Augustine’s Just War Theory Is Not The Alibi Some Think It Is

House Speaker Mike Johnson recently stated that Pope Leo's criticism of the Iran war was unfounded, and that Pope Leo should examine St. Augustine's Just War Theory. This is ridiculous on its face, since Pope Leo spent 12 years as the head of the Augustinian order, so would of course be well-versed on Just War theory.

But let's examine what the Just War theory is and how it applies today, because this is the deeper problem: Augustine is routinely invoked not as a moral constraint, but as a permission slip.

“St. Augustine of Hippo Receiving the Most Sacred Heart of Jesus,” by Phillipe de Champaigne, 1602-1674, French. (Wikimedia Commons)

St. Augustine did not write a tidy doctrine called “just war theory.” What he gave us instead was a set of moral guardrails rooted in a tragic realism about human nature. War, for Augustine, is always a sign of disorder. It may sometimes be necessary, but it is never clean, never righteous in the sense politicians like to imply, and never detached from the danger of moral corruption.

In Letter 189, Augustine insists that peace must always be the goal. In Contra Faustum, he names the real evils of war: not only killing, but the deeper sicknesses such as hatred, vengeance, cruelty, and the lust for domination. These are not side effects. They are the spiritual toxins that war reliably produces.

Over time, the Church distilled Augustine’s thinking into several criteria: just cause, legitimate authority, last resort, proportionality, and a reasonable chance of success. Crucially, these are not optional boxes to check. All must be satisfied.

So let’s apply them to the 2026 U.S.-Israel attacks on Iran.

Just Cause and Last Resort

The central question is not whether there were reasons. States always seem to have reasons. The question is whether there was a grave and certain threat that could not be addressed by any means short of war.

Public reporting indicates that negotiations with Iran were ongoing and, according to some mediators, even showing signs of progress. If that is true, the claim of “last resort” collapses. War cannot be justified simply because diplomacy is slow, frustrating, or politically inconvenient.

Augustine does not allow impatience to masquerade as necessity.

Right Intention

This is where the argument becomes even more strained. Among the stated goals of the campaign was regime change.

Augustine would have recognized this immediately as morally dangerous territory. War aimed at repelling aggression is one thing. War aimed at reshaping another nation’s political order is something else entirely. It edges into what he warned against most forcefully: domination driven by pride.

When the objective becomes control rather than defense, the moral center does not hold.

Proportionality

Even if one grants that Iran poses real strategic threats, the response must not unleash evils greater than those it seeks to prevent.

Civilian casualties in Iran have been significant. Infrastructure has been damaged. Regional instability has intensified. These are not incidental details; they are central to the moral evaluation.

Just war theory does not permit us to write off civilian deaths as unfortunate but acceptable. The burden is much higher than that. If the foreseeable human cost is immense, the justification must be overwhelming. That case has not been made.

Reasonable Hope of Success

Success, in Augustine’s sense, does not mean military dominance. It means a just and lasting peace.

Yet the conflict has not produced stability. Iran retains significant military capacity. The risk of escalation remains high. Maritime tensions threaten global consequences. The region is not closer to peace; it is further from it.

A war that multiplies conflict cannot be called successful simply because it is forceful.

The Deeper Augustinian Warning

There is a deeper issue here, one that Augustine would likely see more clearly than any policy analyst.

Even when a war meets all the criteria—and that is rare—it remains spiritually dangerous. It deforms those who wage it. It tempts nations into self-righteousness. It normalizes violence as a tool of problem-solving.

And this is precisely what we see in the rhetoric surrounding the Iran war: confidence bordering on certainty, moral clarity claimed too quickly, and criticism dismissed as naïveté.

Augustine would not recognize this as moral seriousness. He would recognize it as pride.

So Where Does That Leave Us?

Invoking Augustine against a pope who has spent years steeped in Augustinian thought is not just ironic. It reveals how casually the tradition is used.

Just war theory is not meant to justify wars after they begin. It is meant to restrain them before they start.

On the evidence available, the 2026 attacks on Iran struggle to meet multiple core criteria: last resort, right intention, proportionality, and the likelihood of a just peace. That does not make this a complicated moral gray area. It makes it a failure of the very framework being invoked to defend it.

Augustine is not a shield for power. He is a critic of it.

And if we are going to cite him, we should be prepared to let him speak.