When Intervention Is Justified … or Not

Quadrant

Editorial note: An earlier version of this essay was first published in Quadrant on 23 January 2026. Reader feedback prompted a structural revision: the original introduced the concept of enlightened self-interest but did not carry it through the analysis. This version uses it as the organising principle throughout.

Events in Iran provide a useful lens through which to assess the arguments advanced here. As this revision goes to press, two American carrier strike groups are converging on the Persian Gulf. President Trump has given Iran ten to fifteen days to agree to a nuclear deal – or face consequences. Iran is a harder case than Venezuela, and may even be a justified one. But if intervention is to be in America’s enlightened self‑interest, the conditions must be genuinely met – not manufactured, not accelerated by domestic political need, and not driven by one leader’s unchecked impulse.

“If not military intervention, then what? And when is intervention justified?” Those were the challenges from readers of a recent essay arguing conservatives should not be too quick to praise President Trump’s removal of Venezuelan dictator Nicolás Maduro.

My objection was not that Maduro did not deserve his fate – he did. It was that methods matter. The Venezuela operation was unilateral, without congressional authorisation or allied support. Its justification was openly transactional – oil, drugs, the Monroe Doctrine. There was no plan for what follows. The historian Niall Ferguson, writing in The Free Press, praised Trump as a “nineteenth-century figure” returning to the politics of 1900. But that is not a compliment. The politics of 1900 produced 1914, and then 1945. A rerun with nuclear weapons will be worse.

It is easy to say “not like this.” It is harder to say when intervention is justified – and why.

“If not military intervention, then what? And when is intervention justified?” Those were the challenges from readers of a recent essay arguing conservatives should not be too quick to praise President Trump’s removal of Venezuelan dictator Nicolás Maduro.

My objection was not that Maduro did not deserve his fate – he did. It was that methods matter. The Venezuela operation was unilateral, without congressional authorisation or allied support. Its justification was openly transactional – oil, drugs, the Monroe Doctrine. There was no plan for what follows. The historian Niall Ferguson, writing in The Free Press, praised Trump as a “nineteenth-century figure” returning to the politics of 1900. But that is not a compliment. The politics of 1900 produced 1914, and then 1945. A rerun with nuclear weapons will be worse.

It is easy to say “not like this.” It is harder to say when intervention is justified – and why.

Under international law, the use of force is permitted only in self-defence against armed attack, or with authorisation from the UN Security Council. There is no general right to invade another country – even to protect its civilians from their own government. That prohibition has been violated often enough — from Hungary in 1956 to Crimea in 2014. But a rule that is sometimes broken is not the same as no rule at all. The question is whether, and when, exceptions can be justified.

Trump has made the question urgent. Venezuela was not a one-off. Trump has already warned Cuba to “make a deal before it’s too late.” Colombia has been threatened over drug policy. And European allies now face escalating tariff threats designed to force Denmark to cede Greenland to the United States – with the president linking his demands, in part, to having been denied the Nobel Peace Prize. The “Donroe Doctrine,” as Trump styles it, is the announcement that the Western Hemisphere is America’s sphere of influence, where Washington decides which governments are acceptable and removes those that are not.

This essay attempts an answer. Not a complete theory of humanitarian intervention, but a framework for thinking about the question – one grounded in a single idea that has been missing from the conservative debate.

Enlightened Self-Interest

Implicit in the question of when to intervene is the question of why. The narrow answer is: only when it serves the national interest. Dwight Eisenhower gave a better one when he argued for American leadership of NATO in 1951. He called it ‘enlightened self-interest’ – the recognition that American security depended on European stability, and European stability depended on American commitment. The costs of engagement were real. The costs of withdrawal would be greater.

The key word is enlightened. It has two dimensions. The first is systemic. Narrow self-interest asks: what serves my power now? Enlightened self-interest asks: what sustains the order that serves me over time? That is a genuinely different question, and it yields different answers. A leader acting on narrow self-interest can justify unilateral action whenever it delivers an immediate gain. A leader guided by enlightened self-interest cannot – because unilateral action undermines the system of mutual constraint that serves everyone’s long-term security, including America’s.

The second dimension is moral. The concentric circles of moral obligation do not stop at the border. They thin as they extend outward – from family to community to nation to humanity – but they do not vanish entirely. The case for intervention rests on both pillars: the defence of an international order that serves the security of liberal democracies, and the recognition that human suffering matters – particularly on a mass scale, and especially when it occurs in regions with which those democracies are deeply entangled by history or values.

Enlightened self-interest has limits. It explains why Western democracies intervened in Kosovo, where instability in the Balkans threatened European security, and why they did not act in Rwanda, where the strategic stakes were lower and the concentric circles of moral obligation had thinned. But it does not excuse the result. Eight hundred thousand people died. The obligation had not reached zero – it had merely fallen below the threshold that produced action. Most Western leaders later called Rwanda a failure, not a success. That discomfort is the point. A framework grounded in enlightened self-interest will not demand intervention everywhere. But it should never be comfortable with inaction in the face of genocide. That residual discomfort – the recognition that moral obligation persists even where strategic interests do not compel action – is precisely what distinguishes this account from naked self-interest.

But enlightened self-interest is not naïveté about costs. Modern history offers ample evidence that even well-intentioned interventions can harden resistance, prolong conflict, and impose burdens that far outlast the original justification. Vietnam, Iraq, Afghanistan, and Libya differ in context and cause, but they share a lesson: once force is used, control over outcomes is quickly lost. The risks of acting fall not only on those intervened against, but on the interveners themselves – and on the order they are trying to protect. That is precisely why prudential thresholds must be high, and why frameworks matter.

Three Conservative Positions – and What Is Missing

Eisenhower was a Republican president and Supreme Allied Commander. But his insight has no obvious heirs in today's conservative landscape. Rather, three positions dominate conservative thinking on military intervention. Yet, measured against the standard of enlightened self-interest, each falls short.

The first is realism. John Mearsheimer and his disciples view humanitarian justifications as window dressing for great-power competition. States pursue interests, not principles. The rules-based order was always a fiction maintained by American hegemony, and now that hegemony is fraying. This diagnosis has force. But realism sees only narrow interests. It does not recognise that maintaining the order is itself an interest – that the system of rules and alliances built after 1945 delivers security returns that no amount of unilateral power can replicate. Nor does it accept that the concentric circles of moral obligation are genuine. For the realist, states act from interest and humanitarian motives are always pretence. Enlightened self-interest disagrees on both counts – and because realism denies both, it has no criteria for the cases where intervention might be necessary.

The second position is neoconservative interventionism. In 1996, William Kristol and Robert Kagan called for a ‘neo-Reaganite foreign policy’ based on ‘benevolent global hegemony.’ American power was good for America and good for the world. The United States should use that power confidently to promote democracy and confront hostile regimes. This vision animated much of the Bush administration’s foreign policy, culminating in Iraq. Neoconservatives grasped something the realists missed: that the liberal order matters and is worth defending. But they offered no limiting principles. Their framework could justify almost anything – and Iraq showed what happens when enthusiasm outruns constraint. Unconstrained interventionism destabilises the very order it claims to defend.

The third position is Trumpian transactionalism. This dispenses with both realist caution and neoconservative idealism. Trump does not pretend to be spreading democracy. He does not invoke humanitarian principles. He simply asserts American power in pursuit of immediate American interests, openly and without apology. Ferguson finds this ‘refreshingly honest’ compared to the hypocrisy of liberal internationalism. But honesty about abandoning principles is not a virtue. Transactionalism is the narrowest possible conception of self-interest – the opposite of Eisenhower’s insight. ‘We intervene when we want to’ is not a framework. It is the absence of one. And it actively dismantles the order that serves American security.

What is missing from this landscape is a classical liberal account – one grounded in enlightened self-interest, that takes seriously both the case for intervention and the case for constraint. Classical liberals are not pacifists. They recognise that force is sometimes necessary to defend the conditions under which free societies can flourish. But they also understand that unconstrained power is dangerous – whether exercised at home or abroad. That is the entire case for limited government, separation of powers, and the rule of law. The same logic applies to the international order.

A Framework for Justified Intervention

The question of when military intervention is justified is not new. The just war tradition runs from Thomas Aquinas through to Michael Walzer. But the starting point for any modern answer is the post-1945 settlement. Under international law, there is no general right to invade another country – even to protect its civilians from their own government.

After the Cold War, atrocities in Bosnia, Rwanda and Kosovo exposed the gap between that prohibition and the moral revulsion democracies felt at mass killing. States were intervening anyway – often in ad hoc coalitions and with contested legality – yet without any agreed standard for when force might be justified.

In 2001, the International Commission on Intervention and State Sovereignty sought to develop a principled exception. The Commission developed what became known as the Responsibility to Protect. R2P was adopted by the UN General Assembly in 2005 and remains part of the international vocabulary.

R2P sets out six criteria: just cause (large-scale loss of life or ethnic cleansing), right authority (Security Council authorisation or, failing that, General Assembly or regional bodies), right intention (the primary purpose must be to halt suffering), last resort (diplomatic options must be exhausted), proportional means (the scale of intervention must match the objective), and reasonable prospects of success (intervention should not make things worse).

These criteria represent the distilled wisdom of centuries of thinking about the morality of war. They are also, viewed through the lens of enlightened self-interest, intensely practical. Each one serves to protect the international order from exploitation. Just cause prevents adventurism. Right authority prevents sphere-of-influence politics. Proportional means limits escalation. Reasonable prospects guard against the failed states and power vacuums that destabilise entire regions. The criteria are not merely moral aspirations. They are structural protections for the system that keeps democracies safe.

The problem is not the principles but the machinery designed to apply them.

The first problem is institutional. R2P channels intervention through the UN Security Council, which is now paralysed by great-power rivalry. Russia and China will veto anything that resembles Western regime change after the Libya intervention in 2011, which they saw as a bait-and-switch – authorised to protect civilians, used to topple Gaddafi. The Security Council route is blocked, and it is not coming unblocked.

The second problem is political. R2P has been championed primarily by liberal internationalists, wrapped in UN-centric language that alienates conservatives and leaves the centre-right without a framework of its own. If the only vocabulary for justified intervention is the vocabulary of the UN, then those who distrust the UN have no vocabulary at all – and default to either paralysis or raw assertion of power.

What follows is not a rejection of R2P but an adaptation of it – a framework for a world in which the Security Council cannot function as gatekeeper. It keeps what R2P gets right and adjusts what no longer works, grounding each criterion in the logic of enlightened self-interest.

Just cause remains essential. There must be an ongoing atrocity, not merely bad governance. Genocide, ethnic cleansing, mass atrocities in real time. The intervention aims to stop killing that is happening, not to punish past misrule or secure resources. This is a high threshold – and should be. Plenty of regimes are brutal, corrupt and authoritarian. That does not make them legitimate targets for military action. A low threshold would invite the adventurism that destroys the order. There are slow-motion catastrophes – like Venezuela’s collapse – that inflict enormous suffering but do not meet this threshold. That is precisely why they are not obvious candidates for military intervention.

Right authority needs revision. If the Security Council is blocked, the alternative is not unilateral action but collective action among democracies, arrived at through deliberation. Nineteen NATO members debating for months is different from one president acting on impulse. Collective action constrains adventurism. It forces leaders to justify their plans to sceptical allies. It builds legitimacy and shares burdens. The authority comes not from a UN resolution but from the consent of free states acting together. This is not a loophole. It is what enlightened self-interest looks like in practice – the discipline of persuading others before acting, rather than acting alone and daring others to object. The same logic applies domestically: a president who bypasses Congress on war is doing abroad what those who believe in limited government would never tolerate at home – concentrating power in the executive and escaping the discipline of deliberation.

Right intention asks whether the intervener’s motives are genuinely humanitarian. That matters, but motives are hard to verify. The real work is done by the other criteria – particularly just cause and manifest loss of legitimacy. If those are met, mixed motives are tolerable. If they are not, pure motives cannot save the intervention. What matters for the order is not purity of heart but whether the intervention strengthens or weakens the system of constraints.

Last resort and proportional means remain sound and need no revision.

Reasonable prospects of success should be strengthened into a requirement for a credible plan for what follows. International administration, supervised transition, regional integration as a goal. Regime change as part of a political settlement, not regime change as spectacle. The hardest part of any intervention is not the military operation but the aftermath. Without a plan, you create a vacuum that is often filled by forces worse than what you removed – and a failed intervention damages the order more than no intervention at all. R2P gestures at this with ‘reasonable prospects,’ but the historical record – Libya, Iraq, Afghanistan – suggests the criterion needs teeth.

To these I would add a sixth criterion not explicit in R2P: manifest loss of legitimacy. There should be strong evidence that the regime has lost the consent of its people – stolen elections, mass population flight, systematic repression. This matters because it shapes the prospects for a stable aftermath and distinguishes intervention from conquest. A regime that retains genuine popular support, however distasteful its policies, is a poor candidate for intervention – and removing it would look to the world like exactly the kind of imperial overreach the order was designed to prevent. A regime that rules only by terror and fraud is a different case.

These criteria are an appeal to prudence – to the recognition that even justified ends can be undermined by unjustified means, and that means which undermine the order undermine the security of everyone who depends on it.

What About Everything Short of Force?

None of this implies that democracies are powerless short of military intervention. The tools available – targeted sanctions, Magnitsky laws, financial restrictions, support for secure communications, asylum for dissidents, diplomatic isolation, support for civil society – are not nothing. They are slow. But the comparison should not be with the satisfying speed of a raid. It should be with the decades of patient pressure that eventually brought down the Soviet bloc. That took forty years.

The rules-based order was never designed to topple dictators on demand. It was designed to prevent great-power war and to give smaller states space to develop without being devoured. Regime change was always the hardest case. The honest liberal position may be that some dictators fall only when internal conditions change – and that outside intervention often makes those conditions worse rather than better. Libya is the cautionary tale.

None of this is as satisfying as watching a dictator hauled off in handcuffs. But satisfaction is not the test.

Two Cases

How does the framework apply in practice? Consider two cases: Kosovo in 1999 and Venezuela in 2025.

NATO’s intervention in Kosovo lacked UN Security Council authorisation. Russia would have vetoed any resolution. Critics at the time called it illegal. But examine it against the criteria.

There was an ongoing atrocity. Slobodan Milošević’s forces were engaged in ethnic cleansing of Kosovar Albanians. Refugees were streaming across borders. Mass graves were being dug. The intervention aimed to stop killing that was happening.

There was multilateral consensus. Nineteen NATO democracies reached a consensus before acting. The decision was collective, not unilateral. Allies shared the burden and the risk.

The justification was principled. NATO explicitly invoked humanitarian grounds. The intervention was framed as protection of civilians, not acquisition of territory or resources.

There was a plan for what followed. Kosovo came under UN administration, then supervised independence, with European integration as the long-term goal. The aftermath was imperfect, but there was a theory of the case.

And the regime had manifestly lost legitimacy. Milošević’s brutality was documented and undeniable.

Kosovo met the criteria. Most in the West supported the intervention despite its lack of UN authorisation. And crucially, because it was multilateral and principled, it strengthened rather than weakened the norms that sustain the order.

Now consider Venezuela. One president acted alone, without congressional authorisation, without allied support, without international mandate. The humanitarian situation was dire – economic collapse, mass emigration, stolen elections – but it fell short of genocide or mass slaughter. By design, the bar here is high. Trump’s justification was openly transactional: oil, drugs, the Monroe Doctrine. There was no plan for what follows beyond Maduro’s removal. Maduro had certainly lost legitimacy – he stole an election, drove a quarter of his population into exile, and crushed all opposition. But that is one criterion out of five. The operation fails on the other four. And because it was unilateral and transactional, it set a precedent that damages the order rather than defending it.

The contrast is not an embarrassing inconsistency. It is the framework working as intended.

Why Constraints Matter

The realist will object: constraints are for the weak. If America has the power to remove a dictator, why not use it? Who cares about frameworks and criteria when the result is one fewer tyrant?

The answer comes from enlightened self-interest itself.

First, the symmetry problem which I explored in that earlier essay. If America claims a sphere of influence in the Western Hemisphere, where it decides which governments are acceptable and removes those that are not, it validates identical claims by other great powers. A precedent of seizing oil and toppling a neighbour in the name of a nineteenth-century doctrine will not be read as an exception; it will be read as a model. Russia gets Eastern Europe. China gets the South China Sea and Taiwan. The rules-based order was built precisely to prevent this – to create a system in which even powerful states are bound by constraints, and smaller states have room to breathe. Dismantling that order does not serve American interests. It serves the interests of those who want a world without rules – and America will not always be the strongest player in such a world.

More fundamentally, those who believe in limited government should understand better than anyone that unconstrained power is dangerous. That is the entire case for constitutionalism, for separation of powers, for the rule of law. The point is not to trust concentrated power even when it is wielded by allies, because power corrupts and precedents outlast the individuals who set them.

The constraints that liberals built after 1945 – the UN Charter, the prohibition on aggressive war, the architecture of alliances and treaties – were not sentimental gestures. They were hard-won lessons from two world wars. They reflected the recognition that a world in which great powers do whatever they can get away with is a world that tends toward catastrophe. They were, in other words, the ultimate expression of enlightened self-interest – the recognition that binding yourself to rules serves you better than reserving the right to break them.

Trump is now dismantling those constraints. His defenders say the old order was hypocritical, inconsistently applied, often ignored. They are right. But the answer to imperfect rules is not no rules at all. The answer is to improve the rules while maintaining the principle that rules matter.

The framework also matters because Venezuela will not be the last case. The question will not be whether regimes are loathsome, but whether the conditions for justified intervention are genuinely met.

Maduro deserved his fate. But ‘he deserved it’ is not a framework. This essay has tried to offer one – grounded in the idea that maintaining the order is itself the interest, that constraints protect the order, and that criteria for intervention are how we distinguish defence of the order from its destruction.