A good Article over at The Canine Bark
“Dogs have been trained to fight in our wars since ancient times, preforming tasks such as using their sense of smell to track, scout out booby traps and concealed enemies and were even used to physically bring down opponents and their horses.
Today Military Working Dogs are most commonly used as aids to police officers with larger breeds performing guard, patrol and law enforcement duties and smaller breeds performing smell detection roles, such as explosive, drug and other contraband detection.”