U.S. Army Alpha Company, 3rd Battalion, 15th Infantry Regiment, scout snipers fire M110 sniper rifles Oct. 14, 2015, at Arta, Djibouti. ACO, assigned to Combined Joint Task Force-Horn of Africa, is the East Africa Response Force, the quick response force for all of the countries within the HOA. (U.S. Air Force photo by Senior Airman Peter Thompson/Released)