It was being conscripted from your daily life, sent out to get get shot at, watch a bunch of friends die and get wounded, then finally your number is up and that's it.
Think about the real hell that had to be. You're senselessly shooting at people you have no real issue with. The generals and politicians make the war for young boys to go die in it. What does the American baker with a family of 5 manning the machine gun have against the German factory worker with his own family of 5? Yet they are shooting at each other. And in war, there are no target tables, health, respawns, ect. There's just people dying, and then you die.
I'm gonna do some hippie shit and analyze some images of war to show you what I mean.

What we see here is a German soldier at Stalingrad, holding a ppsh, watching the line. He's definitely a dead man and probably died shortly after the picture was taken (or he was marched to his death in Siberia). Look at the fear on his face. It's just the look of defeat. Yeah at this point maybe Germany was lost, but not from the German soldier's perspective. He looks defeated because he's already given up on getting out alive. Anyone see Band of Brothers? Remember in the 3rd episode when Lt. Spears tells Blithe you have to accept that you're already dead? Think about how fucked up of a reality that is, being forced off to the front for a war you don't personally give a damn about. Maybe you feel like you do, but you don't. The German (or whatever) government got you drummed up for the war with their propaganda. Maybe some nations, those under attack, had some legitimacy with doing it, but I'm not claiming all war is always wrong. I'm just trying to show how fucked up it really is.

It's hard for me to bear looking at this one. When we remove all context, we have one human being exercising control over a fellow starving human being at gunpoint. The prisoner is starving and freezing but the guard is smirking that revenge is being enacted on the German. What do either of them care about each other? Nothing really. They're just following orders.
Why do we celebrate war then?