Pope Leo XIV’s call for nuclear disarmament is part of a broader vision of peace: nuclear weapons are not merely a strategic or political issue but a grave moral question involving human dignity, international responsibility, and the future of humanity.

The development of his position

Leo XIV has returned to the subject in several contexts:

• In his first Urbi et Orbi blessing, he described Christ’s peace as “unarmed and disarming, humble and persevering”, linking peace to dialogue, bridge-building, and solidarity among peoples. 1
• In his address to diplomats in May 2025, he explicitly called for an end to the production of “instruments of destruction and death,” insisting that national defense must not become a race to rearm. 2
• In January 2026, he addressed the countries possessing nuclear arsenals and called for renewed efforts connected with the New START Treaty, warning against a new arms race involving increasingly sophisticated weapons and artificial intelligence. 3
• His 2026 encyclical Magnifica Humanitas provides the most developed analysis, criticizing nuclear modernization, the normalization of “tactical” nuclear weapons, and the assumption that nuclear deterrence is indispensable for security. 4

These interventions show a consistent trajectory: Leo XIV is not making an isolated appeal but integrating nuclear disarmament into a wider Catholic account of peace and technological responsibility.

His central criticism: deterrence has become an ideology

The pope’s principal target is not simply the existence of weapons but the belief that nuclear deterrence is necessarily the foundation of peace. He describes this belief as “widespread yet erroneous.” 4

Deterrence is the strategy by which a state seeks to prevent attack by threatening retaliation. Leo XIV’s concern is that this strategy can become self-justifying: weapons are retained because they are said to guarantee security, while the perceived need for security then becomes the reason to develop more weapons.

According to Magnifica Humanitas, this logic has contributed to:

• a renewed arms race;
• the weakening or dismantling of nuclear-reduction agreements;
• the development of smaller or “miniaturized” weapons;
• the idea that nuclear weapons could be used in a limited or “tactical” way. 4

The danger, in his analysis, is psychological as well as military. When weapons are described as more precise, smaller, or usable in restricted circumstances, the moral and political threshold for employing them may be lowered. The pope therefore rejects the assumption that technological sophistication makes nuclear war morally or practically manageable.

Why “tactical” nuclear weapons are especially troubling

The term tactical nuclear weapon generally refers to a nuclear weapon intended for use against military targets in a more limited theater of war, rather than in a large-scale strategic attack. Leo XIV warns that the very concept can make nuclear use appear less improbable. 4

This concern reflects a deeper moral problem. Nuclear weapons possess destructive capacities that do not remain confined neatly to military targets. Their effects can include mass civilian death, long-term radiation, environmental devastation, displacement, and consequences extending across national borders and generations.

The pope’s argument is therefore directed against attempts to separate nuclear weapons into supposedly acceptable and unacceptable categories merely by scale. A smaller nuclear weapon may still initiate uncontrollable escalation or cause massive harm to noncombatants. Magnifica Humanitas stresses that the development of such weapons makes their use appear “more viable,” which is itself a sign of moral and political danger. 4

Disarmament as a service to human dignity

Leo XIV frames disarmament positively. It is not simply a technical reduction of military stockpiles or a concession made under diplomatic pressure. He calls nuclear disarmament “a service to peace and the dignity of the human family.” 5

This language places the issue within Catholic social teaching’s understanding of the common good. The common good is not merely the security of one state or alliance; it includes the conditions that allow all people and communities to live with dignity. Weapons capable of destroying humanity threaten that common good at its most fundamental level.

The pope’s approach also implies that security cannot be defined exclusively in military terms. Genuine security includes:

• respect for human life;
• stable international relationships;
• reliable diplomatic institutions;
• justice among nations;
• protection of future generations;
• responsible control over dangerous technologies.

For Leo XIV, peace is not simply the absence of open conflict. In his presentation of Magnifica Humanitas, he states that “peace, not merely the absence of war, is justice at work.” 5

The Treaty on the Prohibition of Nuclear Weapons

Leo XIV recognizes the Treaty on the Prohibition of Nuclear Weapons as an important development. He notes that it entered into force in 2021 and had the support of more than seventy countries. At the same time, he observes that its practical impact risks remaining limited because the major nuclear powers have not accepted it. 4

This is a significant feature of his position. He neither dismisses the treaty as unrealistic nor presents it as sufficient by itself. His assessment contains both moral affirmation and political realism:

• Moral affirmation: the treaty expresses a serious judgment that nuclear weapons are incompatible with the protection of humanity and the pursuit of peace.
• Political realism: an agreement lacking participation by the major nuclear powers cannot by itself eliminate the existing nuclear order.

The implication is that disarmament requires both principled condemnation and sustained diplomacy. Symbolic commitments matter because they shape international norms, but they must eventually be accompanied by verifiable, reciprocal, and effective reductions.

A challenge to the “security through accumulation” model

Leo XIV’s diplomatic addresses repeatedly contrast two models of peace.

The first is peace through force and deterrence. He associates this with the belief that military superiority or the threat of retaliation is the primary safeguard against war. In January 2026, he warned that this conviction remains persistent and insisted that peace requires continuous and patient efforts of construction, not merely military readiness. 3

The second is peace through dialogue, law, cooperation, and justice. In his 2025 address, he called for renewed multilateral diplomacy and international institutions designed to resolve disputes within the international community. 2

This does not mean that Leo XIV denies the responsibilities of governments to protect their citizens. His concern is that defense can be detached from moral limits and transformed into permanent rearmament. His formulation is careful: the requirement that peoples provide for their defense must not become a race to rearm. 2

Thus, his call for disarmament is not equivalent to advocating political passivity or unilateral vulnerability. It is a call to replace indefinite dependence on nuclear arsenals with cooperative structures capable of addressing the causes of conflict.

The connection with artificial intelligence

A distinctive element of Leo XIV’s argument is the connection between nuclear weapons and artificial intelligence. He warns that a new arms race may involve weapons made increasingly sophisticated through AI. 3

In Magnifica Humanitas, he argues that nuclear disarmament belongs to a broader moral framework: every great technical power must be accompanied by moral discernment and public control. 5

He applies the same principle to AI, arguing that it must be “disarmed”—not rejected, but freed from systems of domination, exclusion, and death. 5

The connection is important for three reasons:

1. Human control: decisions involving life and death cannot be surrendered to systems that lack conscience and moral responsibility.
2. Escalation: AI may accelerate weapons development and reduce the time available for human judgment during a crisis.
3. Concentration of power: technological dominance can deepen geopolitical inequalities and make military power less accountable.

Leo XIV’s wider principle is that technical capability does not automatically confer moral legitimacy or the right to govern. In his discussion of AI, he argues that technical power must not be confused with the right to rule humanity. 6

The theological foundation

The pope’s argument is ultimately Christological and anthropological: peace begins with the peace of the risen Christ and is directed toward the dignity of every human person. His first blessing presented peace as a divine gift that nevertheless demands human cooperation through dialogue, encounter, and solidarity. 1

His diplomatic teaching adds that peace requires conversion of the heart. Pride, vindictiveness, aggressive speech, and the desire for conquest can generate the same destructive mentality that later appears in military systems. 2

This is why his position cannot be reduced to arms-control policy. Nuclear disarmament is connected to:

• the rejection of domination;
• the defense of innocent life;
• forgiveness and reconciliation;
• the conversion of political ambition;
• the construction of justice among peoples.

His message to religious leaders describes peace as “unarmed and disarming, humble and persevering,” and calls religious communities to speak together wherever human dignity is threatened. 7

What the call demands in practice

Taken together, Leo XIV’s statements point toward several practical priorities:

• renewed nuclear-reduction agreements;
• preservation and strengthening of arms-control treaties;
• serious engagement by states possessing nuclear arsenals;
• rejection of the normalization of “limited” nuclear war;
• stronger multilateral diplomacy;
• public and ethical oversight of military technologies;
• international cooperation rather than unilateral arms competition. 3

His appeal is therefore directed first to governments, especially nuclear-armed states, but it also has implications for citizens and Catholic communities. The pope’s 2025 address identifies dialogue, religious cooperation, truth, justice, and concern for vulnerable persons as conditions for peace. 2

Overall assessment

Pope Leo XIV’s call for nuclear disarmament is morally uncompromising but politically gradualist. He condemns the illusion that ever more sophisticated nuclear arsenals provide a lasting foundation for security, yet he recognizes that treaties and disarmament initiatives must involve the states that possess those weapons. 4

His central claim is that nuclear deterrence cannot be treated as an unquestionable principle. Security must be pursued through disarmament, diplomacy, justice, international law, and the conversion of the attitudes that produce conflict. Nuclear disarmament is not presented as naïve idealism but as a necessary service to humanity in an age when both nuclear weapons and artificial intelligence can magnify the consequences of human error, fear, and political rivalry.

In summary, Leo XIV is calling the international community to move from security based on the threat of mutual destruction toward peace built through responsible cooperation, moral restraint, and the protection of the human family.