General Terrence J. O'Shaughnessy, commander of North American Aerospace Defense Command and U.S. Northern Command, talks with Department of Homeland Security Secretary Kirstjen Nielsen just prior to entering the NORAD and USNORTHCOM headquarters on September 6, 2018. O'Shaughnessy and Nielsen met to discuss the strong relationship between the agency and the commands, and to discuss the complementary roles of homeland security and the commands' top priority, homeland defense. (Photo by Jeff Fitzmorris)