Preventive war is wrong: Why recent attacks on Iran fail an important moral test

There is no greater spur to wrongdoing than the fear of being wronged oneself. Here we summarize the thought of Hugo Grotius, the great Dutch jurist, whose systematization of just war ethics remains a fundamental point of reference in our own day.

Grotius placed the idea of just cause at the heart of his doctrine. War inevitably causes immense damage, so those who embark on this course of action have a responsibility in conscience to assess whether it can be justified by moral principle. Only then will strategic advantage, likelihood of success, and the balance of harm over beneficial results become morally relevant. Absent a just cause, compliance with the other just war criteria – legitimate authority, last resort, proportionality, etc.– will fail to sway the moral balance. At best they will serve as mitigating factors for an action that is otherwise wrong.

Can there be just cause for purely preventive military action – action that aims to impede or destroy an adversary’s capacity to wreck future harm? To this question, Grotius responded with a resounding “no!”

True, he acknowledged, defense against ongoing or imminent attack does eminently count as a just cause, provided of course the other party has attacked first, or is about to do so. If the attack is not imminent but is merely possible at some undetermined future point in time, the same justification emphatically does not hold. It patently stands against justice to bring wrath upon a person or state that might do wrong. Retributive justice is backward looking only; it cannot, must not, be administered in advance. To think otherwise is to make fear the guiding principle in human affairs. To act on fear alone unwinds the very fabric of societal order; international anarchy is the result, and we all know where that leads.

Grotius’s predecessor, the Jesuit scholastic Francisco Suarez, spoke condemnably of the “pagan principle of preventive war”. The pagans in question were the ancient Greeks; Suarez, as did Grotius, had before him the example of Athens, as recounted in Thucydides’ famous history of the Peloponnesian war. The Spartans attacked before the Athenians’ power could become too large, while the “window of opportunity” was still open. In other words, it was fear of future harm that impelled the Spartans to initiate a war against Athens and its allies.

Thucydides considered whether this involved strategic miscalculation, while Suarez and Grotius sought to draw out the moral lessons. Netanyahu has attacked Iran preventively. He is unwilling to live with the possibility of a nuclear armed Iran, claiming this represents an “existential threat” to his nation. Apparently, Israel’s possession of nuclear arms (an open secret) is, in his eyes, an insufficient deterrent against a future nuclear attack by Iran. Israel’s attack on Tehran and other sites in Iran, both military and civilian, has been merciless. The stated justification has built on an elaborate series of “what ifs…,” but all come down to a calculus of fear.

Now the United States has joined Israel’s preventive war against Iran, with attacks against Iranian nuclear sites, including the tunnel complex under Fordo. The world awaits with bated breath to see how Iran responds. Will it abandon its nuclear program, suing for peace, or, more likely, will it safeguard its cache of enriched uranium and persist in its longstanding stance of resistance?

Whatever the outcome, these words of Grotius speak for themselves: "Quite untenable is the position, which has been maintained by some, that according to the law of nations it is right to take up arms in order to weaken a growing power which may do harm should it become too great…. That this consideration does enter into deliberations regarding war, I admit, but only on ground of utility, not of justice… That the possibility of being attacked confers the right to attack is abhorrent to every principle of equity. Human life exists under such conditions that complete security is never guaranteed to us."

Grotius’s message is clear: Fear alone offers no justification. It promises a world where the security dilemma becomes the norm; strike first before I am struck. Do we want to live in such a world?

• For more elaboration, see chapter 9 of Greg Reichberg’s Thomas on War and Peace (Cambridge University Press, 2017; a related piece can be found online published by the Vatican’s Academy of Social Sciences
• Gregory M Reichberg and Henrik Syse are Research Professors at PRIO