Are the US-Israel strikes on Iran a 'just war'?

Christian Just War theory represents one of the most influential ethical traditions for evaluating the moral legitimacy of warfare.

Developed within Christian theology but later influencing secular international ethics and law, the theory attempts to reconcile two competing commitments: the Christian call to peace; and the moral responsibility of political authorities to protect the innocent and oppose those threatening harm to others.

In the context of the 2026 military attack by the United States and Israel on Iran, Just War theory provides a framework through which the morality of the conflict can be evaluated. While some arguments suggest that the intervention could be justified as an act of self-defence against a serious security threat, other considerations – particularly regarding the criteria of last resort, proportionality, and civilian harm – raise significant doubts about whether the war meets the classical standards of a "Just War" in Christian ethical terms.

The origins of the 'Just War' concept

The origins of Christian Just War theory lie primarily in the writings of Augustine of Hippo in the fourth and fifth centuries, and the concept was later developed systematically by Thomas Aquinas in the 13th century.

Augustine rejected the view that all violence is inherently immoral, arguing instead that war can sometimes be morally permissible if undertaken to restrain evil and restore peace.

Aquinas later formalised this reasoning by identifying specific criteria that must be satisfied for a war to be morally legitimate. These principles eventually developed into two major categories known as: jus ad bellum, which concerns the justice of going to war, and jus in bello, which governs the moral conduct of warfare itself.

The criteria of jus ad bellum traditionally include six conditions:

• First is just cause, meaning that war must respond to a grave moral wrong such as aggression, invasion, or severe injustice. The most widely accepted just cause is the defence of innocent life against attack.
• Second is legitimate authority: Only properly constituted political authorities may declare war on behalf of a political community.
• Third is right intention, which requires that the purpose of the war be the restoration of justice and peace rather than revenge, conquest, or economic gain.
• Fourth is last resort, meaning that all reasonable diplomatic and non-violent alternatives must have been attempted before military force is used.
• Fifth is probability of success: a war that has no realistic chance of achieving its just objectives is considered morally irresponsible because it sacrifices lives without meaningful purpose.
• Finally, proportionality requires that the anticipated benefits of war outweigh the harm likely to be caused by the conflict.

Even if these conditions are satisfied, Just War theory imposes further restrictions on how war may be fought under jus in bello. Two central principles govern the conduct of warfare:

• The first is discrimination, sometimes called non-combatant immunity, which requires that military forces distinguish between combatants and civilians and avoid intentionally targeting the latter.
• The second is proportionality in the use of force, which prohibits excessive or indiscriminate violence relative to the military objective being pursued.

Applying these standards to the current conflict

Applying these principles to the 2026 US–Israeli attack on Iran produces a complex and contested ethical assessment.

'For'

Advocates of the intervention may argue that the war satisfies the criterion of "just cause" if it is interpreted as an act of legitimate self-defence. Israel has long perceived Iran’s nuclear programme and ballistic missile capabilities as an existential threat. If intelligence assessments indicated that Iran was approaching nuclear weapons capability or preparing hostile actions against Israel or American forces, proponents might claim that military action was necessary to prevent catastrophic harm. Within some interpretations of Just War theory, anticipatory self-defence can be morally permissible when an attack is imminent. Under this view, striking Iranian nuclear facilities or military infrastructure could be justified as a defensive measure intended to protect millions of civilians from potential nuclear or large-scale missile attacks.

Supporters might also argue that the intervention was justified as a defence of allies and regional stability. The United States maintains extensive military commitments throughout the Middle East, and Iranian military activity or support for armed groups hostile to Israel and American interests (Hezbollah in Lebanon, the Houthis in Yemen, Hamas in Gaza being the main examples) has constituted a persistent threat. If the strikes were intended to deter or neutralise military capabilities perceived to endanger regional security, proponents might claim that the intervention aimed to restore stability, and to prevent a larger future (nuclear) conflict.

Another argument advanced by some defenders of the current military intervention is the possibility that removing or weakening a repressive regime may contribute to justice and human rights. Iran’s government has a long track record of suppressing political dissent and restricting civil liberties. This has been bloodily demonstrated in late 2025/early 2026 by its killing of huge numbers of those protesting against the repressive nature of the regime. This has added to a long record of brutally repressing dissent, persecuting and killing women who challenge the regime’s discriminatory and controlling policies, and denying democratic expression. Although "regime change" is not traditionally a primary justification in classical Just War theory, some contemporary ethicists have suggested that humanitarian considerations may, in certain circumstances, strengthen the moral case for intervention.

'Against'

Despite these arguments, however, substantial objections arise when the conflict is examined through the same ethical framework. The most significant concern relates to whether the war genuinely satisfies the requirement of "just cause".

Critics argue that, while Iran may have posed a long-term strategic threat, there is little available evidence that it was about to launch an immediate attack that would justify pre-emptive military action.

The US had earlier claimed that it and Israel had obliterated Iranian nuclear capability during the 2025 "12 Days War". Classical Just War reasoning generally requires that the threat be imminent and grave; otherwise military action risks becoming preventive war, which many Christian ethicists regard as morally problematic.

Closely related to this concern is the principle of "last resort". Just War theory insists that war should only occur after all reasonable diplomatic avenues have been exhausted. As negotiations regarding Iran’s nuclear programme and regional security arrangements were still ongoing at the time of the strikes, it can be argued that the decision to resort to military force was premature. The ethical legitimacy of the war therefore depends heavily on whether policymakers reasonably believed that diplomacy had failed or whether viable non-violent alternatives remained available. Many would argue that the latter remained feasible, despite the intransigence of the Iranian regime.

Questions also arise concerning "right intention". If the primary aim of the current intervention was not simply to prevent an imminent threat but to weaken or overthrow the Iranian government, critics would argue that the war pursued broader geopolitical objectives rather than the restoration of justice.

Within Christian Just War thought, motivations such as domination, revenge, or political transformation of another state are generally regarded as ethically suspect. To this can be added the deliberate assassination of a national leader (however appalling the track record of His regime) and the precedent this sets to other global state actors.

Given the terrible nature of the repressive Iranian regime, this is a difficult issue but its potential for the wider application of such targeted lethal force (with attendant destabilising effects on the global rules-based order) should give cause for concern.

Concerns about "proportionality" and the conduct of war further complicate the moral evaluation. Military strikes against nuclear facilities, military installations, and leadership targets may be considered legitimate military objectives. However, if the conflict results in significant civilian casualties or the destruction of essential infrastructure, the war may violate the principles of discrimination and proportionality under jus in bello.

Modern warfare often involves complex urban environments in which civilian harm is difficult to avoid, but Just War theory nonetheless requires that all feasible precautions be taken to minimise such damage.

Finally, the broader consequences of the war raise questions about proportionality at the strategic level. If the intervention triggers regional escalation, destabilises neighbouring countries, leads to prolonged conflict, and destabilises the global economy (as oil flow through the Straits of Hormuz is disrupted) the overall harm produced by the war may exceed the immediate harm it was intended to prevent.

Just War theory therefore requires not only an assessment of immediate military objectives but also a realistic evaluation of the long-term consequences of military action. The latter are far from clear in the current conflict.

Overall, the absence of any attempt to bring the matter before the UN Security Council or the UN General Assembly (seeking their support for this military action) means that there is no internationally recognised legal basis for the current war. This severely weakens the war’s status of being waged by “legitimate authority”, as required by the second condition of jus ad bellum (outlined above). On that basis, it can be argued strongly that it is an illegal war. Whatever the problems with the current rules-based order, this flouting of the legitimacy of that “order” sends a signal to other states, such as Russia and China, that should cause concern to all who value legality among nations. Just War does not allow for “Might makes Right”.

Concluding evaluation

The situation is a difficult one. When the criteria of Christian Just War theory are applied collectively, the 2026 US–Israeli attack on Iran appears difficult to justify fully within the classical framework.

While a plausible argument can be made that the intervention aimed to neutralise a serious security threat, the moral legitimacy of the war ultimately depends on the degree to which that threat was both imminent and unavoidable.

If Iran posed an immediate and credible danger that could not be addressed through diplomatic means, then a limited defensive strike might satisfy the requirement of "just cause". However, if the threat was primarily long-term, the justification for initiating war becomes significantly weaker.

Equally important are the principles of "last resort" and "proportionality". Just War theory places a strong presumption against the use of military force, requiring clear evidence that diplomatic and political solutions have been exhausted. Without such evidence, the decision to resort to war risks violating one of the central moral safeguards within the tradition. It also further undermines the – already shaky – global rules-based order, that has been challenged by the Trump administration’s previous behaviour in a number of areas. What if China applied the same logic of its national self-interest to Taiwan? Furthermore, it is likely to cause North Korea to accelerate its development of nuclear weapons, in order to deter possible US action against it. Within a week of the US-Israeli attack on Iran, North Korea successfully test fired a sea-to-surface strategic cruise missile. North Korea uses the term “strategic”, when referring to its missile systems, in order to indicate that they have nuclear warhead capability. While the date of the latest test was, no doubt, fixed prior to the US-Israeli attack on Iran, the potential of that attack to escalate nuclear proliferation (rather than deterring it) is all too clear.

Moreover, the potential for civilian casualties, regional escalation, and prolonged instability raises serious concerns about whether the harms produced by the war are proportionate to the threat it sought to address.

Further concerns are raised by the dubious apocalyptic end-times views concerning actions in the Middle East that are traditionally promulgated by the most extreme of Trump’s supporters within the US Evangelical right. These hardly serve to encourage confidence in the rationality of the arguments for military action being presented to this most mercurial of US presidents.

There is a very real danger that – with Iran greatly weakened, over the past two years, by the degrading of its proxies Hezbollah in Lebanon, Hamas in Gaza, the Houthis in Yemen, Assad gone in Syria, and itself significantly damaged by last year's "12 Days War" – the US and Israel have decided to cripple the regime, with no clear path towards a viable end-game.

Iran has a multi-ethnic population of over 90 million. If the result of the current war is prolonged civil war, it has the potential to be far greater than the terrible conflicts that occurred in Iraq after 2003 (including the appearance of ISIS), in Syria after 2011, and in Libya (now a conduit for migrants north to Europe) after the fall of Gaddafi in 2011.

An Iranian civil war could cause a flood of displaced persons far greater than these earlier conflicts did. These earlier conflicts added greatly to a surge in refugees/asylum seekers, which has had huge consequences for Middle Eastern and European politics in the years since. Iran could cause a worse refugee crisis.

"No plan survives first contact with the enemy," is the military maxim of 19th-century Prussian Field Marshal Helmuth von Moltke. But that assumes that there is, at least, "a plan". At present, that seems far from certain in this joint US-Israeli action.

For these reasons, although some elements of the current war could be interpreted as consistent with defensive reasoning, the available evidence suggests that the war struggles to satisfy several of the most demanding criteria of Christian Just War theory.

From an ethical perspective, grounded in the classical tradition, the conflict cannot be regarded as a clear example of a "just war", but instead as a morally ambiguous or potentially unjustified use of force. Such a conclusion does not deny the reality of genuine security threats posed by the Iranian regime in international politics, or the terrible nature of the Iranian regime, but it reflects the stringent moral limits that Christian Just War theory seeks to impose on the resort to violence in the pursuit of peace.

Despite the claims of Trump to represent a Christian force in US and global politics, it is difficult to imagine that this consideration has weighed heavily on the mind of the US president.