Suppose a powerful nation unjustly invades its weaker neighbor. International law is clear: this is aggression, and the victim nation has the right to individual and collective self-defense. That is, the victim of aggression has the right to defend itself and to seek help from other nations. Article 51 of the UN Charter makes this right virtually unconditional and absolute: “Nothing in the present Charter shall impair the inherent right of individual or collective self-defense if an armed attack occurs against a Member of the United Nations.”
Philosophers have in turn developed a body of rules to evaluate war: Just War Theory (JWT). JWT is richer and more complex than the bare rules of international law. It proposes a list of conditions that any war must satisfy to be justified. Writers vary in the formulation, but most of them would endorse the following list:
1) The belligerent must have a just cause.
2) The belligerent must abide by ius in bello (the laws of war).
3) The war must have reasonable chances of success.
4) The war must be proportionate, that is, the expected damage should not outweigh the realization of the just cause.
In our example, a defensive war by the victim of the aggression has a just cause, so it complies with condition 1. Let’s assume that it can also comply with ius in bello, condition 2.
But the defensive war cannot possibly comply with conditions 3 and 4. The defensive war has no reasonable chances of success. Can it be proportionate? No, if we compare the decision to fight with the decision to submit to the aggressor. Say that fighting will predictably cost 10000 innocent lives for naught (since the war is doomed to failure), while submitting to the aggressor will save those lives. Or worse: suppose the victim, exercising its right under article 51, asks its powerful allies to assist it in countering the aggression. This will predictably escalate the conflict, kill hundreds of thousands, and cause devastation of all sorts. Even if the allies' help will increase chances of victory, under JWT the defensive war will be likely disproportionate.
It seems then that under Just War Theory the victim nation must submit to the aggressor. But that sounds bad, to say the least. We instinctively feel that the victim of the aggression has the right to resist no matter what, as international law says. Maybe the attacked nation reasonably expects to impose a heavy price on the aggressor. This, of course, is not enough to satisfy JWT’s success condition: imposing a heavy cost is not the same as winning. And choosing to bring about the deaths of 10000 innocents, or worse, triggering a regional conflict, when the attacked nation had the option to submit and avoid those dire consequences, cannot possibly satisfy proportionality.
Who is right? The UN Charter, which allows nations to resist aggression regardless of cost? Or Just War Theory, which indicates the opposite?
It seems hard to resist the logic of Just War Theory. If resisting leads to a catastrophe, perhaps submission is mandatory. On the other hand, perhaps sometimes fighting is the right thing to do, even against the odds (think of Churchill circa 1940). And at any rate, the success and proportionality conditions in many cases favor aggressors. This suggests that the theory of justified national self-defense must be revised. One way to start is to relax the success condition and add qualitative considerations to the calculus of proportionality.