If North Korea Launches a Nuclear Attack, How Should the U.S. Respond?

North Korea’s regime has taken a bolder step in its confrontation with the United States: it has threatened to launch an attack against Guam, a US territory in the Pacific. Then, it walked it back. But, we have seen this kind of behavior in Kim Jong Un many times, so we may foresee that, sooner or later, he will again threaten to attack Hawaii, Guam, South Korea, or any other target within North Korea’s range. If such an attack takes place, and it is a nuclear attack, how should the U.S. ethically respond?

Just War Theory (the doctrine followed by most military ethicists, although by no means all of them) provides some answers. Ius ad bellum, the aspect of Just War Theory that regulates when military action can be taken, would authorize a military attack. Wars must have a just cause, and if the U.S. is attacked first by North Korea, that is a sufficiently just cause for a response.

However, the other aspect of Just War Theory, ius in bello, regulates military conduct once hostilities have begun. And, the most important requirement of ius in bello is the discrimination between civilians and combatants. The bombing of Dresden, Hiroshima and Nagasaki, are not accepted as legitimate, because they were deliberately launched against civilian populations. Ius in bello allows for civilian deaths, as long as they are only collateral damage proportional to the military objectives, and they are never directly targeted.

This ethical requirement becomes much more complex when it comes to nuclear weapons. Nuclear weapons have immense destructive power. For that reason, many Just War ethicists believe that nuclear weapons can never be morally used. Other ethicists, however, believe that nuclear weapons can indeed be used, as long as they do not target civilians. During the Cold War, theologian Paul Ramsey, for example, believed that nuclear weapons could be used against hostile Soviet military targets, but not against Soviet civilian populations. This view is very naïve, as it is foreseen that no nuclear attack could ever keep civilian casualties on a proportional limit; nuclear power is just far too destructive to maintain the proportion of collateral damage.

Taking this into account, even if North Korea attacks Guam with nuclear weapons, the US would not be morally entitled to launch a nuclear attack against North Korea. But, this also seems to be very naïve. If there is no nuclear retribution, North Korea will feel emboldened, and will probably launch a second nuclear attack on another location (presumably Seoul). If the US only attacks military targets, then North Korea will seize that opportunity by overstepping moral boundaries, while its enemy stays within the bounds of morality.

This poses an old dilemma in ethics. It’s the old debate between deontologists and consequentialists. Deontologists postulate that there are actions that are intrinsically immoral, such as deliberately attacking civilians, or for that matter, using nuclear weapons. In their view, justice must be done, even if the heavens fall. If North Korea attacks Guam with nuclear weapons, the US can strike back, but only against military targets, and never with nuclear weapons.

Consequentialists, on the other hand, believe that it is necessary to make a calculus, and consider the consequences of actions. Under this view, if the US strikes back with nuclear weapons, North Korea will not dare to attack again, the regime will collapse, and the war will end once and for all. If instead, the US follows the deontological rules of Just War Theory and refrains from using nuclear weapons, it will allow North Korea to attack again and again, and the overall death toll will be much greater. Therefore, in order to save more lives, the moral action is to strike back with nuclear weapons.

This debate is far from settled. Philosopher Michael Walzer, the most important contemporary supporter of Just War Theory, believes that in situations of “supreme emergency,” the rules of engagement can be suspended, as long as the ultimate goal is to save lives in the future. Walzer warns that this line of reasoning only applies to extreme situations. Walzer believes that only the fight against Nazism has ever represented an example of “supreme emergency”, and this justified the bombing of German civilian populations during the early phases of World War II (Walzer categorically condemns the bombing of Dresden, as this happened towards the end of the war, when Hitler’s defeat was imminent).

Under this line of reasoning, in order to avoid further attacks from North Korea (surely a “supreme emergency”, taking into account the immense destructive potential of nuclear weapons), the US would have to suspend the moral rules of war, and it would have to use nuclear weapons.

Let us suppose that, in this debate, deontologists are right, and it is never ethically acceptable to launch a nuclear attack. Would it at least be ethically acceptable to threaten with a nuclear attack? This in fact what US Presidents have done for many years: they have made it clear that, were the US attacked with nuclear weapons by North Korea, there would nuclear retaliation. This constant threatening may in fact serve as deterrence, and some historians believe that the mutual nuclear threats during the Cold War, actually kept the peace (admittedly, a very tense peace) between the US and the Soviet Union. Perhaps, then, a deontologist ethicist would never allow for the use of nuclear weapons, but she could at least allow for nuclear threats.

Paul Ramsey did not agree. He believed that the threat of committing an immoral act is immoral itself, even if the act never actually takes place. Even if a robber never actually robs a bank, the planning of that robbery is still immoral. Again, Ramsey’s view is very naïve. If the US does not make it clear that it will strike back if attacked with nuclear weapons, North Korea will feel much more at ease launching a first attack, because it does not fear a response. That is why all US Presidents for the last 30 years have made their threats very clear.

The danger, however, is that the mere threat of retaliation might not be enough. The time could come when North Korea may want to test the US’s willingness to use nuclear weapons. If North Korea attacks, and the US does not retaliate, the North Korean regime will understand that the US hast just been bluffing for all these years, and the regime will feel free to continue its attacks.

The world desperately needs a multilateral nuclear disarmament, and there is no easy way of achieving it. But, the sad truth is that, for now, threats of nuclear retaliation are needed, and in case of being attacked, the US is morally required to fulfill those threats.