As the war rages in Ukraine, Vladimir Putin has threatened to launch nuclear missiles against Western cities. So far, this seems more like a bluff than a real prospect, but recent events indicate that Putin is not a completely rational actor, and a nuclear scenario should not be so easily dismissed.
If we ever reach that point, what should the West’s response be? NATO purports to operate under the principles of the “Just War” doctrine. As per this doctrine, military actions can only be justified when civilians are not targeted. That does not mean that any civilian death in a conflict should be considered a war crime. If civilians die because of collateral damage (instead of being directly targeted), this is ethically acceptable. But civilian deaths must be proportionate to the military target. If to kill one enemy soldier, ten civilians die as a result, that is not authorised by the Just War doctrine.
Nuclear weapons are so destructive that they clearly violate this principle. Even if the nuclear weapon were directed against a legitimate military target, the number of civilian deaths is likely to be extremely high, thus defeating the original moral purpose.
Morally speaking, it makes little difference who strikes first. If Russian soldiers capture Ukrainian soldiers and submit them to torture and sexual abuse, should Ukrainian soldiers do the same with captured Russian soldiers? No, they should not. Reciprocity can be an acceptable moral principle in some cases, but there are some acts that are so inherently evil, that they cannot be justified, even if the enemy did it first. To keep the moral high ground, Just War principles must be upheld, even if the enemy does not honour such principles. If we believe ourselves to be the good guys, we must act as such. The moment we become like them; it is hard to find the moral purpose to fight in the first place.
Most Just War ethicists would agree with that argument. But unlike torture or sexual abuse of captured soldiers, the use of nuclear weapons may call for some relaxation of the conventional rules of Just War doctrine. Philosopher Michael Walzer is famous for introducing the concept of “supreme emergency”. Walzer believes that when in a war we are faced with an evil of such magnitude that the only way to defeat it is by violating the very principles of Just War doctrine, we inevitably must sidestep such principles. Walzer is careful enough not to use the term “supreme emergency” lightly. In his assessment, only Nazism qualifies as the horrendous evil he is referring to, and he is prepared to excuse some questionable tactics embraced by Churchill to defeat the Nazis (most notably, the bombing of German civilians).
Putin is not Hitler, and any such comparison is cheap. The invasion of Ukraine does not warrant a supreme emergency. But if Putin attacks civilian populations with nuclear weapons, would that be a supreme emergency? In my opinion, yes it would. At that point, Putin would have to be stopped before he launches a second round of attacks, and the only way of doing so is with nuclear retaliation. Conventional military response to a nuclear attack is simply ineffectual. Any other action short of nuclear retaliation, would be unlikely to succeed in preventing further nuclear attacks. Furthermore, the devastation of the first nuclear attack would be so severe, that a clear signal must be sent indicating that should any country ever dare to launch nuclear missiles again, it will result in its own destruction.
“An eye for an eye makes the world blind” is a phrase that we commonly hear from well-meaning pacifists. To which I reply: if there is a man who goes around taking out other people’s eyes, and the only way to stop that nasty habit is to take out his own eye, then sadly, that eye ought to be taken.