Nellis Air Force Base is known by the USAF as the "Home of the Fighter Pilot" and is the Air Force's focus for advanced combat training. The main unit at Nellis is the USAF Warfare Center, which coordinates training for composite strike forces involving aircraft types from across the USAF inventory, accompanied by air and ground units of the US Army, US Navy, US Marines, and aircraft from other NATO and allied nations. Training is delivered through a series of exercises which typically take place at the Nevada Test and Training Range (NTTR), the primary examples being Exercise Red Flag and Exercise Green Flag (West).