Before Iraqi forces launch their highly anticipated offensive to retake the nation’s second-largest city, Mosul, back from the self-proclaimed Islamic State, they have one last battle ahead of them—reclaiming the Iraqi city of Hawijah from ISIS control, two defense officials told The Daily Beast.

Hawijah is one of the last ISIS bastions on the road toward Mosul, and in recent weeks the terror group has been unable to hold such cities under its grip, dedicating most of its resources to keeping Mosul instead, the officials said.

Hawijah, which at its peak had 450,000 residents, is a Sunni-dominated city that sits in the part of the Tigris River valley that Iraqi security forces initially bypassed in the push toward the city of Qayyarah, south of Mosul. In Qayyarah, the Iraqis set up a base where several hundred U.S. forces now are based, providing logistical support.

For months, ISIS has struggled to hold onto cities under its control, usually fighting for a time before fleeing to other cities. As a result, local forces have become increasingly confident in going after longtime ISIS-controlled cities.

With victory nearly certain, taking Hawijah will deprive ISIS of a place to flee to and give the Iraqi security forces a tactical and psychological win, the defense officials said.

“We can’t say for certain because it is up to the Iraqis, but it looks like that is where they are headed next,” one defense official explained to The Daily Beast. “It’s back clearing.”

Hawijah is just 50 miles east of the city of Shirqat, which Iraqi forces earlier this month wrestled from ISIS control in just a few days. Some ISIS fighters fled to Hawijah from Shirqat only to be killed—not by the Iraqis but by ISIS fighters disgusted that they fled, one defense official said.

“They lined them up and executed them,” the official said.

The U.S.-led coalition conducted airstrikes in support of Shirqat and is expected to do the same for Hawijah. Both Hawijah and Shirqat fell to ISIS control in 2014 and sit at a key juncture between two major oil-rich Iraqi cities, Kirkuk and Mosul.

The clearing of Hawijah would likely be complete just before U.S. military officials have signaled that all the troops needed for the operation for Mosul will be in place. The Pentagon on Wednesday announced the deployment of an additional 615 U.S. troops to support the battle for Mosul, adding they would arrive “in the coming weeks.”

And Marine Gen. Joseph Dunford, the chairman of the Joint Chiefs of Staff, has said U.S. training of Iraqi forces scheduled to take part in the Mosul operation would be done by mid-October.

Mosul fell under ISIS control June 10, 2014, when Iraqi forces fled from the ISIS fighters who marched through the city. Since then, Mosul has been the capital of the ISIS “caliphate” in Iraq, and U.S. officials have called Mosul “the final battle” to rid Iraq of the terror group.

According to the latest U.S. estimates, there are as many as 4,500 ISIS fighters in Mosul, and it will take as many as 12 Iraqi brigades, as well as an untold number of Iraqi police, Kurdish peshmerga forces, and Shiite-dominated militias, to reclaim the city.

The U.S. military, which is conducting nearly daily strikes on Mosul, said it is “prepping the battlefield for liberation,” Air Force Col. John Dorrian, the spokesman for the U.S.-led coalition, told reporters Thursday.

Defense officials have suggested the battle for Mosul would begin around early November.