A crew chief assigned to the 175th Aircraft Maintenance Squadron, Maryland Air National Guard, services an A-10C Thunderbolt II aircraft with liquid oxygen during Saber Strike 15, Ämari Air Base, Estonia, June 8, 2015. Saber Strike is an exercise that aims to continue to improve U.S. interoperability with ally and partner nations, while increasing their capacity to conduct a full spectrum of military operations. (Air National Guard photo by Tech. Sgt. Christopher Schepers)