This article is not written to defend Iran. Nor is it written to rehearse familiar geopolitical arguments about nuclear proliferation, proxy militias, or the strategic vulnerability of Israel. It is written because something more serious is at stake: whether powerful states still consider themselves morally bound by limits at all.

In the early hours of 28 February 2026, Israel launched “Operation Roaring Lion,” striking Iranian military and nuclear sites across multiple cities. The United States joined shortly afterwards, with President Trump announcing “major combat operations” under what he termed “Operation Epic Fury.” Iranian retaliation followed within hours, with ballistic missiles and drones targeting Israel and American bases in the Gulf. Claims have circulated that Iran’s Supreme Leader was targeted and possibly killed, though this remains unverified.

The military facts are fluid. The moral categories are not. Under the Charter of the United Nations, the use of force is prohibited except in two circumstances: Security Council authorisation or self-defence following an armed attack. There has been no Security Council resolution. Therefore the legal defence must rest on self-defence.

The American and Israeli position is that the strikes were pre-emptive measures to dismantle nuclear and missile infrastructure before these capabilities could be deployed. This language is carefully chosen. It avoids the word “preventive.” It suggests imminence. But international law, even in its diluted modern form, does not permit war merely because another state is becoming stronger. The classical requirement for anticipatory self-defence is necessity that is “instant, overwhelming.” A speculative future danger does not suffice.

If Iran was on the brink of launching a strike, the legal case is arguable. If the operation is designed to degrade long-term capability or reshape regional power balances, then this is preventive war in substance, whatever name is given to it. Preventive war has repeatedly been justified by powerful states in the name of stability. It has also repeatedly destabilised entire regions.

The deliberate targeting of a head of state without a formally declared war further erodes the distinction between conflict and assassination. During active hostilities, leaders directing combat may be legitimate targets. Outside that context, killing the political head of a sovereign state pushes international law to breaking point. The pattern here is familiar. Law is acknowledged rhetorically and bypassed practically.

The Catechism of the Catholic Church, §§2307–2317, does not treat war as a normal instrument of policy. It begins with a presumption against violence. Section 2307 declares that “all citizens and all governments are obliged to work for the avoidance of war.” Section 2308 permits legitimate defence only under strict conditions. Section 2309 states that the damage inflicted by the aggressor must be lasting, grave, and certain; that all other means must have proved impractical or ineffective; that there must be serious prospects of success; and that the use of arms must not produce evils graver than the evil to be eliminated. These are not optional prudential suggestions. They are moral thresholds.

The Catechism does not recognise preventive war as a category. It recognises defence against aggression. The language is careful: “lasting, grave, and certain.” Capability is not the same as aggression. Suspicion is not the same as certainty. The burden of proof rests entirely on those who strike first.

If the strikes on Iran were undertaken because an attack was imminent and unavoidable, then the first criterion might be satisfied. If they were undertaken to prevent a state from becoming stronger, then the first criterion collapses. The Church does not license war to manage hypothetical futures.

Section 2312 of the Catechism insists on discrimination: non-combatants must not be targeted. Civilian casualties reported in the hundreds raise grave proportionality concerns. Even if military sites were the objective, urban bombing inevitably risks collateral harm. The Catechism explicitly condemns indiscriminate destruction of cities (§2314). Precision weapons do not eliminate moral responsibility.

Most tellingly, §2309 requires that “all other means of putting an end to it must have been shown to be impractical or ineffective.” Have diplomatic avenues truly been exhausted? Has containment demonstrably failed? Or has impatience substituted for necessity? The Catechism does not allow governments to collapse the distinction between impatience and inevitability.

The theological core remains Aquinas. In Summa Theologiae II–II, q.40, he writes:

“Causa iusta requiritur.”
A just cause is required.

He then tightens the argument:

“Bellum fit iniustum propter intentionem pravam, puta cum aliquis intendit nocere vel dominari.”
War becomes unjust because of a wicked intention, for example when someone intends to cause harm or to dominate.

Domination is explicitly condemned.

If the intention behind the strikes is strictly defensive—limited to preventing imminent catastrophe—then the moral object may be defensible. If the intention includes regime destabilisation, strategic humiliation, or demonstration of regional supremacy, then Aquinas’s warning applies directly.

There is a further Thomistic principle that modern strategists prefer to ignore:

“Non licet mala facere ut eveniant bona.”
It is not lawful to do evil that good may result.

One may not deliberately inflict grave destruction in order to secure hypothetical security. Ends do not baptise means.

If active war exists, the head of state directing hostilities may be a lawful military target. Catholic teaching does not render rulers untouchable. Yet prudence is distinct from permissibility. The killing of a leader is not merely tactical. It is symbolic annihilation. It converts limited strikes into existential humiliation. It risks martyrdom narratives. It risks power vacuums filled by more radical figures. It eliminates interlocutors. History is littered with examples of decapitation producing chaos rather than peace.

The Catechism’s requirement that the use of arms must not produce greater evils than those eliminated (§2309) applies here with force. If removing a leader increases regional instability, multiplies proxy warfare, and widens conflict, then prudence alone counsels restraint.

Iran is not an innocent regime. It funds proxies. It threatens neighbours. It pursues capabilities that destabilise the region. These facts are not imaginary. But Just War doctrine was never designed for comfortable cases. It exists precisely to restrain righteous anger and strategic convenience. The moral question is not whether Iran is hostile. It is whether the United States and Israel have satisfied the severe conditions required before killing at scale. If they have acted in genuine, proportionate, last-resort defence against imminent aggression, then the action may be licit, even without UN approval. If they have acted preventively or symbolically—if this is managerial war rather than necessary defence—then it is morally unjustifiable under both the Catechism and Aquinas.

The deeper concern is habituation. War without declaration. Targeted killing without formal hostilities. Pre-emption justified by speculation. Law cited selectively and bypassed operationally.

The Catechism begins its treatment of war with an aspiration:

“Because of the evils and injustices that all war brings with it, we must do everything reasonably possible to avoid it” (§2307).

If the most powerful states no longer feel bound by that aspiration, then the world is not entering a safer age. It is entering a more candidly violent one. And that is precisely what Just War teaching was written to prevent.