“A just cause does not automatically make a just war”

Ms Fabre, you are an expert for the philosophy of just war. Let's start with the fundamentals. What is a just war, and what are its core criteria?

The idea of just war has a very long pedigree in moral, legal, and theological thought. In the West it began to take  form in the writings of Saint Augustine in the early Middle Ages. The central question it tries to answer is this: under what conditions may a political authority resort to war without acting wrongly?

Traditionally, several conditions must be met. A war must be fought for a just cause. It must be undertaken with the right intentions. It must be the option of last resort. It must stand a reasonable chance of success. And it must be proportionate to the wrong it seeks to address. These principles govern the decision to go to war and are known as jus ad bellum. Once war has begun, further principles apply, namely jus in bello. These include necessity and proportionality, as well as crucially, the principle of non-combatant immunity: while it is permissible deliberately to target enemy soldiers, it is not permissible deliberately to target non-combatants. Finally, the jus post bellum sets out the principles governing how wars must end and what constitutes a just peace.

And would you say that most states still agree to that moral framework?

Those principles are widely accepted in their general form, but deeply contested in their application and interpretation. For instance: Who counts as a non-combatant? A civilian head of state who initiates war? A factory worker producing munitions? Here is another example: some people take the view that the correct reading of the requirement of necessity prohibits the recourse to preemptive or preventive war. Others would disagree.
 

How do you view the US and Israelian attack in Iran in that context?

Reaching judgement on a conflict as it has just started is always risky. Let me confine my comments to President Trump’s defense of the war. From what we know, President Trump claims that he attacked Iran essentially so as to counter the threat posed to the United States by Iran’s nuclear development and ballistic missile programme, to prevent Iran from supporting militant groups in the region, and to bring about regime change. Of those possible justifications, the strongest one, in principle, is defence from an imminent threat. Yet, as many commentators have pointed out, no evidence has been offered to suggest that Iran was about to attack the United States. Moreover, even if removing an authoritarian regime which routinely violates the human rights of its citizens is a just cause for war in principle, it does not follow that the war is just: we have to consider whether it is proportionate, and whether it  stands a reasonable chance of succeeding. Without a clear roadmap towards a just peace, the prospects are highly dubious.   

“Claiming that a neighbour’s growing power justifies pre-emptive attack, is profoundly dangerous”

Another example for the latter would be Putin. He claims Russia's invasion of Ukraine is also self-defense against aggression: a response to an existential territorial threat through NATO. Historically, Japan justified imperial expansion as necessary to avoid being devoured by European empires. 

We need to distinguish two issues. First: what counts as aggression? On a narrow reading, aggression means direct military invasion. On a broader reading, it might include other forms of coercion. But claiming that a neighbour’s growing power justifies pre-emptive attack, is profoundly dangerous. It uses moral language in the service of military escalation and potentially imperial ambition.

So in that framework, would you say Ukraine’s self-defence is just, while Putin’s invasion is imperial aggression masked in moral language?

Ukraine’s war of self-defence clearly has a just cause. As for President Putin, it is entirely possible that he sincerely believes Russia faces an existential threat. But sincerity does not make one right. 

Especially when Russia continues to attack civil infrastructure and commit war crimes.

Exactly: proportionality and non-combatant immunity remain binding constraints. Conduct matters. But in other cases there may indeed be just causes beyond responses to military aggression. Many philosophers now agree that preventing genocide or mass atrocities can constitute a just cause for war. But even then, having a just cause does not automatically mean that war is justified all things considered.

Could you give a concrete example?

A case frequently discussed is Rwanda in 1994. Many scholars argue that had the international community intervened militarily at an earlier stage of the genocide, such an intervention would have had a just cause — namely, the prevention of mass atrocities.That does not automatically mean the intervention would have been justified all things considered. Questions of proportionality, likelihood of success, and unintended consequences would still need to be assessed. But as far as just cause is concerned, preventing genocide clearly qualifies.

In Europe, after 1945, it became a part of our proclaimed political DNA, that only self-defence against aggression is a just cause for war, that we are a soft power. But can we still afford that self-understanding in the current geopolitical moment?

Military force should always be a last resort, although what counts as last resort is contested. But I have long believed that the European Union needs its own army. Soft power alone is insufficient if Europe can no longer assume that the United States will guarantee its defence no matter what. Strategic reality has changed.

Until very recently the United States have defended acts of wars with moral arguments — even if those arguments were based on false pretenses such as with the American invasion of Iraq or possibly also right now in Iran. When Donald Trump speaks about his attack on Venezuela however, he does not even attempt to construct a complex moral framework. He openly states: We want your oil, we want dominance, strategic control,  merely adding a thin defense-rhetoric such as the so-called “war on drugs.” Are we witnessing a move away from the need to morally justify military aggression at all?

I think what you are pointing to is a shift in the scope of moral language rather than its disappearance. In earlier decades, at least rhetorically,  American interventions were often framed in universalist terms: defending democracy, protecting global security, upholding international order. Even if those claims were deeply contested or factually false, they were presented as serving broader moral purposes beyond narrow national interest. What we see now, as you suggest, appears more openly nationalist. The emphasis is on American interest, American strength, American dominance.

But even that can be morally framed. One possible argument, and I am not endorsing it, merely reconstructing it, is that American officials have a special moral obligation to their own citizens. From that perspective, prioritising national interest is not amoral; it is understood as fulfilling a duty of office. Now, to be clear, I find those arguments deeply problematic. In fact, I reject them altogether, for they unduly narrow the scope of moral concern and risk conflating power with legitimacy. But I would hesitate to say that moral language has disappeared from the United States’ - or, I should say, the Trump administration’s - rhetoric altogether.

I recently read Giuliano da Empoli’s The Hour of the Predators. He says in human history the focus on defense or attack strategies has always been cyclic. He draws on Italian Renaissance history and argues that the development of heavy artillery in the 16th century changed the strategic balance. Small republics like Florence became vulnerable. Only when defensive architecture in the form of stronger fortresses evolved - defense instead of attack became the focus again. He suggests we are entering another cycle in which aggression is rewarded — and that democracies need new “fortresses.” What do you make of that?

That is a fascinating account. It may well be that Europe is now realising that a purely reactive, wait-and-see posture is no longer prudent. The Baltic states and Finland, for instance, have intensified military preparedness. That signals awareness of vulnerability. But whether we are entering a long-term cycle where aggression dominates would require deeper analysis. 

The Canadian Prime Minister recently said at the World Economic Forum that “nostalgia is not a strategy” and that we must accept that the value-based world order is over in order to morally fight back and reestablish moral principles such as respecting territorial sovereignty of all nations and not engaging in trade wars. Do you agree with him?

I agree with him in one important sense. Among those of us who grew up after 1945 or after the end of the Cold War, there was a widespread belief that international politics, at least among major powers, had become fundamentally rule-based.

That confidence has clearly been shaken. But I would hesitate to describe the previous decades as a genuinely value-based global order in a comprehensive sense. It may have appeared that way from a Western perspective. Europe and parts of North America experienced relative stability. But many parts of the world did not.

During the decades we now nostalgically describe as an era of peace, devastating wars were unfolding in sub-Saharan Africa, in parts of the Middle East, even in Europe itself. Millions died in conflicts which rarely shook Western self-understanding.

So if there is a moral failure, it lies at least in part in the illusion that this was a universally peaceful, value-based order. It was partial. It was uneven. It was deeply entangled with power and economic interests. If we speak of defense of the world order, we must mean the whole world — not only the Global North.

In that regard there has been an intense debate about whether the West's support for Israel’s war after the massacre committed by Hamas has been just or not, or whether it reflects a different moral framework from the one we project onto other wars. How would you approach that question?

Moral consistency matters. If just war principles apply in one context, they should apply in another. Hamas has committed and continues to commit grave crimes, not only against Israelis but also against Palestinians. But I also believe that Israel has committed, and continues to commit, actions that on plausible readings of the conflict  constitute war crimes in Gaza, and serious wrongs in the West Bank.

What is deeply concerning is that neither the current Israeli government nor the leadership of Hamas appears willing to negotiate in good faith. Without that willingness, a just settlement is all but impossible. It’s a tragedy.

Cécile Fabre teaches Political Philosophy at All Souls College, Oxford. Her research interests include theories of just war, distributive justice, philosophy of democracy, ethics of foreign policy, and the moral and political philosophy of cultural heritage and espionage.