ESKI MOSUL, Iraq — An unarmed Sunni Arab man walked along a road in a patch of northern Iraq newly liberated from Islamic State extremists, holding a white surrender flag — a signal to Kurdish fighters that he is not a militant. Cars drove by, a similar white banner flying from their windows.

As they retake territory from Islamic State militants, Iraqi Kurdish fighters have found surprising ambivalence in areas they freed from the jihadis’ oppressive rule. Locals have swiftly shaken off the imposed Islamic lifestyle — but as Sunnis, from the same ethnic group as the militants, many are nonetheless bracing for treatment as collaborators.

For their part, the Kurdish peshmerga troops are suspicious about why the locals chose to stay on when the Islamic State conquered the area in a blitz last year. An Associated Press team travelling with the Kurds found the road to Mosul, a coveted prize in the battle for Iraq, strewn with suspicion and fear.

The recent Kurdish push secured several towns and villages along a critical junction that connects the town of Tal Afar to the city of Mosul — two of the IS group’s biggest strongholds in Iraq. The artery, which eventually leads to Syria, has been a vital supply line for militants transporting weapons, goods and people across the lawless Iraq-Syria border.

The Kurdish fighters struggled for months to inch ahead, backed by U.S.-led coalition airstrikes. On Tuesday, at least four airstrikes hit IS positions near Eski Mosul, a village of up to about 9,000 residents some 40 kilometers (25 miles) northwest of Mosul.

Kurdish Brig. Gen. Bahjat Taymes, who led the peshmerga operation to retake the Tal Afar-Mosul junction, said seizing it was “crucial” because it also leads to the Mosul Dam, which Kurdish and Iraqi forces won back in August with the help of U.S. airstrikes.

Last week’s uptick in the airstrikes marked the start of a new, broader effort to disrupt Islamic State’s supply lines ahead of an expected operation later this year to take back Mosul, U.S. military officials said.

A senior U.S. military official said military leaders were watching to see how Islamic State militants respond as their supply and communications lines dry up. The official spoke on condition of anonymity because he was not authorized to discuss the operations.

Islamic State fighters destroyed many power lines and bridges trying to slow the Kurdish advance but were eventually routed from the area. In the nearby town of Shandoukhah, bulldozers and Kurdish troops worked feverishly this week to enforce positions, piling up dirt and sandbags as deterrents against suicide bombers or shelling.

“Before we proceed further, we have to secure our backs,” Kurdish Col. Marwan al-Mizouri told the AP.