secretary. and general joseph dunford, the current chairman of the joint chiefs of staff. all three achieved the rare rank of four-star general. the first time there have ever been that be in the corps. dunford is making it clear he's not wordied about mattek taking the top civilian job. >> do i have any concerns? no. >> reporter: nobody can yet say how these four stars will deal with the controversial national security adviser, retired three-star army lieutenant general mike flynn, who was junior to them. these marines have personal bonds that are as deep as can be. on november 9, 2010, dunford broke the news to kelly his son, robert kelly, had been killed in afghanistan. a brotherhood of battle hardened senior marines, forged back in 2003, when mattis commanded the