President Barack Obama and Gen. Martin Dempsey, Chairman of the Joint Chiefs of Staff, attend the September 11th Observance Ceremony at the Pentagon Memorial in Arlington, Va., Sept. 11, 2014.

President Barack Obama and Gen. Martin Dempsey, Chairman of the Joint Chiefs of Staff, attend the September 11th Observance Ceremony at the Pentagon Memorial in Arlington, Va., Sept. 11, 2014.

President Barack Obama, Defense Secretary Chuck Hagel, and Gen. Martin Dempsey, Chairman of the Joint Chiefs of Staff, listen to the national anthem during the September 11th Observance Ceremony at the Pentagon Memorial in Arlington, Va., Sept. 11, 2014.

President Barack Obama, Defense Secretary Chuck Hagel, and Gen. Martin Dempsey, Chairman of the Joint Chiefs of Staff, listen to the national anthem during the September 11th Observance Ceremony at the Pentagon Memorial in Arlington, Va., Sept. 11, 2014.

President Barack Obama, Defense Secretary Chuck Hagel and General Martin Dempsey, Chairman of the Joint Chiefs of Staff, bow their heads as Chaplain Col. Michael Brainerd delivers the invocation during a Memorial Day ceremony at the Arlington National Cemetery Memorial Amphitheater in Arlington, Va., May 26, 2014.

President Barack Obama, Defense Secretary Chuck Hagel and General Martin Dempsey, Chairman of the Joint Chiefs of Staff, bow their heads as Chaplain Col. Michael Brainerd delivers the invocation during a Memorial Day ceremony at the Arlington National Cemetery Memorial Amphitheater in Arlington, Va., May 26, 2014.

President Barack Obama, with Maj. Gen. Jeffrey S. Buchanan, Commanding General, U.S. Army Military District of Washington, participates in a Memorial Day wreath laying at the Tomb of the Unknown Soldier at Arlington National Cemetery in Arlington, Va., May 26, 2014.

President Barack Obama, with Maj. Gen. Jeffrey S. Buchanan, Commanding General, U.S. Army Military District of Washington, participates in a Memorial Day wreath laying at the Tomb of the Unknown Soldier at Arlington National Cemetery in Arlington, Va., May 26, 2014.

President Barack Obama, First Lady Michelle Obama, Oprah Winfrey, and Stedman Graham applaud a performance by Arturo Sandoval during a dinner honoring the 2013 Presidential Medal of Freedom awardees at the Smithsonian National Museum of American History in Washington, D.C., Nov. 20, 2013.

President Barack Obama, First Lady Michelle Obama, Oprah Winfrey, and Stedman Graham applaud a performance by Arturo Sandoval during a dinner honoring the 2013 Presidential Medal of Freedom awardees at the Smithsonian National Museum of American History in Washington, D.C., Nov. 20, 2013.

Nov. 20, 2013 "The President and First Lady, and former President Bill Clinton and Hillary Clinton, join others during a wreath laying ceremony at the gravesite of President John F. Kennedy at Arlington National Cemetery to mark the 50th anniversary of Kennedy’s assassination." (Official White House Photo by Pete Souza) This official White House photograph is being made available only for publication by news organizations and/or for personal use printing by the subject(s) of the photograph. The photograph may not be manipulated in any way and may not be used in commercial or political materials, advertisements, emails, products, promotions that in any way suggests approval or endorsement of the President, the First Family, or the White House.

Nov. 20, 2013
"The President and First Lady, and former President Bill Clinton and Hillary Clinton, join others during a wreath laying ceremony at the gravesite of President John F. Kennedy at Arlington National Cemetery to mark the 50th anniversary of Kennedy's assassination." 
(Official White House Photo by Pete Souza)

This official White House photograph is being made available only for publication by news organizations and/or for personal use printing by the subject(s) of the photograph. The photograph may not be manipulated in any way and may not be used in commercial or political materials, advertisements, emails, products, promotions that in any way suggests approval or endorsement of the President, the First Family, or the White House.

President Barack Obama, with Major General Jeffery S. Buchanan, Commanding General U.S. Army Military District of Washington, places a wreath at the Tomb of the Unknowns on Veterans Day at Arlington National Cemetery in Arlington, Va., Nov. 11, 2013.

President Barack Obama, with Major General Jeffery S. Buchanan, Commanding General U.S. Army Military District of Washington, places a wreath at the Tomb of the Unknowns on Veterans Day at Arlington National Cemetery in Arlington, Va., Nov. 11, 2013.

President Barack Obama greets children at the September 11th Observance Ceremony at the Pentagon Memorial in Arlington, Va., Sept. 11, 2013.

President Barack Obama greets children at the September 11th Observance Ceremony at the Pentagon Memorial in Arlington, Va., Sept. 11, 2013.

President Barack Obama talks with General Martin Dempsey, Chairman of the Joint Chiefs of Staff, after attending the Armed Forces farewell tribute for Defense Secretary Leon Panetta at Joint Base Myer-Henderson in Arlington, Va., Feb. 8, 2013.

President Barack Obama talks with General Martin Dempsey, Chairman of the Joint Chiefs of Staff, after attending the Armed Forces farewell tribute for Defense Secretary Leon Panetta at Joint Base Myer-Henderson in Arlington, Va., Feb. 8, 2013.

President Barack Obama prepares to place a wreath at the Tomb of the Unknowns at Arlington National Cemetery in Arlington, Va., Nov. 11, 2012.

President Barack Obama prepares to place a wreath at the Tomb of the Unknowns at Arlington National Cemetery in Arlington, Va.,  Nov. 11, 2012.