President Barack Obama participates in the wreath-laying ceremony at the Tomb of the Unknowns at Arlington National Cemetery on Memorial Day, May 27, 2013, in Arlington, Va. (AP Photo/Pablo Martinez Monsivais)

Photo by: Pablo Martinez Monsivais

President Barack Obama participates in the wreath-laying ceremony at the Tomb of the Unknowns at Arlington National Cemetery on Memorial Day, May 27, 2013, in Arlington, Va. (AP Photo/Pablo Martinez Monsivais)