Vice President Joe Biden, left, President Barack Obama, second from left, Deborah Mullen and her husband, Navy Adm. Mike Mullen, outgoing chairman of the Joint Chiefs of Staff, observe the honor guard pass and review at the Chairman of the Joint Chiefs of Staff change of responsibility ceremony on Joint Base Myer-Henderson Hall, Va., Sept. 30, 2011. Mullen retired during the ceremony, bringing to a close his 43-year military career. DOD photo by U.S. Navy Petty Officer 1st Class Chad J. McNeeley

Navy Adm. Mike Mullen, 17th chairman of the Joint Chiefs of Staff, and his wife, Deborah, are piped ashore at the Chairman of the Joint Chiefs of Staff change of responsibility ceremony on Joint Base Myer-Henderson Hall, Va., Sept. 30, 2011. During the ceremony, Mullen retired after 43 years of military service and Army Gen. Martin E. Dempsey accepted the role of chairman. DOD photo by U.S. Navy Petty Officer 1st Class Chad J. McNeeley

Defense Secretary Leon E. Panetta, right, and Canadian Defence Minister Peter MacKay, left, hold a joint media availability event outside the Pentagon, Sept. 30, 2011. The two defense leaders met earlier to discuss a broad range of bilateral security issues. DOD photo by R. D. Ward

Defense Secretary Leon E. Panetta escorts Canadian Minister of Defense Peter MacKay through an honor cordon at the Pentagon, September 30, 2011. The two leaders met to discuss a range of defense issues. DOD photo by Erin A. Kirk-Cuomo

Navy Adm. Mike Mullen, left, outgoing chairman of the Joint Chiefs of Staff, congratulates the new chairman of the Joint Chiefs of Staff, Army Gen. Martin E. Dempsey, during the Chairman of the Joint Chiefs of Staff change of responsibility ceremony on Joint Base Myer-Henderson Hall, Va., Sept. 30, 2011. Mullen retired after 43 years of service and Dempsey became the 18th chairman of the Joint Chiefs of Staff during the ceremony. DOD photo by U.S. Air Force Tech. Sgt. Jacob N. Bailey

Army Gen. Martin E. Dempsey delivers remarks during the chairman of the Joint Chiefs of Staff change of responsibility ceremony at Summerall Field, Joint Base Myer-Henderson Hall, Va., Sept. 30, 2011. Dempsey, the18th chairman of the Joint Chiefs of Staff, succeeded Navy Adm. Mike Mullen, outgoing chairman, during the ceremony. DOD photo by U.S. Air Force Tech. Sgt. Jacob N. Bailey

President Barack Obama, left, shares a moment with Navy Adm. Mike Mullen, outgoing chairman of the Joint Chiefs of Staff, during the Chairman of the Joint Chiefs of Staff change of responsibility ceremony on Joint Base Myer-Henderson Hall, Va., Sept. 30, 2011. Mullen was succeeded by Army Gen. Martin E. Dempsey, who became the18th chairman of the Joint Chiefs of Staff, during the ceremony. DOD photo by U.S. Air Force Tech. Sgt. Jacob N. Bailey

President Barack Obama greets Navy Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, and Defense Secretary Leon E. Panetta at the Joint Chiefs of Staff change of responsibility ceremony on Joint Base Myer-Henderson Hall, Va., Sept. 30, 2011. During the ceremony, Mullen retired after 43 years of service, transferring the chairman's responsibilty's to Army Gen. Martin Dempsey. DOD photo by U.S. Navy Petty Officer 1st Class Chad J. McNeeley