Obviously firing loud weapons or being around them is flat out. But there are all sorts of jobs available in the military branches. When Vietnam was raging and some of my friends were being drafted right after graduating from high school (and some not coming back either, along w/ their fathers) I called my uncle Ralph. He was a brainy guy who had retired from the Air Force. The first thing he said was, this was a "war" where I didn't want to be on the ground.
That made sense, so I went to the local Air Force recruiter. Took the tests and all, and they said they would send me up to Chanute, Illinois to learn to be an X-ray tech. But I was a Southerner, and figured those Illinois winters would kill me as surely as any enemy. Not long after that, the US left Vietnam in a highly questionable manner and my need to go into the military was reduced to zero.
Two things to remember about any military branch though. First, you better like taking orders. That was the other deal killer for me. Most Southerners will NOT follow orders, it's drilled into us from birth, we're just rebellious and individualistic, and won't be bossed around. So that part was never going to work anyway.
The second thing is, you could easily find yourself on a battlefield even if you think it's not a just war. Sure, you can just quit, but the repercussions will probably follow you around the rest of your life and you will be punished. Just voicing your opinion about that is not gonna work w/ the military chain of command, even if it is obvious you are right. There are many, many other ways to serve our country and humanity. But the military does pay well now, you can retire (assuming you're still alive) at an early age, they can teach you marketable skills, all that.
Just depends on what you want, and what you're willing to sacrifice to get it I suppose.