Inside the air base where U.S. and Iraqi forces prepare to retake Mosul from ISIS

Retaking Mosul from ISIS

QAYYARAH, Iraq -- American forces are in Iraq again, and readying for battle.

Qayyarah Airfield, 40 miles south of Mosul, was ISIS territory just three months ago. Now recaptured, it’s a staging base run by the 101st Airborne Division.

U.S. general: Iraqi military is ready to take Mosul

They’re some of roughly 6,000 American service members in Iraq, five years after U.S. troops thought they had left the country for good.

Maj. Gen. Gary Volesky served in Mosul in 2009 after the U.S. invasion. Now he’s preparing to help Iraqi soldiers liberate the city from ISIS.

“We’re not shoulder to shoulder on the front lines. We’re enabling them. They are leading this fight,” Volesky said.

Unlike his earlier tour, he insists the American military is only here to advise, from a joint operation center, and not for combat.

Yet American service members are out there, very close to the action, and in some cases losing their lives.

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Lt. Col. Chris Payant CBS News

“This is a dangerous environment that we’re in,” Volesky said. “My number one priority is protecting all those service men and women that are there.”

Lt. Col. Chris Payant served two tours in Iraq after the U.S. invasion.

“I was a little surprised to be back here, but we are back at the invitation of the government,” Payant said.

At Qayyarah Airbase, he showed how ISIS destroyed the airstrip that Americans are rebuilding ahead of the offensive.

“Very methodically, very deliberately, from one end to the other, knocked down everything, destroyed everything possible,” he said.

The U.S. military is back in Iraq facing an enemy that’s losing territory, and more desperate than ever.

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American forces repairing a runway to be used in the battle for Mosul CBS News

If Isis can be defeated in Mosul, that will not end this country’s deep and violent religious divisions. Some Iraqis have said they want American troops to stay even after ISIS is gone, to help keep the peace.