Mattis Arrival Defense Secretary James N. Mattis is greeted by Air Force Gen. Lori Robinson, commander of U.S. Northern Command and North American Aerospace Defense Command, as he arrives at Peterson Air Force Base, Colo., May 22, 2018. Air Force photo by Senior Airman Dennis Hoffman SHARE IMAGE: Download Image: Full Size (0.08 MB) Photo By: Senior Airman Dennis Hoffman VIRIN: 180523-D-XT155-006.JPG Photo Gallery