Yes, most definitely. Surprisingly a lot of the lads I served with (British Army 1999-2008) say they found the dehumanising effect of training to be the thing that has left the most traumatic mark on them. Deployments are gash, but the training (initial and ongoing) sticks even harder in my opinion.
When you're in basic (and phase 2, of course), a large portion of that training is aimed at getting you to obey orders, immediately, without question, always, and also what's known as "removing the barrier to kill."
I won't go into the science (post WWII) that played a part in shaping the training of a modern soldier, but studies showed that only a small percentage of soldiers were shooting to kill - historically. So military leaders, scientists/psychologists were employed to find ways to push that percentage up.
I'll give some examples of things that get used in training to remove the barrier to kill, some may sound familiar;
"Aim for the centre of mass"
Not "shoot the bloke, kill the bloke, etc etc
Reducing your victim to that is a technique used in removing the barrier to kill.
How about this for another;
"Targets will fall when hit"
Just two examples. By drilling this into recruits over and over and over, you are producing a certain effect, a desired one.
Other little choice tactics of the DS in training was to shout "corridor" - that meant you all dropped whatever you were doing and got into the corridor, backs to the wall, stood to attention (until told otherwise) - this was usually for briefings or so on. If someone answered back, even just a simple acknowledgment that they were on their way, or anything really, you'd get told to assume one of two positions; arms up (like a surrender gesture) or "chins out", at which point the DS (usually a Corporal) would walk down the line and either punch you in the side of the face, or punch you in the gut - and not half arsedly either. I'm not exaggerating, and some of those little s***TS clearly enjoyed it. I eventually worked up the ranks a little, and I am sickened to say I was no better.
Here's some other things. In training we were taught that our first loyalty was to our unit, that all other units were inferior to ours, and to hate them, but above all we were told to hate civilians. As Ben Griffin rightly said in a video; "we used to call them civvie c**ts" (pardon the language). People who didn't have the guts to serve (or so we were drilled to feel) or who couldn't get in because of medical reasons etc.
Now, think about it, if you can get your blokes to hate their own civilian population, imagine what you can get them to do to the civilians of someone else's country?
Then there is the fact that the manner in which you're returned to civilian life isn't as phased and calculated as your uploading to the forces. To my mind, apart from the resettlement courses and what-not, it's a pretty cut and shut thing.
I served on deployments, and now I totally, totally regret it. It's shaped me for the worse (maybe less so now, but badly at first). I joined an organisation which speaks out about this sort of stuff after I left, and I'll not even lie and say I got out of the armed forces on good terms - I didn't and what's more I don't care that I did.
I wish I'd never joined.
Again, an emphatic yes, joining the forces played a part in screwing up who or what I am. It's not the only thing or the biggest factor that's made my mind work the way it goes these days, but it's definitely a contributing factor. There isn't anything brave or noble about invading someone else's country and so on, and I'll have to square myself away with that for the rest of my life, however long or short it may be.