Mattis Handshake Defense Secretary James N. Mattis congratulates Air Force Gen. Terrence J. O’Shaughnessy after he took command of North American Aerospace Defense Command and U.S. Northern Command during a ceremony at Peterson Air Force Base, Colo., May 24, 2018. Photo courtesy U.S. Northern Command SHARE: Download: Full Size (0.11 MB) Credit: Photo courtesy U.S. Northern Command VIRIN: 180524-F-ZZ999-046.JPG Photo Gallery