An Improvised Explosive Device killed an American soldier in northern Iraq on Thursday, marking the first known U.S. combat death in the battle to eject ISIS from Mosul.

The Pentagon identified the casualty on Friday afternoon as Chief Petty Officer Jason C. Finan, 34, from Explosive Ordnance Disposal Mobile Unit Three, based at Naval Amphibious Base Coronado.

“Finan joined the Navy in 2003. He had been awarded Master Explosive Ordnance Disposal, Naval Parachutist and Diver insignia and had received many decorations, including the Navy and Marine Corps Commendation Medal with Combat V device and the Joint Meritorious Unit Award,” reported Military.com, quoting a statement from the Navy.

“The entire Navy Expeditionary Combat Command family offers our deepest condolences and sympathies to the family and loved ones of the Sailor we lost,” said Navy Expeditionary Combat Command commander Rear Admiral Brian Brakke.

Foreign Policy notes it was the second combat death suffered by American forces fighting ISIS this month, and the fourth since U.S. troops were deployed in Iraq last year. Also, a U.S. service member was killed in Afghanistan on Wednesday when an Afghan soldier turned coat and opened fire.

Thursday’s incident occurred northeast of Mosul, in an area where U.S. advisers are embedded with Kurdish and Iraqi troops. The Pentagon has said there are “over one hundred” such advisers on the ground near Mosul, helping to direct U.S. artillery and airstrikes.

New York Daily News reports Chief Petty Officer Finan was traveling in an armored vehicle near the town of Bashiqa, north of Mosul, with Iraqi special forces when it was hit by a roadside bomb. He died after he was evacuated to Irbil for medical treatment.

According to ABC News, the American “had been operating as an explosive ordnance disposal specialist in support of the Iraqi Kurdish force known as the peshmerga.” Five Iraqi soldiers were also said to be wounded in the attack.

ABC’s report notes that, in addition to roadside bombs and other booby traps, ISIS forces have been defending Mosul with “armored trucks packed with explosives and driven by suicide bombers.” Iraqi forces have reportedly grown more adept at destroying car bombs with their tank guns under American tutelage.

Defense Secretary Ash Carter described Finan’s death as a “reminder that our people who are participating in the counter-ISIL campaign, whether they be flying aircraft or working with the Iraqi security forces and the other forces and enabling their consistent advances of the kind that we see in the region of Mosul today, are in harm’s way.”

“This is necessary work, because it’s necessary for us to destroy ISIL in Iraq and Syria,” said Carter. “Therefore, it’s necessary for us to enable in this case the Iraqi security forces and the peshmerga in northern Iraq, and it appears that it was in that role that the service member was killed.”

The BBC quotes U.S. Lt. Gen. Stephen Townsend warning that ISIS is a “brutal opponent,” which is “adaptable, creative, and cunning.”

“They’re using human shields in there,” Townsend said of Islamic State forces in Mosul and its surrounding towns. “They saw people’s heads off on TV, they drown people and video it, they burn people alive in cages, they crucify people and they drive over people on the street with bulldozers.”