[cjg]

One would hope that soldiers who had some experience in mindfulness would begin to notice their discomfort at killing other human beings.

[UnFleshedOne]

That's hippie talk. :) As another commenter pointed out, mindfullness and meditation was long used for martial arts training.

There is nothing in the core practice itself that leads to pacifism (or belligerence). It might even make easier to ignore that discomfort, like any other, if you have mental tools.