Spc. Leandro Gomez, a paratrooper assigned to 173rd Airborne Brigade, fires a M777A2 Howitzer during a live fire exercise at the 7th Army Joint Multinational Training Command's Grafenwoehr Training Area, Germany, April 30, 2015. (Markus Rauchenberger/U.S. Army)

Spc. Marquis Durham, right, and Spc. Robert Johnson, paratroopers assigned to the 173rd Airborne Brigade, prepare 155 mm rounds for firing with M777A2 Howitzers during a live fire exercise at the 7th Army Joint Multinational Training Command's Grafenwoehr Training Area, Germany, April 30, 2015. (Markus Rauchenberger/U.S. Army)

Troops with the 3rd Infantry Division prepare to dismount from their Bradley fighting vehicle to perform a security and reconnaissance mission during a situational training exercise in Hohenfels Training Area, Germany, on May 5, 2015. (Uriah Walker/U.S. Army)

The blast of an U.S. Army M1A2 Abrams Main Battle Tank firing the main gun sends up a cloud of flame and smoke during a live-fire exercise in Estonia on April 30, 2015. (Cody Harding/U.S. Army)

Former President George W. Bush leads current or former military service members on the W100K mountain bike ride across his ranch in Crawford, Texas, May 1, 2015. The 17 participants on this year?s ride were all wounded while serving in the global war on terror, and were invited to participate in this three-day event that covers 100 kilometers on and around the ranch. (Randall Stillinger/U.S. Army)

U.S. Army soldiers from Team Eagle, Task Force 2-7 Infantry pull into the General Silvestras Zlikaliskas Training Area in Pabrade, Lithuania, May 1, 2015, in anticipation of a live-fire exercise. (James Avery/U.S. Army)

Sgt. Brandon Painter of the South Carolina Army National Guard, uses a M240 to assist with establishing a perimeter defense around a U.S. Army UH-60 Black Hawk helicopter while Warrant Officer Joshua O?Handley calls for a MEDEVAC as part of a personnel recovery and downed aircraft training exercise at the McCrady Training Center, Eastover, S.C., May 3, 2015. (Brian Calhoun/U.S. Army)

U.S. soldiers assigned to 2nd Battalion, 5th Cavalry Regiment, 1st Brigade Combat Team, 1st Cavalry Division, maneuver M1A2 Abrams tanks to the Rose Barracks railhead station May 5, 2014, in Vilseck, Germany. (Gertrud Zach/U.S. Army)

U.S. soldiers, from the 982nd Combat Camera Company (Airborne) and 55th Signal Company (Combat Camera), participate in Operation Skyfall- Espa?a, in Madrid, Spain, May 5, 2015. (Jesus F. Guerrero/U.S. Army)