Image 0 of 9Soldiers practice loading into a UH-60 Black Hawk helicopter on July 21, 2017, at Bezmer Air Base, Bulgaria, during Saber Guardian 17. (Spc. Thomas Scaggs/Army) U.S. Marine veteran Lance Cpl. Jeff DeYoung carries Cena, a 10-year-old black lab who was a military service dog, aboard the LST 393, where Cena was put down on July 26, 2017, in Muskegon, Mich. Cena was diagnosed with an aggressive form of bone cancer after DeYoung noticed he wasn't putting weight on his front left leg. (Joel Bissell /Muskegon Chronicle via AP) Joint terminal attack controllers wave at an A-10 Thunderbolt II attack aircraft on July 19, 2017, during a show of force on the Nevada Test and Training Range. (Senior Airman Kevin Tanenbaum/Air Force) Navy Chief Petty Officer Joseph Tsicouris loads an Evolved Sea Sparrow missile into a NATO Sea Sparrow launcher on July 20, 2017, on the missile deck of the USS America in the Pacific Ocean during the ship's maiden deployment. (Petty Offier 2nd Class Alexander A. Ventura II/Navy) Special operations forces from the U.S., Hungary, Romania, Slovenia, and Croatia assault a building from U.S. Army UH-60 helicopters on July 12, 2017, while Hungarian SOF fast rope from a Hungarian Mi-8 (Hip) Multirole Medium-Lift Helicopter during exercise Black Swan in Szolnok, Hungary. (Staff Sgt. Aaron Duncan/Special Operations Command) U.S., Italian and Romanian soldiers seize an airfield on July 24, 2017, during Saber Guardian 17 at Turzii, Romania. (Sgt. Timothy Pike/Army) Marines fire an 81 mm mortar on July 21, 2017, during Exercise Talisman Saber 17 with Australian forces at Shoalwater Bay Training Area, Australia. (Lance Cpl. Stormy Mendez/Marine Corps) Air Force load crew members work together on July 21, 2017, during a quarterly load competition at Hill Air Force Base, Utah. (R. Nial Bradshaw/Air Force) Sailors heave lines to load a landing craft personnel light onto the boat deck of the amphibious dock landing ship USS Ashland (LSD 48) on July 25, 2017, after the completion of Talisman Saber 2017. (MC3 Jonathan Clay/Navy)