“There is indeed a doctrine of “proportionality” in the law of war (leaving aside for the moment all arguments about the moral and legal status of such international law). However, the concept as invoked by the media and by unfriendly or mendacious leaders is not at all that the casualties inflicted by the side responding must approximate those inflicted by the side attacking, or vice versa. The meaning of the doctrine is that (1) the force used and casualties inflicted must not be disproportionate (implicitly “grossly disproportionate”) to what is necessary to accomplish the military objective at the least cost to oneself and (2) the cost necessary to achieve the military objective not be grossly disproportionate to its military value. Thus, for example, you cannot destroy an entire town to eliminate one building that contains enemy combatants if you can relatively cheaply simply destroy that building. Nor can you destroy an entire town merely to eliminate a building containing six combatants even where you have no other means of doing so (unless for some strange reason the six combatants are of surpassing military importance).

Nothing about the doctrine of proportionality, properly understood, bears on Israel’s response to Hamas rockets. Israel has an absolute right, enshrined in the UN Charter, to defend itself against such attacks without need of any Security Council authorization, and defending means, not “proportionate” retaliation, but the actions necessary to eliminate the attacks. Indeed, absolutely contra the notions of such as Sarkozy, retaliation purely for its own sake, to inflict damage solely as punishment, would be prohibited as non-defensive. Only actions rationally intended to eliminate the attacks would be legitimate self-defense. On the other hand, in defending against such attacks, one is entitled to use such force as is necessary to end them. Thus, if the Israeli actions, rationally intended to end the willingness and/or ability of Hamas to continue its rocket attacks, are not sufficient to end them, the force being used is not only not disproportionate, it is insufficient.

It is a terribly painful position for Israel to be in, knowing that force sufficient to end Hamas’ attacks will be subject to vicious international criticism. But that is probably still better than using insufficient force and enduring much the same criticism without achieving the outcome. Doing what is necessary, at least cost to itself, in a completely unambiguous effort not to achieve some particular political outcome but to stop the attacks would at least have the advantage of being sanctioned by law, even if many hostile nations would choose publicly to deny it. They know that no nation is under an obligation to allow itself to be attacked and no nation with the means to defend itself would allow itself to be attacked in this manner.. The US inflicts far more civilian casualties in Iraq, Afghanistan, and Pakistan for less reason. There is language with which this can be pointed out without casting the US as merely an even greater villain. In war, there are civilian casualties. They should be minimized but are not the basis for compromising the achievement legitimate military objectives, not now, not ever. There is not and has never been any such law of war.”

http://blogs.tnr.com/tnr/blogs/the_spine/archive/2008/12/27/very-disproportionate-indeed.aspx#comments