Iraq -- and said that U.S. strikes that began Friday had reassured them that Washington was not going to abandon them.
"I am not worried, because Obama said that Irbil is a red line," said a rosy-cheeked man who identified himself as Soran, a 28-year-old dual Iraqi-U.K. citizen.
The Americans delivered on their promise Friday, as U.S. armed drones and Navy fighter jets carried out two rounds of air strikes on Islamic State targets near Irbil. In the first, U.S. jets dropped 500-pound bombs on artillery. In the second, a convoy and two mortar positions were hit.
The Islamic State group had barreled down a two-lane road from its stronghold in the northern city of Mosul on Thursday, seizing Iraq's largest hydroelectric dam and taking control of enormous power and water resources and leverage over the Tigris River that runs through the heart of Baghdad.
The advance of the ultraconservative Sunni militants caused the flight of tens of thousands of Christians and the minority Yazidi community, who the extremists see as apostates deserving of death.
The Islamic State group's sudden advance came after they seized large parts of northern and western Iraq in June, including Mosul, Iraq's second-largest city.
The Kurdish checkpoint did not stop mortars from exploding inside the territory marked by it Friday. Soldiers were tired and stank of sweat, and many had been there for three days in 100-degree (40 Celsius) heat, patrolling and fighting.
The extremists mined the bridges too, making movement treacherous.
The threat of the Islamic State's fighters worsened after they seized massive amounts of new Iraqi army weapons abandoned by soldiers during the June assault, Kurds said.
By evening, the Kurdish fighters sat in a circle drinking water, eating thin pita bread. A few men snatched sleep atop large armored vehicles; others checked their phones.
Armed civilians were identified by their traditional Kurdish clothing: baggy high-waisted pants, held with wide sash belts. Some tucked pistols into their belts; they slung their rifles across their backs.
They included a grey-haired man guarding at the checkpoint, a two-lane stop-and-search point shielded by a large canopy. Further up the road, concrete pylons blocked the road.
Soran, who asked his family not be used, fearing he'd get in trouble with British authorities, was one of many men at the front line who said they were civilian fighters, underscoring a Kurdish mobilization to fight.
"I am defending my country," Soran said with defiance, though he shuddered when asked if he would approach closer to the Islamic State fighters.