A U.S. Air Force F-16 Fighting Falcon pilot assigned to the 55th Expeditionary Fighter Squadron waits on the flight line during a hot pit refueling operation as part of an Agile Combat Employment exercise at an undisclosed location, Dec. 21, 2021. ACE is an operational concept that leverages networks of well-established and austere air bases, multi-capable Airmen, pre-positional equipment, and airlift to rapidly deploy, disperse and maneuver combat capability throughout a theater. Paired with aircraft refueling, arming and limited maintenance activities, ACE expands the number of bases from which air forces can generate combat sorties. (US Air Force photo by Staff Sgt. Joseph Pick)