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.