Pentagon Departure Defense Secretary Ash Carter walks down a hallway as he leaves the Pentagon on his last day in office, Jan. 19, 2017. DOD photo by Air Force Tech. Sgt. Brigitte N. Brantley SHARE: Download: Full Size (1.22 MB) Credit: Brigitte N. Brantley VIRIN: 170119-D-GO396-0514.JPG Photo Gallery