Coba, a 3-year-old chocolate lab and tactical explosives detector dog, chews contently on a tennis ball as David Sheffer, her handler and a dog trainer with Vohne Liche Kennels in Denver, Ind., explains the capabilities of the dog at the National Training Center on Fort Irwin, Calif. (Photo by Sgt. Christopher M. Gaylord/U.S. Army)
