Army combat engineers attach a time fuse to a detonating-cord firing system so they can practice detonating a bomb remotely during training on Fort Bragg, N.C., Feb. 23, 2011. U.S. Army photo by Sgt. Michael J. MacLeod

U.S. Army Spc. Joshua Hutchins and Spc. Ryan Frye thread a Bangalore torpedo through a barrier of barbed wire during a combat engineer training class on Fort Bragg, N.C., Feb. 23, 2011. Hutchins and Frye are assigned to the 82nd Airborne Division’s 1st Brigade Combat Team.

U.S. Air Force Staff Sgt. Keo Khamonel waves to locals as he flies in the back a U.S. Air Force C-130 Hercules over Tumon Bay, Guam, Feb. 23, 2011. Khamonel is a U.S. Air Force C-130 Hercules loadmaster assigned to the 36th Airlift Squadron on Yokota Air Base, Japan. The U.S. and Japan are participating in Cope North, an annual exercise conducted between U.S. and Japanese forces U.S. Air Force photo by Staff Sgt. Angelita M. Lawrence

A U.S. Army Ranger candidate pulls himself along a suspended rope during the bridge and vertical haul line exercises that are part of mountaineer training on Camp Merrill, Dahlonega, Ga., Feb. 21, 2011. U.S. Army photo by John D. Helms

U.S. Navy Petty Officer 2nd Class Bryan Parker patrols down a street during a civil affairs assessment patrol in Now Zad, Afghanistan, Feb. 22, 2011. Parker, also known as "Doc," is assigned to the civil affairs team, 3rd Battalion, 2nd Marines. U.S. Marine Corps photo by 2nd Lt. Timothy Irish

U.S. Air Force Staff Sgt. Brett Hurley commands his military working dog, Rex, to jump over an obstacle course on Bagram Airfield, Afghanistan, Feb. 25, 2011. Hurley and Rex are assigned to the 455th Expeditionary Security Forces Squadron. U.S. Air Force photo by Senior Airman Sheila deVera

Defense Secretary Robert M. Gates, left, talks with Frank Buckles, the last living American World War I veteran, during a Pentagon ceremony March 6, 2008. Buckles died Feb. 27, 2011, at age 110. DOD file photo by R.D. Ward.

U.S. Navy sailors prepare a Remote Ordnance Neutralization System robot to approach a suspect vehicle during an Exercise Solid Curtain-Citadel Shield 2011 vehicle borne improvised explosive device drill in Jacksonville, Fla., Feb. 24, 2011. The weeklong series of anti-terrorism and force protection exercises involves Navy installations and activities. U.S. Navy photo by Petty Officer 2nd Gary Granger Jr.