One week into the battle for Mosul, U.S. troops are embedded with Iraqi battalion- and brigade-level units, pushing forward with mobile headquarters elements as the fight moves toward the dense city center, according to U.S. officials familiar with the operation.
The American and Iraqi troops face an increasingly complex fight as some Islamic State fighters remain behind the advancing forces to mount guerilla-style attacks from the rear, according to U.S. officials who spoke on condition of anonymity
Behind the front lines, a massive fire spewing toxic sulfur fumes is posing a health threat to U.S. forces deployed to a logistics base south of Mosul, prompting some U.S. commanders to order troops to wear gas masks when outdoors, officials said.
American special operations teams totaling up to 200 troops are assigned to 12 Iraqi brigades pushing toward Mosul. They're moving with multiple battalion-level headquarters, Kurdish Peshmerga units and elements of the Iraqi Counter Terrorism Service, the elite force that operates independently from Iraq's army, the officials said.
The U.S. officials say American troops are not involved in direct combat. Instead, they are providing tactical advice and up-to-the-minute intelligence, coordinating U.S. airstrikes and close-air support for advancing Iraqi troops and offering logistical support.
The Mosul operation will be the biggest test to date for the Obama Administration’s strategy of deploying small teams of combat advisers while trying to keep them behind the forward-most fighting positions and out of harm's way. Chief Petty Officer Jason "JJ" Finan was killed outside Mosul on Thursday when his Humvee struck an improvised explosive device during a mission in support of some Navy SEALs. Finan, an explosives disposal technician, was the fourth U.S. combat fatality since U.S. troops returned to Iraq in 2014.
In the week since the Mosul operation began on Oct. 17, the city's residents have not fled the city in large numbers or launched any grassroots uprisings that threaten to undermine the Islamic State group's control there, government officials said. Mosul, Iraq's second-largest city, has more than a million residents and the civilians' response to the fighting is a top concern for U.S. and Iraqi forces.
The American and Iraqi forces pushing toward Mosul are within range of the indirect fire positions erected by the Islamic State group, also known as ISIS or ISIL. But the U.S. and Iraqi forces have not yet encountered the dense urban terrain that will likely include house-to-house fighting and house-borne improvised explosive devices, the U.S. officials said.
U.S. officials say seizing the city that ISIS has controlled for more than two years may take weeks or months.
U.S pilots are flying over the front lines in Apache H-64 attack helicopters, which provide close-air support, gather battlefield intelligence and boost the morale and confidence of ground-level Iraqi forces, U.S. officials said.
The U.S. and Iraqi forces are attacking Mosul along several primary axes. In the east, the forces have reached the town of Bartella, about 10 miles east of Mosul, probably the closest those Iraqis have gotten to the city. To the northeast, Iraqi troops are fighting on Bashiqa, about 25 miles from Mosul's city center. And to the north, Iraqi forces are fighting in Tal Keppe, 10 miles from the Mosul's outskirts.
The city is not completely surrounded. ISIS continues to control routes into and out of western Mosul, allowing ISIS fighters to resupply and bring fighters in from other parts of its territory in Iraq and Syria, U.S. officials said.
Further from the front, larger cadres of U.S. personnel are supporting the operation from more permanent military bases in Irbil, Makhmour and at the airfield at Qayyarah West. A total of about 5,000 U.S. troops are deployed to Iraq.
Qayyarah West is about 40 miles south of Mosul and the U.S. military is working to upgrade the damaged airfield there to accommodate heavy-lift U.S. aircraft and allow it to grow as a major logistics hub for the Mosul operation, officials said.
The several hundred U.S. troops at Qayyarah West have been exposed to smoke from a sulfur mine in nearby Mishraq, which ISIS fighters on Saturday set ablaze in an effort to slow the invasion operations.
The wind has blown dangerous fumes toward the U.S. troops. "It is toxic. Though, in the concentrations we are seeing, nothing we would consider lethal," Navy Capt. Jeff Davis, a Pentagon spokesman, said Monday.
The smoke has forced some U.S. troops to use the face masks designed for chemical weapons attacks. "We have had some cases where, as we’ve monitored levels, it has risen high enough that we’ve directed use of gas masks," Davis said.
U.S. commanders in the region are monitoring the air quality constantly. "As they need to, commanders are directing forces to either stay indoors or don gas masks," Davis said. "We are continuing to take air samples and analyze what is going on and the concerns that may result from it."
ISIS set the fire Saturday, but Iraqi troops seized the flaming sulfur mine soon afterward.
The Iraqi government "is working to put out the fires, but it may take a couple days to do that, Davis said "… It’s a complicated fire to put out."
Andrew Tilghman is the executive editor for Military Times. He is a former Military Times Pentagon reporter and served as a Middle East correspondent for the Stars and Stripes. Before covering the military, he worked as a reporter for the Houston Chronicle in Texas, the Albany Times Union in New York and The Associated Press in Milwaukee.