Auxiliary Bishop James Massa of Brooklyn, N.Y., addresses confirmation candidates during Mass May 5, 2022, at Holy Family Church in Queens, N.Y. (OSV News/Gregory A. Shemitz)
OSV News
Join the Conversation
Send your thoughts to Letters to the Editor. Learn more
On April 15, Auxiliary Bishop James Massa of Brooklyn, chair of the U.S. Conference of Catholic Bishops' Committee on Doctrine, issued a statement clarifying the Catholic Church's teaching on just war.
The statement came as President Donald Trump, Vice President JD Vance and other Trump administration officials have publicly challenged Pope Leo XIV's calls for peace amid the U.S.-Israel war on Iran and other conflicts.
"When Pope Leo XIV speaks as supreme pastor of the universal Church, he is not merely offering opinions on theology, he is preaching the Gospel and exercising his ministry as the Vicar of Christ," Massa said in the statement. "The consistent teaching of the Church is insistent that all people of good will must pray and work toward lasting peace while avoiding the evils and injustices that accompany all wars."
OSV News spoke at length with Massa regarding just war doctrine. This interview has been edited for length and clarity.
OSV News: Based on recent comments from Pope Leo XIV and various bishops, is it fair to say the Catholic Church's teaching on just war doctrine is at heart a call for peace?
Massa: Absolutely. Just war theory is always meant to make war, the legitimate use of force, a last resort defense of people.
When an aggressor has caused some grave, lasting, certain harm, and then when all other options have failed — peaceful options, negotiations, diplomacy, etc. — and when there's a real chance of success, those are the criteria. And that's called "jus ad velum," Latin for "just reasons for going to war."
And then the other big condition that's very important is that the fighting and the actual use of force will not cause worse evils than the harm you're trying to stop.
So clearly, going back to St. Augustine and his teacher St. Ambrose, and St. Thomas Aquinas, who brings it to another level — just war theory is never a blank check for violence.
What are some common misconceptions about the church's teaching on just war?
I think one is forgetting the use of violence, the use of war is always tragic. When anyone is the recipient of violence, it's always something terribly, terribly tragic — one more manifestation of original sin in a broken world.
So the church urges governments to exhaust every other possible means before going to war and before using force to achieve a noble end.
And I think the other thing that's sort of missed right now is, if you're going to go to war, you have to have a very clear endgame in mind. What is the purpose of it? What's the goal?
Arguably, in this current conflict, that has not been stated with consistency and clarity.
You're referring to the U.S.-Israel war on Iran?
Yes. The goal has been talked about in different ways. There is a repeated point made by the current administration that the goal is to have a denuclearized Iran.
But what else does it look like? Where do we end up in terms of relations among nations? And what's the path to peace in the region beyond this?
This all has to be stated clearly for there to be legitimacy in the use of force in such a high level of military engagement.
Chairs stand in a damaged building at Shahid Beheshti University in Tehran, Iran, April 4, 2026, amid the U.S.-Israeli war with Iran. (OSV News photo/Reuters/Majid Asgaripour, WANA)
Vice President JD Vance and others have cited World War II in defending the U.S.'s war on Iran. When people reference other wars in history in terms of just war theory, what are some things they need to keep in mind if they're trying to use the past as justification for the present?
One of the lessons of history — and clearly, this was the case with World War II — and especially in an age with weapons of mass destruction and with much more sophisticated technologies at play, is that we can't go it alone.
In World War II, the United States was part of a coalition, the Allied powers against the Axis powers, Germany, Italy and Japan. There was an endgame in view. The Allies were speaking about the United Nations, some international mechanism that would help to defuse conflict and prevent war from happening in the future. So, arguably there, the conditions of justified use of force were met.
But go back a little bit further, and I think we can put Pope Leo's comments of late against this backdrop: 110 years ago, we had a pope who was deeply, deeply troubled by the war that was raging at the time, namely World War I.
It was Pope Benedict XV, and he was pleading for a cessation of the war to bring the various parties to the peace table. He pleaded for that. He was speaking about the League of Nations before most of the leadership of the time, as the need for some international means of preventing such a catastrophic war from happening again. In World War I, we saw such massive slaughter — and that slaughter was committed by largely Christian nations, with baptized Catholics killing each other in battle. And it was deeply troubling.
So there you have kind of the first cry of the heart from a pope to speak to a global conflict. And I think that sets the stage for what other popes, from Pius X through St. John Paul II, Pope Francis, and up until Pope Leo XIV now, are pleading for: the use of international bodies to arrive at solutions to conflict rather than going to war.
What would you say to people who invoke papal support for the Crusades, and the Crusades themselves, as Christian justification for conflict? How does the church look at that now from the present moment?
Very simply, and in four words: We repent of them.
That message was folded into Pope St. John Paul II's apologies, the "mea culpas" that he gave 26 years ago (both in his bull for the Great Jubilee Year of 2020 and in his "Day of Pardon" homily on March 12 of that year) in which the pope, at the turn of the millennium, was looking back at the sins of the sons of daughters of the Catholic Church, and asking for forgiveness and repentance.
Was there any legitimacy to the efforts of the Crusaders? Some historians might want to argue that we were trying to free up access to the holy sites in the Holy Land when the various (Muslim) caliphates were the aggressor in various historical moments. Some may want to make that argument, but a war that is justified by means of the logic of a crusade betrays false reasoning.
You noted modern weapons of mass destruction, which pose risks now accelerated by artificial intelligence, as multiple experts have warned. Talk about the need for a clear understanding of Catholic teaching on just war in the light of AI.
We're removing human agency from decisions about how to conduct war and specific decisions that are made in the waging of war. So this applies to the criteria of "jus in bello" (the morality that governs combat, reflected both in Catholic teaching and in international humanitarian law).
Advertisement
So we have the criteria we use to determine whether it's legitimate to go to war, and then the criteria for the waging of war.
What are the conditions for justly waging war? First of all, there has to be noncombatant immunity. Wounded soldiers, innocent civilians and prisoners have to be respected, treated humanely.
One cannot indiscriminately destroy whole cities and their populations. The Second Vatican Council condemned that in Gaudium et Spes at paragraph 80. You have to avoid indiscriminate destruction.
And with the introduction of AI, this becomes more and more precarious.
What would you say to those who hold that Catholics can disagree as to whether the U.S.-Israel war on Iran is just or not?
The pope and the Magisterium of the church do not substitute for the conscience of individual Catholics. But for a Catholic to reason justly about the legitimacy of any war, he or she must be informed by the church's teaching and what the pastors of the church are currently saying.
As Cardinal Joseph Ratzinger, later Pope Benedict XVI, argued — and he was drawing on the thought of St. John Henry Newman — the pope is the guardian of conscience.
And that was basically saying to us, "Read Holy Scripture, look at what the church has been saying through the voice of her pastors about warfare in the modern era."
Yes, each of us must come to a decision, each of us must take a position based on conscience — but make sure that our consciences are well informed by the church's wisdom.
