A recent article in the New York Times reported that the military canines used in war zones can end up showing the same signs of stress as human soldiers.
Many people are aware of soldiers returning with PTSD (post traumatic stress disorder) but the word is just getting out that more than 5 percent of the military dogs returning have canine PTSD.
The events that cause PTSD in military dogs and humans are similar- frequent gunfire, combat-related violence, and explosions. The symptoms of canine PTSD are changes in temperament ranging from aggression (even with the handler) to extreme shyness and timidity. Well-trained dogs may stop doing the tasks they performed with great reliability before developing PTSD.
The treatment of canine PTSD is a relatively new area but the best plan of action so far seems to be removing the dog immediately from patrol and combat situations, adding very gentle (positive reinforcement based) obedience training, and providing a lot of play. For dogs who have reactions to specific stimuli, for example, the dog barks excessively when it hears a loud noise (that sounds like gunfire), systematic desensitization can be used to address the behavior.