U.S. troops in Iraq are setting up a train-advise-and-assist team at a forward operating base near the Islamic State group’s front lines outside Mosul, not far from the site of a recent chemical weapons attack.

The Nineveh Operations Center in the farming village of Makhmour will be a primary base for the U.S. to support the Iraqis’ long-awaited battle to seize Mosul from Islamic State militants, also known as ISIS or ISIL, a U.S. military official said.

A large convoy of Iraqi army forces began arriving at the base in Makhmour in early February. Iraq’s defense ministry plans to deploy some 4,500 soldiers to the area for the Mosul operation, Iraqi officials said.

“There’s a lot going on in Makhmour. That’s where one of our operations centers is located. So there are American advise-and-assist capabilities there,” said Army Col. Steve Warren, a U.S. Defense Department spokesman in Baghdad.