Pope Leo's Warning About AI Weapons Reveals a Wider Divide With Donald Trump Over War and Global Diplomacy

Pope Leo XIV has issued an unprecedented theological rebuke against the militarisation of artificial intelligence, warning world leaders that delegating lethal decisions to autonomous battlefield algorithms is fundamentally immoral.

In his landmark first encyclical, Magnifica humanitas, published by the Holy See on 25 May 2026, Pope Leo called for advanced computing systems to be disarmed, declaring unequivocally that no mathematical calculation can make armed conflict ethically acceptable.

The encyclical says artificial intelligence needs to be 'disarmed' and states, 'No algorithm can make war morally acceptable.'

The papal decree deepens a profound geopolitical and philosophical divide with United States President Donald Trump, who has championed unconstrained technological supremacy against China whilst ridiculing existential artificial intelligence warnings as an elaborate hoax.

As Holy See envoys prepare to confront American and Russian delegations at a pivotal United Nations disarmament summit in Geneva, the pontiff's intervention establishes a defining moral challenge against the global escalation of autonomous robotic warfare.

A UN review conference is scheduled for 30 November to 4 December 2026, giving the Holy See another forum to press its disarmament case.

Pope Leo's AI Weapons Warning

Pope Leo's concern includes autonomous weapons that can select or attack targets. Pope Leo warns that entrusting algorithms to decide who is targeted risks obscuring responsibility. Those who design, authorise and use military technology, he argues, must remain accountable for its consequences.

The encyclical also questions the pressure to make military decisions faster. Speed can reduce time for human judgement, even when the consequences are irreversible.

Pope Leo says AI in warfare must be subject to strict ethical constraints and warns against a race to develop such weapons. Human beings, he argues, must retain meaningful control when lethal force is considered.

The Vatican's position also addresses who controls powerful technologies and who benefits from them. At the United Nations in September, Cardinal Pietro Parolin said, 'The control of these powerful tools must not remain in the hands of a select few; they must serve humanity, not the other way around.'

His address called for accountability in the use of lethal autonomous weapons and urged states to prioritise dialogue and the common good.

That appeal continues the Church's focus on disarmament. Pope Leo warns that new military technologies can reinforce the belief that security depends on ever-greater strength. His encyclical calls for negotiation and public oversight, linking AI weapons to the broader question of how governments limit the use of force.

AI Weapons and the Vatican's Divide With Trump

The contrast with Trump has become more visible during the war in Iran. Pope Leo criticised the conflict and said he would continue to speak out against war.

Trump responded by calling the pope 'terrible for Foreign Policy' in a social media post that also described him as 'WEAK on Crime'. The exchange followed Leo's public opposition to the US-Israeli war.

They have also differed over AI safety. In September, Pope Leo told reporters aboard the papal plane that experts' concerns about AI risks should be taken seriously and were not 'fake news'. Trump has called warnings about AI risks a 'hoax' and argued that the US must maintain its lead over China.

On arms control, the Vatican has urged international rules for lethal autonomous weapons, while the United States has not joined the Treaty on the Prohibition of Nuclear Weapons.

Pope Leo's warning is part of a wider argument about how governments define security. He has called for human responsibility and diplomacy to constrain military power, while Trump has emphasised US technological leadership and strength. The encyclical asks whether human judgement can keep pace with the systems governments are building.