Dogs have always been important to Michael White of Starkville, Miss., although he has not had one of his own in the last 50 years. Every morning, White looks at the photo of the last dog he shared his life with, Duke, the dog that possibly saved his life and many others. Duke was a military working dog during the Vietnam War. He was the property of the U.S. government with his identification number 61A6 permanently tattooed in blue ink into his right ear. Duke was issued to White, a new...