U.S. Air Force 2nd Lt. Matthew Keelin, left, a doctor assigned to the Chemical, Biological, Radiological, Nuclear and high-yield Explosives Enhanced Response Force Package, Oregon Air National Guard, examines a patient with a leg injury near Joint Base Elmendorf-Richardson in Alaska March 27, 2014, during Ardent Sentry 2014. Ardent Sentry is a NORAD and U.S. Northern Command (USNORTHCOM)-directed exercise focusing on defense support of civil authorities in response to simulated weather, security and disaster contingencies. While Ardent Sentry is primarily a command post exercise, several field training events were conducted at various locations within the USNORTHCOM area of responsibility.