

US soldiers observe the area as they expect a Taliban attack near the town of Walli Was in Paktika province, near the border with Pakistan, November 3, 2012. Goran Tomasevic/Reuters
A self portrait of the US navy aviator Lt. j.g. Douglas Spence, 27, of Houston, Texas, on board an F/A18F Super Hornet with the VFA-102, "Diamondbacks," during a training mission in Japan, Dec. 20, 2012. The squadron is assigned to the USS George Washington aircraft carrier. The United States has more than 50,000 troops in Japan and in a region anxious over the rise of China's military might, squadrons like the Diamondbacks are an important component of the U.S. military presence in the Pacific. Douglas Spence/U.S. Navy/AP
A first-year midshipman, or plebe, is splashed with mud while participating in Sea Trials at the US Naval Academy in Annapolis, Maryland, May 15, 2012. Sea Trials, modeled after the Marine Corps' Crucible and the Navy's Battle Stations recruit programs, is an annual capstone event for fourth class midshipmen and serves as a leadership challenge for upper class midshipmen, who lead each activity during the exercise. Chad Runge/U.S. Navy/Reuters
An F-15E Strike Eagle receives fuel from a 100th Air Refueling Wing KC-135 Stratotanker during an aerial refuelling mission over the Atlantic Ocean, September 10, 2012. The refuelling was part of a training mission for the 48th Fighter Wing, RAF Lakenheath and 100th ARW. Ethan Morgan/U.S. Air Force/Reuters
A US Army soldier with the 10th Special Forces Group and his military working dog jump off the ramp of a CH-47 Chinook helicopter from the 160th Special Operations Aviation Regiment during water training over the Gulf of Mexico, March 1, 2011. A military canine accompanied Navy SEAL Team 6 commandos in the raid that killed Al Qaeda leader Osama bin Laden, The New York Times and other US media reported. Manuel J. Martinez/U.S. Air Force/Reuters
US President Barack Obama (l.) and US Army General Michael S. Linnington (2nd l.), Commanding General of the Military District of Washington, stand during a wreath-laying ceremony for Veterans Day at Arlington National Cemetery in Arlington, Virginia, November 11, 2012. Jonathan Ernst/Reuters
Capt. Sara Rodriguez of the 101st Airborne Division pours water on her face during the expert field medical badge testing at Fort Campbell, Ky., May 9, 2012. Female soldiers are moving into new jobs in once all-male units as the U.S. Army breaks down formal barriers in recognition of what's already happened in wars in Iraq and Afghanistan. Kristin M. Hall/AP
US Army soldiers clear debris from the Breezy Point neighborhood which was left devastated by Hurricane Sandy in the New York borough of Queens November 12, 2012. Adrees Latif/Reuters
A US soldier stands next to a Patriot surface-to-air missile battery at an army base in Morag May 26, 2010. Peter Andrews/Reuters
The US Navy's USS Enterprise aircraft carrier transits the Suez Canal on its way from the Mediterranean to the Gulf near Ismalia, in this August 1, 2007 file photo. The United States is moving warships and aircraft, including the USS Enterprise, into the Mediterranean Sea near Libya, according to US officials. Reuters
A US Airborne soldier exchanges a fist-bump with a Haitian youth in downtown Port-au-Prince, Haiti, in this United Nations Stabilization Mission in Haiti (MINUSTAH), January 26, 2010. Marco Dormino/UN/MINUSTAH/Reuters
United States Coast Guard member Ryan Hoyt works on the rig of the Coast Guard Cutter Barque Eagle as it sits in the harbour of New York August 5, 2011. The USCGC Eagele was originally operated by Nazi Germany to train cadets for the German Navy. The ship was taken by the US as a war prize after World War II. In 1946, a U.S. Coast Guard crew aided by a German crew, sailed the ship to its new homeport in New London, Connecticut. Shannon Stapleton/Reuters
Josh Mayeux, network defender, works at the Air Force Space Command Network Operations & Security Center at Peterson Air Force Base in Colorado Springs, Colorado July 20, 2010. US national security planners are proposing that the 21st century's critical infrastructure -- power grids, communications, water utilities, financial networks -- be similarly shielded from cyber marauders and other foes. The ramparts would be virtual, their perimeters policed by the Pentagon and backed by digital weapons capable of circling the globe in milliseconds to knock out targets. Rick Wilking/Reuters
Graduates swear in after U.S. President Barack Obama gives the 2010 commencement address at Mitchie Stadium at the U.S. Military Academy at West Point in New York, May 22, 2010. Larry Downing/Reuters
Cpl. Nicholas Brazil, a crew chief in the US Marine Corps, fires a machine gun from a Huey attack helicopter during live-fire training. This was part of a multinational military exercise at Pohakuloa Training Area in Hawaii on July 22, 2012. Hugh Gentry/Reuters