My father, his father and my father in law all saw military service. One of my wife's uncles had been a "Rat of Trobruk".
Okay, since we're talking about horrors, I was reminded of something from my childhood, so I'll share a short story. My father and all my uncles saw combat in WWII. This one uncle, let's call him uncle Joe, had been a photographer all his life. After the war he worked as the photographer for his local small town newspaper. He was the nicest, friendliest guy you could ever want to meet.
In back of his house he had this large storage space which was filled with all kinds of junk and stuff, the kind of space a little boy like me would find interesting to browse around in when I visited him. One day I was rummaging around and came across a stack of old black and white photos. Among them were several photos of severed human heads. There's one with a head propped up on a rock, another with a head on a tree stump, etc. As I'm sure you'll agree, this demands inquiry, so I asked uncle Joe "what's up with all those pictures of severed heads?" So he proceeded to tell me.
He served with the army in the Philippines. As his unit was making its way through the jungle, they were having a really bad time with Japanese snipers. The snipers were picking off their patrols, and they were very good at hiding, and the Americans couldn't ever find them.
At some point, they meet up with some indigenous Filipino natives, and the topic is brought up. Now, the Filipinos hated the Japanese for invading their islands, and they basically say "we've lived in this jungle for millennia, we know it like the back of our hand, these Japanese snipers cannot hide from us. We'll get them for you." But like any soldier, they expect to get paid.
So a price was agreed upon, I forget, I think maybe $50 per sniper killed. A day or so later, some of the natives walked into camp and said they had killed a sniper and wanted to get paid. The Americans said "Well hold on a minute, you can't just walk in here and tell us you got one. If you want to get paid we need some proof. You need to bring us a Japanese rifle or a Japanese military jacket, something like that". The natives said okay.
A day or so later, the natives walk into camp carrying the decapitated head of a Japanese man. And that's what they chose to bring back as "receipts". And the Americans would set their heads around the camp as sort of trophies.
So that explained the photos my uncle took there in the jungle. What it doesn't explain is how a man like my uncle, a sweet, good-natured gentle soul could come back from the brutality and horror of war and be a normal person.