Mock Door Training U.S. and NATO paratroopers conduct mock door exercises before participating in a Peacemaster Unity airborne operation at Aviano Air Base, Italy, Oct. 17, 2016. The U.S. paratroopers are assigned to the 173rd Airborne Brigade. Hundreds of paratroopers gathered at Aviano and simultaneously in Latvia, bringing together several partner and allied nations for one of the largest combined airborne operations. Army photo by Paolo Bovo SHARE: Download: Full Size (2.73 MB) Tags: Soldiers, Army, training Credit: Paolo Bovo VIRIN: 161017-A-JM436-151A.JPG Photo Gallery