Defense Secretary Ash Carter prepares to depart Joint Base Andrews, Md., Aug. 15, 2015, to attend a memorial ceremony in Chattanooga, Tenn., to honor the sailor and four Marines killed July 16, 2015. DoD photo by U.S. Air Force Master Sgt. Adrian Cadiz

A memorial stands outside the Armed Forces Recruiting Center in Chattanooga, Tenn., Aug. 13, 2015, to honor the four Marines and sailor killed during the July 16 shooting in the Navy Operational Support Center Chattanooga. Defense leaders and Tennessee officials joined Vice President Joe Biden in an Aug. 15 ceremony to honor the five fallen service members. U.S. Navy photo by Petty Officer 2nd Class Justin Wolpert

Army Gen. Martin E. Dempsey, chairman of the Joint Chiefs of Staff, takes questions from airmen during a town hall meeting at Creech Air Force Base, Nev., Aug. 12, 2015. The base is a command and control facility used to engage in daily overseas contingency operations of remotely piloted aircraft systems, which fly missions across the globe. DoD photo by D. Myles Cullen

Left to right: outgoing Army Chief of Staff Gen. Ray Odierno; Defense Secretary Ash Carter; Army Secretary John M. McHugh; Army Gen. Martin E. Dempsey, chairman of the Joint Chiefs of Staff; and incoming Army Chief of Staff Gen. Mark A. Milley stand at attention during the change-of-responsibility ceremony on Joint Base Myer-Henderson Hall in Arlington, Va., Aug. 14, 2015. During the ceremony, outgoing Odierno relinquished duties to Milley. DoD photo by U.S. Army Sgt First Class Clydell Kinchen

Left to right: Defense Secretary Ash Carter; Army Secretary John M. McHugh; Army Gen. Martin E. Dempsey, chairman of the Joint Chiefs of Staff; and incoming Army Chief of Staff Gen. Mark A. Milley render honors during a change-of-responsibility ceremony on Joint Base Myer-Henderson Hall in Arlington, Va., Aug. 14, 2015. During the ceremony, outgoing Army Chief of Staff Gen. Ray Odierno relinquished duties to Milley. DoD photo by U.S. Army Sgt. 1st Class Clydell Kinchen

U.S. Army Sgt. Maj. Jody Volz, adviser for Train, Advise and Assist Command South in Afghanistan, flies over Kandahar, Afghanistan, Aug. 4, 2015, with Afghan army and command leaders to gain situational awareness and a shared understanding of key terrain in southern Afghanistan. U.S. Navy photo by Lt. Kristine Volk

Soldiers help extinguish a small fire while battling the Rocky Fire near Clear Lake, Calif., Aug. 12, 2015. The soldiers are California National Guardsmen assigned to the 578th Brigade Engineer Battalion, and the 1st Battalion, 18th Cavalry, 79th Infantry Brigade Combat Team. California Army National Guard photo

U.S. Marines distribute water to civilians as part of Typhoon Soudelor relief efforts in Saipan, Aug. 12, 2015. The Marines are assigned to Combat Logistics Battalion 31, 31st Marine Expeditionary Unit, which is assisting local and federal agencies after the typhoon devastated the island Aug. 2-3. U.S. Marine Corps photo by Lance Cpl. Brian Bekkala