Iraqi forces have made a crucial step in the bloody quest to retake Mosul from the Islamic State, according to a spokesman for the country's military. Iraqi Brig. Gen. Yahya Rasool announced that the city's university has been fully retaken from ISIS militants.

Special forces, known in Iraq as the Counter-Terrorism Service, or CTS, raised the Iraqi flag above the campus Friday, the Associated Press reports — but the troops were still days away from claiming complete control.

"Iraqi forces entered the university grounds Friday and managed to secure more than half of the campus the next day amid stiff resistance from IS militants, who mainly deployed sniper and mortar fire to slow down the advancing troops," the wire service adds Sunday.

Iraqi military launched its campaign to retake the northern city — the last major Iraqi city still in ISIS hands — last October. The former Iraqi commercial center is the place ISIS leader Abu Bakr al-Baghdadi first declared the caliphate, or Islamic state, shortly after the group captured it in June 2014. And it has been one of the central pillars of the militant group's diminishing territorial claims.

Earlier this month, Iraqi troops reached the Tigris River, which bisects the city, retaking much of Mosul's eastern half.

Yet, as Jane Arraf reports for NPR, the toughest fight is likely still to come. ISIS still holds the west side of the city, where more than 700,000 civilians are believed to remain.

Brig. Gen. Scott Efflandt, the deputy commander of U.S. forces in Iraq, tells Jane that part of the complexity of the fight ahead lies in the urban combat required:

"Picture any large metropolitan city on the U.S. East Coast — dense, older cities with smaller streets. And then picture having to eradicate all crime and any enemy force in there.

"It requires street by street, house by house, room by room operation. There's no quick way to do it. You have to walk, you have to climb stairs, you have to open doors and then repeat the process again and again and again and then when you're doing that you have to leave someone behind to guard the area you just went through. "

And they will continue to do so without the presence of American troops on the front lines.

For now, CTS spokesman Sabah al-Numan tells Reuters the special forces are combing the university's campus Sunday for remaining militants.

"The university is completely liberated and forces are sweeping the complex for any hiding militants," Numan said. "Most buildings are booby-trapped so we're being cautious."

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