If we review the teachings and comments on war from the popes of the last century, most especially from the end of World War II up to the present, we find a strong and constant refrain of “no” to war. There is a striking consistency in this realm of papal teaching, emphasizing again and again that war is not God’s will and is always a sign of human failure.
It is not surprising that the tenures of the popes from Pope John XXIII to Leo XIV correspond to substantial changes in modern warfare. In light of the devastation modern weapons can cause, especially for the innocent and noncombatants, these pontiffs have stressed that war must always be a truly last resort. However, as we look at the outbreak of wars in recent decades, one is left to wonder if Catholics are listening to the popes on a topic of the gravest urgency.
John XXIII and Paul VI
We can begin a brief review of papal teaching with Pope John XXIII. At a time when the world was engaged in an ever-increasing arms race and buildup of nuclear weapons, and after the potential use of such weapons became very real during the Cuban missile crisis, Pope John XXIII issued his encyclical “Pacem in Terris” (1963) calling for mutual disarmament of such weapons, quoting his predecessor, Pope Pius XII: “Nothing is lost by peace; everything may be lost by war.”
Then, in 1965, Pope Paul VI became the first pope to address the United Nations, where he affirmed their core mission and forcefully pleaded: “Never again war, never again war! It is peace, peace, that has to guide the destiny of the nations of all mankind!” Shortly thereafter, the bishops of the world, united with Pope Paul VI at the Second Vatican Council, promulgated the Pastoral Constitution “Gaudium et Spes,” where they teach: “Peace is not merely the absence of war. Nor can it be reduced solely to the maintenance of a balance of power between enemies. Nor is it brought about by dictatorship. Instead, it is rightly and appropriately called ‘an enterprise of justice’ (Is. 32:7).”
Pope Paul VI would come back to this teaching many times, and in his 1972 address for the worldwide Day of Peace he coined a phrase that continues to guide the work of many Catholic-sponsored groups advocating for peace to this day: “We repeat this today in a more incisive and dynamic formula: ‘If you want Peace, work for Justice.’” But he also spoke out against specific conflicts and was an early advocate for an end to the war in Vietnam. On the first anniversary of his memorable speech before the United Nations (this time before a crowd of over 150,000 gathered in Rome), Pope Paul VI asked all people, but especially his fellow Catholics, to join him in prayer for an end to the Vietnam conflict, calling for ceasefires and negotiations.
He later wrote President Lyndon Johnson directly, and even when his pleas were not heeded, he never stopped advocating for an end to that war, pointing to the horrendous losses of life and the devastation taking place in Vietnam.
John Paul, Benedict and Francis
Pope John Paul II, Pope Benedict XVI and Pope Francis continued this tradition of prophetic papal teaching on war. On hundreds of occasions in speeches, audiences, homilies or their weekly Angelus addresses, these popes called us to end war and violent conflicts wherever they were taking place across the globe. Even when they recognized the right of nations to defend themselves and protect innocent lives when attacked (for example, the people of Ukraine in the face of the Russian invasion), the responses of these popes have always highlighted the excesses inevitably created by the use of modern weapons.
For example, in 1991, Pope John Paul II recognized that Saddam Hussein’s invasion of Kuwait and the annexation of its oil fields was unjust. The pope initially used diplomatic channels to convey his concerns. But when the buildup to a full-blown war between Iraq and a coalition of forces including the United States and its allies began in 1991, Pope John Paul II spoke out publicly, pointing out the inevitable harm such a war would cause and pleading for the use of means other than war to counteract Hussein’s aggression.
When terrorists attacked the United States on Sept. 11, 2001, Pope John Paul II immediately condemned the attacks and expressed profound sorrow for the loss of life in the United States. But as America’s response to these attacks caused grave humanitarian crises in Afghanistan and Pakistan, the pope called for an end to the destructive tactics employed. In 2003, and motivated by the assertion (later entirely disproved) that Saddam Hussein and Iraq were in possession of weapons of mass destruction with their use deemed imminent, Pope John Paul II quietly used his personal representative, Cardinal Pio Laghi, a friend of the Bush family, to try to persuade the president not to go to war, stressing that such a war would be illegal and unjust.
At the same time, and in the public forum in his Jan. 13, 2003 address to the diplomatic corps, Pope John Paul II forcefully declared: “No to war! War is not always inevitable. It is always a defeat for humanity. International law, honest dialogue, solidarity between States, the noble exercise of diplomacy: these are methods worthy of individuals and nations in resolving their differences.”
In more recent years, Pope Francis’ interventions in response to the Russian invasion of Ukraine, as well as in regard to the actions of Israel in Gaza, exhibit that same reluctance of popes to support any war due to the disproportionate harm they inevitably cause. In a Sept. 15, 2022, interview with reporters on a flight to Rome from Kazakhstan, Pope Francis affirmed the right of Ukraine to defend itself: “To defend oneself is not only licit, it is also an expression of love toward one’s homeland.”
He even cautiously opened the door for other nations to supply arms to Ukraine, but only if done with the right intention—to help Ukraine defend itself but not as a means to expand the war or create additional casualties.
He likewise referenced the need to dialogue with the opposing party: “I don’t exclude dialogue with any power that is at war, even if it is with the aggressor. It may smell, but one has to do it.” It is worth noting too that on the prior day, in the talk he gave in Kazakhstan at the 7th Congress of Leaders of World and Traditional Religions, Francis reiterated: “God is peace. He guides us always in the way of peace, never that of war.”
He likewise had particularly critical words to direct to religious leaders who try to use religion to justify war, a criticism he made about Patriarch Kirill of the Russian Orthodox Church a few months earlier, warning him not to turn himself into “Putin’s altar boy.”
Similarly, when Hamas terrorists invaded Israel and massacred 1,200 civilians and took 240 hostage in 2023, Pope Francis expressed his horror and sorrow at what took place and acknowledged a nation’s right to self-defense. But the pope then went on to remind us that even then, war is always a tragedy: “[M]ay it be understood that terrorism and war do not lead to any resolutions, but only to the death and suffering of many innocent people. War is a defeat! Every war is a defeat.” And three days later (Oct. 11, 2023) he said:
One who is attacked has the right of self-defense, but I am very concerned about the total siege under which Palestinians are living in Gaza, where there also have been many innocent victims…Terrorism and extremism will not help reach a solution to the conflict between Israelis and Palestinians, but only increase hatred, violence and vengeance and only make each other suffer.
Ignored by Catholics
Time and again, as popes have offered those prophetic words,“never again war,” not only do those in power ignore them, but the vast majority of Catholics seem oblivious to them as well. I am left to wonder if national identity leads many to put country before God, and to see papal teaching as pious sentiment rather than an authentic expression of the Gospel of Jesus Christ for the world today. The need to exert power, to prove our side is right, to demonize the enemy in order to justify the damage and carnage war creates, seem to capture the minds and hearts of people far more than a thirst for peace, a commitment to work for justice or a willingness to consider the wisdom of the successors of St. Peter.
I am left to ponder with some anxiety whether it will be the same today for us as Catholics and citizens of the United States. How will we respond as our government makes extra-judicial decisions to destroy ships in international waters, killing those on board with no justification beyond labeling the dead “narco-terrorists”? Or when, contrary to international law, it kidnaps a head of state to create regime change while at the same time sidelining the leader-in-exile for whom the people democratically voted?
Will we listen to the Holy Father and his discernment in the face of our nation’s unilateral threat to take over Greenland without any legal authorization, or cause as much economic suffering as possible for the innocent people of Cuba in an effort to force the ousting of its leader? And while it is all but impossible to mourn the assassination of those recently killed leaders in Iran who themselves were responsible for the suffering and deaths of untold thousands, have we not once again caused tremendous destruction and suffering for the innocent people of Iran—with no clear motivation for our attack, and the vague allegation of Iran being on the verge of attacking the United States having once again been disproven?
Have we once again created a situation of war resulting in an escalation of violence and suffering, and with many innocent people being harmed, including the deaths of children and teachers?
It is significant to note a more recent justification for war, referred to as “preventive” or “preventative war.” The idea that one could justify the use of war or violence by arguing that it was preventing something even worse actually began with the 2003 Gulf War. It is employed again today by some of those who advocate for a war with Iran to justify our nation’s actions. A number of American supporters of this concept even tried to convince the Vatican that it was a legitimate extension of the just war tradition. Their basic argument is that unless we act now, something far more devastating will occur later. But the Vatican soundly rejected such an attempt to justify the use of force and continues to reject it as a justification for armed intervention into Iran.
The just war tradition developed as a way to limit the use of violence between nations, not as a way to justify pre-emptive violence. For example, Cardinal Ratzinger, the future Pope Benedict XVI, as head of what was called at the time the Congregation of the Doctrine of the Faith, simply dismissed the idea altogether at the time of the 2003 Gulf War, saying: “The concept of preventive war does not appear in the catechism.”
Earlier this year, the current Vatican Secretary of State, Cardinal Parolin, stated:
If states were to be recognized as having a right to ‘preventive war,’ according to their own criteria and without a supranational legal framework, the whole world would risk being set ablaze. This erosion of international law is truly worrying: justice has given way to force; the force of law has been replaced by the law of force, with the conviction that peace can arise only after the enemy has been annihilated.
Equally concerning are those voices that have tried to characterize the aggressive actions of the United States military as “holy,” likening military personnel to “holy warriors.” Some even have invoked the language of a “holy crusade,” as though this is a conflict rooted in religion. Our current “Secretary of War” (an alarming new name for what was formerly the “Department of Defense” as it implies that defense is no longer the primary purpose of armed conflict!) is the most outspoken in the use of such language.
Language that tries to baptize the use of weapons of war with a religious, even Christian veneer—as though God is on our side, and Jesus will see us to victory—is always to be rejected as a lie if not blasphemous. Our history of the Crusades should have taught us long ago that tying war to religion is never a good thing as it distorts the evil of war and too easily blinds us to the harm, contradictions and absurdities of war.
Disciples or patriots?
In considering the ramifications of our failure to listen to papal teaching, American Catholics should also seriously consider what these wars, conflicts, and acts of violence have cost us as a nation. For example, the current administration, in an alleged effort to reduce what they deemed wasteful federal spending, terminated a number of departments and employees of various U.S. agencies, one of which was the U.S. Agency for International Development. This agency managed a highly praised and seemingly successful foreign aid program with a budget of approximately $25 to $35 billion per year. While this is admittedly a large amount of money, USAID’s education, health, environmental, food and water initiatives contributed to a significant reduction in age-related mortality, especially children. (See this July 19, 2025, study published in The Lancet).
Meanwhile, it is now reported that the White House anticipates requesting up to $200 billion from Congress for the ongoing war with Iran—additional funding over and above the regular Pentagon budget. The funding of USAID was saving lives, even as it was enabling a sense of solidarity and good will among the people of the world and the United States as a nation. It was an example of how and why we can be justly proud of the United States. However, the funding for war requires significantly more money and results not in saving lives but in destroying them in a conflict that many conclude did not need to occur at all. Will not this funding, along with the violence and destruction it will empower, create a threat of even more global conflict?
We Americans can be proud of the many ways our great nation has been a beacon of hope, freedom, the rule of law and humanitarian aid for the world in times of need. But we cannot be proud of the harm we inflict on other nations, most especially when it is not morally justified. We cannot call ourselves both disciples and patriots if we support, without any protest or criticism, the actions of our government leaders when they contradict the moral law. Rather, as citizens we need to call our leaders to uphold the values of our American republic in all that they do, while as disciples, our faith dictates that we take a stand for peace, unity and truth.
I urge Catholics in the United States, along with people of good will everywhere, to listen more intently to the words and wisdom of our popes. Pope Leo XIV has been speaking forcefully about the destruction caused by the aerial bombings in Iraq and Lebanon, begging that such inhumanity stop and dialogue toward peace open up: “We cannot remain silent in the face of the suffering of so many defenseless people who are victims of these conflicts. What hurts them hurts all of humanity. The death and pain caused by these wars is a scandal for the entire human family and a cry that rises to God!” (Angelus Address, March 22, 2026).
Certainly, for us as Catholics, we need to allow such papal teaching to shape a true and moral patriotism that is not afraid to question the decisions of leaders when, for all intents and purposes, such decisions appear unjustified and immoral. Let us not be complicit with the evil that war unleashes, especially when the use of violence clearly is not a last resort. Rather, let us be witnesses to peace and nonviolent means of resolving conflict. It is precisely our faith, bolstered again and again by the wisdom of the popes, that can give us the courage to name the evil that war causes and to be in solidarity with peacemakers and war’s victims.
To accomplish this critical work of the Gospel, it seems to me that the popes have been fulfilling their mission in prophetic ways. Now is the time for the faithful to fulfill our own mission, which begins simply by listening—listening deeply and seriously to the consistent teaching of our popes and allowing that message, rooted firmly in the Gospel, to form us as greater disciples.
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