U.S. Air Force General Terrence J. O'Shaughnessy, commander of the North American Aerospace Defense Command and U.S. Northern Command, and Department of Homeland Security Secretary Kirstjen Nielsen answer questions from the media during a press availability inside command's operations center on Peterson Air Force Base, Sept. 6, 2018. During the press event the two discussed the command's homeland defense role from a multi-domain perspective, including the space, missile, air, maritime and cyber domains. (U.S. Air Force photo by Tech. Sgt. Joe Laws)