I’ll give you another example of how that does not hold true.
Someone I used to work with joined up. I saw him a few years later, he had been home from Iraq just about 6 months. He was depressed, suicidal, told me awful stories about things he witnessed there and things he did there. One of which included torturing a 14 year old boy by exploding bullets between his fingers. When he refused, at first, to do it, his sergeant held a gun to his head.
When I asked him why he joined up, he said…….”I wanted to be able to kill people legally, among other things.”
I do not believe that everyone or even the majority of everyone who goes into the military feel this way. But this man did.
Of course he said that now he has no wish to kill anyone but himself.