U.S. commanders in Iraq have identified up to a dozen Iraqi army brigades that could mount an attack on Mosul and potentially need U.S. combat advisers at brigade-level headquarters, a top American general in Iraq said Tuesday.
Iraqi commanders and their U.S. advisers are also debating whether the primary invasion force for the Islamic State group's stronghold should come from the Iraqi-controlled south or from the Kurdish region in the north and east — or maybe both, the general said.
The remarks from Army Maj. Gen. Richard Clarke, the head of U.S. land forces in Iraq, are the latest from top American officials that bring into focus the upcoming battle of Mosul and the role U.S. troops might play.
"The Iraqis clearly are seeing, you know, somewhere in the neighborhood I would estimate between eight and 12 brigades that could be part of the Mosul counterattack," Clarke told reporters Tuesday in a video teleconference from his headquarters in Baghdad.
"As they continue to do their estimates, we're going right along with them," Clarke said.
It remains unclear when the Iraqis might launch an attack on Mosul, which Islamic State militants have controlled for almost two years.
The U.S. has signaled a willingness to provide ground-level combat advisers for Iraqi brigades and also attack helicopters for close-air support in urban terrain. But a key question remains whether the Iraqi government will ultimately request that expanded U.S. support, which is fiercely opposed by some factions of the Shiite-led government in Baghdad.
There are about 3,800 U.S. troops authorized for Iraq.
Clarke said U.S. officials have daily meetings with Iraqi generals about planning for Mosul.
"Everything that we do will be through the — with the approval of the — government of Iraq. ... I think that still remains to be seen, what exact capabilities will be needed. It really goes to what the Iraqis need and when," Clarke said.
"If they do this on their own, it will be a more longer lasting, you know, win for the future of Iraq," Clarke said.
The key question for the Iraqis' battle plan will be determining the best approach for the primary invasion force, whether to come from Mosul's south or from the Kurdish region to the city's north and east, Clarke said.
Both options carry risks. Coming from the south is difficult because Islamic State militants control about 100 miles of terrain along the Tigris River, which the Iraqi force would need as a primary supply line linking Mosul to Baghdad.
Coming from the Kurdish region is fraught with political problems because the autonomous regional government may not want to stage brigade-size units from the mostly Shiite Arab Iraqi force. And the Kurdish peshmerga fighters themselves are reluctant to serve as a primary invasion force due to ethnic tensions with Mosul's Sunni Arab population.
"It goes to the operational construct of how the Iraqis may do this," Clarke said. "Because they could go completely to the Kurdistan region and be right on the footsteps of Mosul. Or they could go up through Bayji, up what we call Highway One, almost due north. And what this gives them are multiple options.
"Or they could use a combination of both," Clarke said.
Many top U.S. military officials have suggested the Kurds' mission will be limited to "blocking" the Islamic State militants from any retreat in the direction of the Kurdish region.
American officials expect at least two peshmerga brigades to join in operations in Mosul.
The U.S. and Iraqis appear to be pushing troops toward Mosul. The Iraqi army is amassing combat units and the U.S. has stood up a train-advise-and-assist team at a division-level Iraqi operations center in the village of Makhmour, about 60 miles southeast of Mosul.
Known as the Nineveh Operations Center, the facility in Makhmour is along the edge of Kurdish-controlled territory near the ISIS-held Tigris River valley and will be a primary base for the U.S. to support the Mosul operations.
Clarke declined to say how many Iraqi troops are at the Makhmour facility. Iraqi government officials have suggested it will be about 4,500.
It is a "tactical assembly area" and the Iraqi forces are there "to posture for future operations," Clarke said.
Clarke's comments suggest that the U.S. military believes the Iraqi force, which collapsed in 2014 as Islamic State militants seized major cities, has grown to a size sufficient for a Mosul operation.
In January, a defense official said the fight in Mosul will need "roughly 10 brigades" for a total force of between 20,000 and 30,000.
The total Iraqi force that has undergone American-led training recently is reaching that size. About 16,000 Iraqi Security Forces and about 4,000 Kurdish peshmerga fighters have been trained, Clarke said.
The U.S. military is now shipping two brigade-size equipment sets to the Peshmerga, providing enough weapons, vehicles and support gear to outfit about 4,400 Kurdish troops.
"That equipment is arriving now," Clarke said.