Army Gen. Martin E. Dempsey, right, chairman of the Joints Chiefs of Staff, speaks with Army Gen. Charles H. Jacoby Jr., left, commander of U.S. Northern Command and North American Aerospace Defense Command, and James H. Baker, the chairman’s strategist, during a strategic studies seminar at the Eisenhower Executive Office Building in Washington D.C., Dec. 2, 2014. DoD photo by U.S. Army Staff Sgt. Sean K. Harp

Army Spc. Cameron Huntington embraces his wife, Rebekah, shortly after he returned home from Afghanistan in the early morning hours on Fort Bragg, N.C., Nov. 28, 2014. Huntington is assigned to the 82nd Airborne Division's Combat Aviation Brigade. U.S. Army photo by Sgt. 1st Class Joseph Armas

Air Force Airman 1st Class Zach Wertz replaces old rope lights on an outdoor tree display on McConnell Air Force Base, Kan., Dec. 2, 2014. Wertz is an electrician assigned to the 22nd Civil Engineer Squadron. U.S. Air Force photo by Airman 1st Class Tara Fadenrecht

Marines finish a hike by calling cadence on Telegraph Pass in Yuma, Ariz., Nov. 26, 2014. The Marines are assigned to Marine Wing Support Squadron 371, based on Marine Corps Air Station Yuma, Ariz. U.S. Marine Corps photo by Cpl. Zachary Scanlon

U.S. sailors maneuver a drop tank across the flight deck of the of the aircraft carrier USS Carl Vinson in the Persian Gulf, Nov. 24, 2014. The Carl Vinson is conducting flight operations in the U.S. 5th Fleet area of responsibility supporting Operation Inherent Resolve. U.S. Navy photo by Petty Officer 2nd Class John Philip Wagner Jr.

U.S. sailors man a phone and distance line during an underway replenishment with the Military Sealift Command fast combat support ship USNS Rainier on the guided-missile destroyer USS Mitscher in the Arabian Gulf, Nov. 25, 2014. U.S. Navy photo by Petty Officer 2nd Class Anthony R. Martinez

Navy Petty Officer 3rd Class Maya Gengenbacher grinds a weld on a pipe on the aircraft carrier USS John C. Stennis in Bremerton, Wash., Nov. 25, 2014. U.S. Navy photo by Seaman Ignacio D. Perez

U.S. Navy Rear Adm. Brad Williamson waves to the Spanish navy frigate ESPS Reina Sofia from the bridge wing of the guided-missile cruiser USS Leyte Gulf in the Mediterranean Sea, Nov. 24, 2014. U.S. Navy photo by Petty Officer 2nd Class Amanda S. Kitchner