Mr. Gordon, a New York Times military correspondent, is with Kurdish pesh merga forces on the northern approach to Mosul.
NEAR NAWARAN, Iraq — The sounds of battle north of Mosul on Thursday morning told the story of how Islamic State fighters had chosen to meet a new Kurdish assault: the eruptions of suicide car bombs and roadside mines.
Grim-faced, a group of Kurdish troops moved to meet the ambulances and gun-laden pickup trucks as they bore the casualties back from the fight at midday.
Blood stained the sand near their front-line aid station, and a medevac helicopter touched down on the highway back to Dohuk, ready to take the most grievously hurt to treatment there. One Kurdish fighter was so desperate to get his injured comrade through the snarl of military traffic that he began to fire shots into the air.
The third day of the campaign to drive the Islamic State out of Mosul was an expansion that included pushes on multiple fronts by American-trained Iraqi counterterrorism forces — which reached the town of Bartella less than 10 miles east of the city — and by the pesh merga. And for the first time, an American soldier numbered among the dead.
The Pentagon said that an American service member was killed in a bomb blast while supporting the Iraqi forces’ advance. It was the fourth time American service members have been killed in Iraq over the past year.
North of Mosul, thousands of Kurdish fighters were opening a new front, tasked with securing 27 villages and advancing in three main groups from the villages of Bashiqa, Narawan and Tel Iskuf.
Commanders said the Islamic State, also known as ISIS, ISIL or Daesh, were heavily contesting the assault, driving vehicle bombs at the Kurds and fighting for each village on the way.
“Daesh is still inside the villages, and they are going to resist more,” said one commander, Brig. Gen. Ismail Kamal. “They don’t have large numbers, but they are an ideological group and they aim to explode themselves and die. That’s our problem.”
Before dawn broke, the American air support began softening up the resistance. A United States Special Operations AC-130 gunship was circling overhead, and pounding blasts could be heard in the distance.
But there were also signs that the Islamic State had expected the assault.
One young Kurdish fighter said he had been in touch with residents in his hometown, Fazeliya, one of the villages the pesh merga intended to surround and then clear. Islamic State militants, he said, had sought to frighten the villagers from aiding the Kurdish assault by taking hostage 16 men whose relatives serve in the pesh merga. The hostages would be killed, the Islamic State had warned, it the pesh merga attacked.
Interactive Feature | Maps: The Advance on Mosul
As the Kurdish forces moved on a ridge overlooking the villages early in the morning, a sudden flurry of assault rifle fire broke out and quickly built up. It was an uncommonly intense fusillade, but it was not an ambush from below: It was the Kurds swinging their rifles skyward to blast a small Islamic State surveillance drone. After a minute, the aircraft came tumbling down.
After making a cut in the sand berm that served as the Kurds’ fortified border with Islamic State territory the past two years, a column of pesh merga tanks, armored vehicles and sport utility vehicles advanced. At first, the move was upbeat; several Kurdish soldiers were taking photographs of themselves on the ridge.
The Kurdish flag was raised in Nawaran, the first village, but resistance in the next town, Borima, was much stiffer. After several firefights, the Kurds called in a thunderous artillery barrage to try to ease the way.
In the distance, a bloodier drama was playing out. A couple of suicide car bombs hurtled toward the Kurdish fighters from Fazeliya. The pesh merga fired to disable them, but at least one of the trucks got close enough that its explosion wounded several pesh merga fighters, ripping the legs off one of them.
The Kurds said that they had intercepted communications in which Islamic State commanders were exhorting their fighters to resist to the death. Frequently, the militants were hiding until the pesh merga fighters entered a town to clear it, suddenly popping out of their sanctuaries to attack the Kurds with gunfire or possibly explosive belts.
Marveling at the Islamic State fighters’ seeming ability to emerge out of nowhere, some pesh merga wondered if they had dug tunnels that connected the villages.
For all that, the vast majority of the Kurdish casualties were the result of improvised explosive devices — the Americans call them I.E.D.’s, the Kurds say T.N.T.’s — and car bombs, commanders said.
The pesh merga did not officially release their list of casualties. But among pesh merga commanders and soldiers, word of the toll had spread: about a dozen pesh merga had been killed and many more wounded.
As the frustration with the operation mounted, one senior Kurdish official complained that the Americans had not provided nearly as many airstrikes as the pesh merga had expected, a criticism that may have reflected the need to simultaneously provide air cover for the Iraqi counterterrorism service assault. “We didn’t get anything like what we were promised,” said the Kurdish official, who was granted anonymity to discuss internal deliberations.
Col. John I. Dorrian, spokesman for the United States-led military coalition, insisted it would continue to cooperate with the Iraqis and the Kurds. “Coalition air power is certainly in demand, and we try to provide fires in a timely fashion when called upon,” he said. “Given the size and scope of the operation to liberate Mosul, there may be times when we are unable to fully meet the demand as quickly as forces on the ground would like.”
A photographer for The New York Times, Bryan Denton, was among those wounded when a vehicle bomb exploded near a unit of the Iraqi counterterrorism force east of Mosul on Thursday. He was taken to a hospital in Iraqi Kurdistan with cuts and bruises, and was in good condition.
Earlier in the day, the Iraqi prime minister, Haider al-Abadi, was optimistic about the offensive as he spoke by video link to a group of diplomats in Paris who were discussing the future of Mosul. He told the officials that the assault force — made up of Iraqi security forces, Shiite and Sunni militia fighters and Kurdish forces — was pushing toward Mosul “more quickly than we thought and more quickly than we had programmed.”
But on the battlefield, the pesh merga’s advance had slowed. General Kamal said that two or three more days would probably still be needed to clear the villages, but by evening, as the day’s toll was becoming clear, the mood among the pesh merga seemed more grimly determined than celebratory.
Follow Michael R. Gordon on Twitter@gordonnyt.
Kamil Kakol contributed reporting.