When terrorists attacked the United States on 11 September 2001, Air Force Reservists responded in full measure. Air Force Reserve F-16 Fighting Falcon fighters flew Combat air patrols (CAPs) protecting America's cities while AFRC KC-135 Stratotankers and E-3 Sentry AWACs aircraft supported with air refuelings and security. In October 2001, the United States initiated the Global War on Terrorism as military forces entered Afghanistan to combat the Taliban in Operation Enduring Freedom (OEF). Air Force Reserve special operations MC-130 Combat Talon aircraft became the first fixed-wing aircraft to penetrate Afghan airspace while Air Force Reserve F-16 crews, already deployed in theater for Operation Southern Watch, performed the first combat missions.