Wreaths were placed on headstones by volunteers during the Wreaths Across America event in Arlington National Cemetery, Dec. 12, 2015, in Arlington, Va. (Rachel Larue/U.S. Army)

Capt. Joshua Gorczynski, commander of Troop A,1st Squadron, 3d Cavalry Regiment, gives a mission brief Dec. 12, 2015, in the Fort Hood training area, part of a two-week long field exercise for the 3rd Cavalry Regiment to prepare for an upcoming rotation to the National Training Center in Fort Irwin, Calif. (Erik Warren/U.S. Army)

Sgt. Glenn Prause and Sgt. Andrew Elias conduct inventories of a Forward Repair System with Clinton Kerney, a contractor from Kellogg, Brown and Root at Mumaiciai, Lithuania, Dec. 13, 2015, part of establishing a forward storage site by U.S. Army Europe and Army Materiel Command. (Randy Ready/U.S. Army)

Meadows Elementary School students look out the window of an M109 Paladin Dec. 14, 2015, at Fort Hood, Texas. After handing out more than 200 holiday stockings to Fort Hood troops during a visit with their Adopt-A-School program partner unit, students explored different types of military vehicles to get a glimpse of what soldiers do on a regular basis. (Brandon Banzhaf/U.S. Army)

Baylor University athletic coaches lead Fort Hood soldiers through a combination of stretches and workouts Dec. 11, 2015, during a two-day physical training seminar with commanders and physical trainers from 91st Engineer Battalion, 1st Armored Brigade Combat Team, 1st Cavalry Division. (Fred Brown/U.S. Army)

Paratroops from the 82nd Airborne Division exit a CH-47 Chinook from the 82nd Combat Aviation Brigade over Sicily Drop Zone during an airborne jump at Fort Bragg, N.C., Dec. 15, 2015. (Christopher Freeman/U.S. Army)

U.S. paratroops assigned to the 2nd Battalion, 503rd Infantry Regiment, 173rd Airborne Brigade, participate in the battalion run at Caserma Del Din, Vicenza, Italy, Dec. 16, 2015. (Paolo Bovo/U.S. Army)

A soldier assigned to the 15th Engineer Battalion, 18th Military Police Brigade, moves tactically during a live-fire convoy exercise at the 7th Army Joint Multinational Training Command?s Grafenwoehr Training Area, Grafenwoehr, Germany, Dec. 15, 2015. (Emily Houdershieldt/U.S. Army)