Most soldiers would not say that they are joining the military to fight. They will say that they want to serve their country. Most would not say that they want to fight or kill another human being. The reason there is so much mental illness in soldiers is because their conscience said "no" to fighting. They were forced to fight because man will not do what is right in the eyes of God.
Since man will not love their neighbor as themselve (on either side of war) what are countries suppose to do? Since you can not force another country to receive the Holy Spirit and transform to be likeminded in Christ, how are we to resolve our differences? If YOU can't even talk to another christian without calling them a predator, how are YOU going to stop war?