U.S. Army soldiers with the 173rd Cavalry Airborne Reconnaissance Squadron, Fort Bragg, N.C., set up a perimeter during a Mobility Air Forces Exercise at the Nevada Test and Training Range in the desert of southern Nevada on Nov. 18, 2009. The soldiers are taking part in the bi-annual U.S. Air Force Weapons School exercise, which provides realistic training for combat Air Force, mobility Air Force and U.S. Army personnel. Approximately 40 C-17 and C-130 aircraft from Air Force bases around the world dropped approximately 400 soldiers on the training range. The exercise also allows soldiers the opportunity to use range facilities to conduct urban ground operations training.