Yeah, it could be the nightmares, or it could be something even simpler.
I'm not suggesting "suppressing nightmares about the war" is the reason other people drink. Just that was the reason I believe my own father drank. It's a conclusion that took me a long time to make and it's based on an analysis of the facts of his life.
If you are still struggling with addiction, maybe you don't yet have the answers you need. Maybe the pat answers you are parroting are part of the problem.
They are answers that actively promote a sense of helplessness and actively discourage pinpointing a specific cause. I'm suggesting that's exactly the problem with our current mental models.
Edit: I will also add that suppressing nightmares is about being able to sleep through the night so you can do your job the next day, not necessarily about avoiding negative feelings per se. Plenty of people take sleeping pills and are not characterized as addicts for trying to address their sleep issues so they can function.
Drinking suppresses nightmares but gives a less refreshing sleep. Must have been tough to make that choice... I wonder if he smiled less or had trouble enjoying things when he stopped... More stress or less patience. But you already shared so much about your father, you don't need to answer!
As for the sleeping pills, after I've seen how they made my grandpa dependent, and now that I'm trying to taper off antidepressants, I'd like to moderate. They probably are addicts, just not with the negative connotations of addict, if you see what I mean. I wished we'd help more people tapering off stuff.
Kudos, though, to people doing what they can to give their children and spouse a life without money worries.