Direct proof of use
U.S. Apache helicopters entered the Iraq fight against the Islamic State by June 2016. A Combined Joint Task Force - Operation Inherent Resolve news release, citing Defense Secretary Ash Carter and a Defense Department spokesman, said an Apache strike destroyed an ISIL vehicle-borne improvised explosive device near Qayyarah, Iraq, on June 12, 2016 in support of Iraqi security forces operating in the Tigris River Valley.
Official U.S. imagery and reporting then documented AH-64E Apaches with Task Force Saber at Erbil, Iraq. A January 10, 2017 CENTCOM image caption identified Bravo Troop, 4th Squadron, 6th Cavalry Regiment crews conducting pre-flight on an AH-64E Apache at Camp Erbil and said U.S. Army aviation was enabling partner forces to defeat ISIL by providing battlefield air support.
Sources: CJTF-OIR Apache Counter-ISIL Fight, CENTCOM Task Force Saber Air Mission
Task Force Saber operations
Task Force Saber brought the AH-64E into the Operation Inherent Resolve aviation package in 2017. CENTCOM's July 24, 2017 article on the 29th Combat Aviation Brigade's 4th Squadron, 6th Cavalry Regiment described the unit as providing reconnaissance, surveillance, logistical support, and offensive strike capabilities while supporting partner forces in Iraq and Syria.
The same article identified the AH-64E Apache as one of Task Force Saber's fires platforms, paired with RQ-7Bv2 Shadow unmanned aircraft for target identification and handoff. It also stated that the 4th Squadron, 6th Cavalry Regiment brought the first AH-64E helicopters to Operation Inherent Resolve and that its crews were used against enemy targets.
Sources: CENTCOM Task Force Saber Article
Continuity in late 2017
The Apache role continued after the 4th Squadron, 6th Cavalry Regiment handed Task Force Saber to the 2nd Squadron, 17th Cavalry Regiment on August 29, 2017. DVIDS reporting said 2-17th Cavalry became the primary attack and reconnaissance squadron for CJTF-OIR at Erbil and would provide attack helicopter and tactical unmanned aerial-system capability to coalition ground forces.
A linked September 2, 2017 DVIDS image at Qayyarah West Airfield identified C Troop, 2nd Squadron, 17th Cavalry Regiment personnel maintaining an AH-64E Apache and said the unit would provide attack, reconnaissance, and surveillance capability for CJTF-OIR while commanding Task Force Saber.
Sources: DVIDS 2-17 Cav Takes Reins, DVIDS 2-17 Cav AH-64E Maintenance