Someone posed this question to askphilosophers.com.
You can read the philosopher’s response here. I thought the reply was interesting and I’m still pondering over it. Basically, the philosopher replied saying that military drafts in democracies should be considered mandatory. The reasoning is because if they are mandatory, then the people involved in the wars will definitely want to fight them (and will fight them) if they take the war to be just. If they feel the war isn’t just, then the people in the military will fight back. Vietnam is a good example of this. But if the military is purely voluntary, then they can’t complain because they volunteered to be in the military, whereas the people who find wars unjust can’t really fight the system because they’re not within the system to fight against the injustice itself. So instead, the people who find the war unjust can do nothing but sit idly by and watch. But over time, the people become more apathetic and don’t really care about the justice or injustices of wars.
Shaun Miller's Ideas 
I like that reasoning. United we stand, divided we fall. If we are united under the umbrella of a mandatory draft, then our interests are exactly as you specified:
just war=willing soldier
unjust war= non-compliant soldier
If our interests are uniform, we don’t get the result we got in Vietnam and are getting with the current war. The thing is, not everyone agrees what is just. For instance, if I were drafted I would be fighting jihadists with a great big ‘ol smile! You would not.
That’s an interesting point, Killer J. I think with what you said that not everyone agrees with what is just will definitely have conflicts within the military itself. Every single war has had protesters, even a small minority of them. It would be really hard to figure out an objective stance on what “just” means because we’ve been trying to figure this out since Plato.
Perhaps justice, or at least the perception of it, can change over time. Vietnam, at least when it started, was considered a just war. As the fighting continued, the perception changed where it wasn’t considered just. Why this change? My only guess is because of the social circumstances at the time.
I’m still pondering over the philosopher’s answer from askphilosophers.com. It’s an interesting concept to think about.
I even wonder if the use of “justice” as a reason for war is simply a front for enthusiasm/morale. With Vietnam and Iraq, it seems the more bleak the outlook the more cries of “injustice” are heard.
Hell, even Obama has slightly changed his tune on Iraq now that the surge is working and the outcome is not as bleak as one year ago. He went from saying we need to get out now to we need to get out, but in a responsible manner. Well, everybody wants to get out in a responsible manner. I’m sure he’s still against the war, but he seems to have changed his tune.
I wonder if he views it as more just? Only he knows, I suppose.
Maybe it’s principles. We follow principles, but if one follows them blindly, then it gets us into trouble. So if I hear “we’re staying in Iraq and I don’t care what you say.” To me, I’m thinking that’s too idealistic. Likewise, if I hear, “we’re getting out of Iraq and I don’t care what you say.” That’s also too idealistic. When it comes to politics, pragmatism is my motto.
I think after talking to advisers, Obama realized that simply getting out of Iraq, just like that, is tricky. He’ll need a plan, and not simply principles. Let’s hope the next president has one!