GRAND FORKS AIR FORCE BASE, N.D. Mr. Marion Andrews, an instructor with the Defense Threat Reduction Agency, inspects a barricaded, unused gate here April 19 during a field exercise as part of a five-day conference. More than 93 instructors and students (enlisted, officers and civilians from every branch of the military) were here for an anti-terrorism, threat-reduction conference that covered terrorist options, security operations, structural engineering and security engineering, infrastructure engineering and emergency management. (U.S. Air Force photo/Senior Airman J. Paul Croxon)