A U.S. Air Force security forces Airman secures the outside of a hardened facility after neutralizing the opposing force during a combat training course on Ramstein Air Base, Germany, May 30, 2015. Battlefield Leaders Assaulter Course, Integrated Combat Essentials -- or BLAC ICE is designed to teach security forces members from multiple countries advanced tactics and shooting skills for use in the event of a base security breach. (U.S. Air Force photo/ Tech. Sgt. Ryan Crane)

U.S. and European security forces discuss their strategy prior to breaching a hardened facility during a combat training course on Ramstein Air Base, Germany, May 30, 2015. Battlefield Leaders Assaulter Course, Integrated Combat Essentials -- or BLAC ICE is designed to teach security forces members from multiple countries advanced tactics and shooting skills for use in the event of a base security breach. (U.S. Air Force photo/ Tech. Sgt. Ryan Crane)