A 321st Special Tactics Squadron combat controller hammers into place a distance marker before the start of an austere landing exercise at Plovdiv, Bulgaria, Feb. 9, 2016. Combat controllers supported the training for multiple aircraft deployed to Bulgaria as part of Operation Atlantic Resolve which aims to assure the U.S.’s commitment to the security and stability of Europe. (U.S. Air Force photo by Airman 1st Class Luke Kitterman/Released)