The previous points in node, while argued passionately and with reason, force me to drop in a few of my own. Note: I do not, and have not, served in the military. I want to make this clear at the outset. I argue the following as an American Citizen, one who has devoted fair amount of time to studying war, the men and women who fight them, and the tools they use.

While I agree with much of what pihwlook says above, I would add that in fact, most of the time, the soldier is not killing "at the order of the old guy in Washington." The pilot isn't strafing an anti-aircraft position because he or she is following a grand scheme order. The sailor isn't setting up a torpedo run on an enemy vessel because he or she has been told to do that by Washington. The nearly unanimous opinion of those I've bothered with questions about this is this: "I do/did/will do it because if I don't, I and/or the guy next to me will most likely die."

While armies and navies enter engagements at the orders of their distant commanders, individual combatants typically perform their daily duties driven by self-preservation and loyalty to 'their own' which has been inculcated in them via stringent and practiced techniques.

There are many issues involved with 'being a soldier.' Why are you there? On one hand, maybe because you needed college tuition. On another, maybe because a judge told you to go. The guy next to you may be there because it's a family tradition. The woman across the table may be there because of a desire to prove she can defend her country as well as anyone. Your seatmate in the bus may be there for deep-seated idealistic reasons.

Why are you fighting? Typically, in the moment of combat, you're not doing it on orders, you're doing it for the reasons above. The problem, here, is that (with some notable exceptions) the orders from above usually just put the soldier in harm's way. The proximate cause of each violent incident ranges from the idealistic to the completely silly.

This is relevant because we need to remember, when 'judging' soldiers (and I, for one, don't believe for a moment that those of us who have not served should judge them for what they do as a job) that it's very unclear why they do what they do in both the macro and micro scale. If you must discuss their volitional culpability, I would say that barring criminal behavior/orders, the last time you can really say a person was making their own choice in the matter was when they signed the form.

From the moment you arrive in the military, you are confronted with a cadre of skilled professionals whose entire job is to ensure that you fight when told, respond the way they want you to (which, while counter to personal survival instinct, usually serves a group good). From that point on, it's difficult to discuss the soldier as a wholly voluntary actor.