The U.S. military will expand operations at Iraq's al Asad air base as part of its preparations for the invasion of Mosul, where thousands of Islamic State militants have established the group's largest stronghold outside of Syria.



Defense Secretary Ash Carter announced Wednesday plans to deploy an additional 615 American troops to Iraq over the next several weeks. They will help support the Iraqi-led invasion planned for this fall.



Al Asad, a massive airfield in Anbar province, was a major hub for U.S. Marines throughout the Iraq war. Soon, it will see the arrival of more personnel and the installation of new technology that can support night operations, a Defense Department official said. The U.S. will set up a new "instrument landing system," which will cover the airfield with radio signals that help pilots to land safely in conditions when they cannot see the runway, such as at night or in bad weather, the official said.



The equipment can be deployed on short notice.





"A lot of those [615] folks will be going to al Assad air base," said Navy Capt. Jeff Davis, a Pentagon spokesman, who described the facility as "lacking in a lot of the basic capabilities that it needs to be able to conduct this high throughput of operations as the Mosul operation progresses."

The additional American personnel there will be focused primarily on logistics and maintenance, Davis said.

"They will be helping with airfield operations and bringing the state of those airfields up to a level to be able to support a greater pace of operations," he added.

The added manpower and aviation upgrades at al Asad underscore concerns about Iraqi security that extend beyond Mosul, which has been a primary objective for U.S. and Iraqi forces.

"There’s two things really going on — one obviously is the retaking of Mosul. But two is helping to ensure the Iraqis’ lasting victory in these places they have already liberated," Davis said. "And even though Mosul is a very large city that [the Islamic State group] holds, there still is a very large swath of territory and that is going to require our assistance as well, in all likelihood."

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Al Asad, not far from the Syrian border. It's centrally located near much of the Islamic State group’s territory and could be a strategic location for future operations targeting Raqqa, ISIS's self-proclaimed capital.

After the 2003 U.S. invasion of Iraq, al Asad became one of the largest American air bases there. It was known among Marines as "Camp Cupcake" because of its amenities that included fitness centers and high-quality dining facilities.

Since the return of U.S. forces to Iraq in 2014, al Asad has been the site of American-led training efforts for the Iraqi security forces. There, the U.S. military also maintains an M142 High Mobility Artillery Rocket System

, or HIMARS, which can deliver long-range precision strikes.