Stephen Bainbridge has a column at TCS Daily on just war and proportionality (ht: verbum ipsum). It's interesting, but it still makes use of a notion of 'proportionality' that I think misses the spirit of traditional just war theory. He says, "The proportionality prong of jus in bello requires that belligerents attain their legitimate military objectives with no greater use of force than is militarily justified and avoid disproportionate collateral damage to civilian life and property." As I noted in the comments to Lee's post on proportionality, the 'no greater use of force than is militarily justified' clause seems to me to break down into incoherence. The real heart of proportionality is not quantity of force used but our own disposition to justice. It's a part of what Aquinas calls right 'intentio', the orienting or directing of all our action only to just ends and only in ways appropriate to those ends. In reality there is no such thing as 'disproportionate collateral damage to civilian life and property', because intended collateral damage to innocents (even if only indirectly intended) is never proportionate to just ends, because it's not the kind of thing that can be rationally weighed according to principles of justice.
In fact, there is nothing intrinsically inconsistent with being proportional and using overwhelming force; you can use whatever force you please as long as you do so morally. The problem is not the force used but the type of action that 'overwhelming force' usually suggests -- recklessly endangering civilian lives, doing nothing to minimize civilian casualties, and so forth. It is the kind of action that is disproportionate to the end. Amount of force is only relevant insofar as it changes the kind of action. But it is here that Bainbridge, I think, has the right conclusion despite the faulty notion of proportionality: justice in war requires waging war justly.
