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Under Pope Leo XIV, What’s Next for the Catholic Church’s Nuclear Weapons Platform?

Vatican City - Ploughshares
Rebecka Green
May 29, 2025

Two weeks ago, newly appointed Pope Leo XIV engaged in a first-week tradition well known to leaders across the world: an introductory flurry of posts on X. “Peace” was the theme of his seven starter posts, which appeared on feeds across the globe on May 14.  

Leo XIV drew attention to the Christian diaspora, the importance of dialogue across nations, and lamented the lives lost to violence and “military conquest.” To cap off the day’s social media blitz, the official X account of the papal office addressed war and weapons: 

“War is never inevitable. Weapons can and must fall silent, for they never solve problems but only intensify them. Those who sow peace will endure throughout history, not those who reap victims. Others are not enemies to hate but human beings with whom to speak.” 

The condemnation of weapons and violence in favor of peacebuilding resonated with the global public. Leo XIV’s statement is currently the third most “liked” in the short history of the Pontifex’s newest X iteration. Having faith and world leaders speak in favor of a world free from the threat of nuclear weapons is a vital show of solidarity for a nuclear weapons-free future and Ploughshares’ mission.  

How has the papal office historically approached nuclear weapons policy?

The Catholic Church—and many other faith communities—have been instrumental in nuclear diplomacy for decades. There have been eight popes since the nuclear weapons were first developed and deployed in 1945, including the newly instated Leo XIV and Pope John Paul I, who held office for only 33 days. 

  • Pope Pius XII held the papal office as the world was realizing the power and irreversible consequences of nuclear weapons. He stated in 1948 that nuclear weapons are “the most terrible weapon that the human mind has ever conceived” and kept a close eye on scientific development throughout the 1930s and 40s, specifically atomic research. 
  • Pope John XXIII’s 1963 encyclical, Pacem In Terris, is the only encyclical explicitly addressing nuclear weapons, and contains a dedicated section on arms control and nuclear disarmament: “Nuclear weapons must be banned. A general agreement must be reached on a suitable disarmament program, with an effective system of mutual control.” (Pacem In Terris 59). 
  • In the months following the signing of the Treaty on the Non-Proliferation of Nuclear Weapons in 1968, Pope Paul VI spoke to the urgency of the moment and “putting an end to the nuclear arms race,” explicitly naming disarmament as the goal. 
  • In 1981, with Cold War tensions coming to a boil, Pope John Paul II addressed the United Nations University in Hiroshima: “Our future on this planet, exposed as it is to nuclear annihilation, depends upon one single factor: humanity must make a moral about-face.” He acknowledged the moral acceptability of deterrence, but as a means towards ultimate disarmament. During this time, the Pontifical Academy of Sciences in Vatican City served as a middle ground forum for scientists to discuss nuclear science and policy. 
  • Pope Benedict XVI, during his General Audience in 2010, said: “Progress toward a collaborative and secure nuclear disarmament is closely connected with the full and rapid fulfillment of the relevant international commitments.” He went beyond merely questioning nuclear deterrence and called into question its moral legitimacy. 
  • Pope Francis expressed the strongest condemnation of nuclear weapons in the papacy’s history. During his landmark visit to Japan in 2019, he said: “The use of atomic energy for purposes of war is immoral, just as the possessing of nuclear weapons is immoral … How can we speak of peace even as we build terrifying new weapons of war?” He is remembered for emphasizing that the mere possession of nuclear weapons is immoral—not just their use. 

Does Pope Leo XIV have a public position on nuclear weapons? 

Only time will tell if Leo XIV will follow in his predecessors’ footsteps, particularly those of Pope Francis, and call outright for nuclear disarmament and reject nuclear deterrence. Aside from May 14’s X post condemning weapons more broadly, his office has yet to make a statement specifically addressing nuclear weapons. 

Nearly two decades ago, he visited Nagasaki to meet with clergy and visit churches; John Paul II and Francis are otherwise the only popes who made visits to Hiroshima and Nagasaki. Leaders of Hibakusha groups—referring to survivors of the atomic bombings of Hiroshima and Nagasaki—have called for Pope Leo to “think about peace first and aim for a world without nuclear weapons” and note the significance of having a new pope who comes from the United States—a major nuclear power. 

What is the likelihood of Pope Leo XIV supporting nuclear disarmament? 

Precedence, history, and geopolitical indicators—such as rising tensions in nuclear flashpoints and ongoing diplomatic efforts between the US and Iran—all support Leo XIV and the Catholic Church continuing its tradition of condemning nuclear weapons. Beyond just nuclear disarmament policy, the Catholic Church emphasizes the “integral” nature of all creation, with Pope Francis once citing Pope John XXIII’s promotion of “integral disarmament.” According to Ploughshares grantee, the Arms Control Association, this “assumes that the long-term goal of abolishing nuclear weapons has to be part of a much larger cosmopolitan project of developing a global ethic of peace and solidarity that can ground a system of cooperative security.” 

Integral disarmament connects deeply with Ploughshares’ emphasis on the interconnected nature of nuclear weapons with the other core concerns facing global society. Ploughshares President Dr. Emma Belcher spoke to this on our Story Center, citing the importance of “working to integrate nuclear policy into comprehensive security frameworks that address climate change, democratic erosion, sustainable development, and other interconnected challenges.” 

Continuing to grow and connect the broader nuclear disarmament field is a key part of addressing these interconnected challenges. And while a few social media posts from the pope aren’t necessarily anything to write home about in the policy realm, Ploughshares recognizes the importance of connecting with global audiences wherever they are: online, on the ground, in houses of worship, and beyond.

Our grantee, the Arms Control Association, has written expansively on this topic over the year with a closer look at the Holy See/Catholic Church as a whole. Additional reading and sources:

Author

  • Rebecka is the Communications Manager at Ploughshares, where she serves as editor of the organization’s Story Center, manages core digital platforms, and assists with communications strategy across departments. Prior to coming to Ploughshares, Rebecka worked in communications at a D.C.-based think tank focused on religion in the United States, at a philanthropic resource network, and in higher education. She holds a B.A. in English and religious studies and has a background in the arts, focused on creative writing and digital production. She is based in Washington, D.C. by way of small-town Iowa.

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