Mattis Testimony Defense Secretary Jim Mattis testifies during a Senate Armed Services Committee hearing in Washington, D.C., Oct. 3, 2017. Mattis testified alongside Marine Corps Gen. Joe Dunford, chairman of the Joint Chiefs of Staff, about the political and security situation in Afghanistan. DoD photo by Army Sgt. James K. McCann SHARE: Download: Full Size (0.44 MB) Credit: Sgt. James K. McCann VIRIN: 171003-D-SW162-1221.JPG Photo Gallery