I remember on the show last night there was a man who was talking about hitting a German in the head and slitting his throat while he was separated from his unit and afraid(the same guy that captured 18 people with a mine detector mentioned before). It seemed to bother him terribly, even to this day. I guess when people are in a war zone, a certain level of survival instincts take over, and when you come back home, it's difficult to cope with when you think about what you had to do to stay alive.
I remember a history channel show about WWI pilots. One of them said at nearly 100 years old that he still woke up with nightmares.