VATICAN CITY (RNS) — Pope Leo XIV will host his second major summit of cardinals Friday and Saturday (June 26-27) at the Vatican, where they are expected to address questions of war, peace and whether Catholic teaching can still rely on the centuries-old theory of a “just war” in an age of drones, nuclear weapons and artificial intelligence.

The summit, called an extraordinary consistory, invites the 241 members of the College of Cardinals to Rome with the goal of assisting and advising the pope on important church matters. An extraordinary consistory is considered among the pope’s most consequential consultations with cardinals, planned “when the special needs of the Church and more serious matters suggest it,” according to canon law.

The gathering underscores the pope’s intention to heed the cardinals’ request to be more active participants in leading the church after his election last year. Pope Benedict XVI never convened an extraordinary consistory, while Pope Francis only convened two, one in 2014 and the other in 2015. Leo has promised to hold such a gathering every year.

While Leo’s first consistory, in January, focused on missions and evangelization, the upcoming summit is meant to center on peace. With violent conflicts around the world, including in Europe and the Middle East, and as modern warfare becomes increasingly more efficient and lethal, Leo and the cardinals are to reconsider whether any war can be morally legitimized under church teaching.

The dean of the College of Cardinals, Cardinal Giovanni Battista Re, said the summit will address how the church can overcome that just war theory is “too often invoked to justify any war,” in a letter outlining the anticipated discussions.

Just war theory in Catholic teaching refers to a set of moral brakes where wars are narrowly justified, primarily when they are for defensive purposes. 

Pope Leo XIV talks to journalists as he leaves his residence in Castel Gandolfo, on the outskirts of Rome, May 5, 2026. (AP Photo/Gregorio Borgia)

Pope Leo recently questioned just war theory, especially as it concerns the ongoing conflict between the U.S. and Iran, while answering questions from journalists aboard the papal plane for his weeklong visit to Spain earlier this month. “The problem is that the just war theory comes from centuries past when we couldn’t imagine the weapons, human beings’ ability for destruction,” Leo said.

According to the catechism of the Catholic Church, military force can only be justified to avoid “grave and certain” damage and when all peaceful alternatives have failed. It must also ensure that it will not unleash greater evil than the one it’s resisting.

The first session of the consistory on Friday morning will ask cardinals, “In what world are we to proclaim the gospel?” and is to focus on churches around the world. It’s not a coincidence that Polish Cardinal Grzegorz Ryś of Krakow will deliver the biblical meditation opening the discussion. Ryś ministers across the border from the conflict in Ukraine and has backed aid for Ukrainian civilians while condemning militarization in Europe. He has also said that war is born from idolatry of power and money and that peace cannot be imposed by force.

Most directly relevant to the consistory’s theme, Ryś said in a March interview that “preventive war is not a just war.” 

The consistory will enter the main focus of the discussions in its second session Friday afternoon and the third on Saturday morning, both centered on Leo’s first encyclical, “Magnifica Humanitas.” The encyclical, the pope’s first official document advising church teaching, was released in May and reflected on what it means to be human in an increasingly polarized society driven by war, inequality and technology, including artificial intelligence.

Pope Leo XIV, left, attends the presentation of his first encyclical, “Magnifica Humanitas: On Safeguarding the Human Person in the Time of Artificial Intelligence,” at the Vatican, May 25, 2026. (AP Photo/Alessandra Tarantino)

The head of the Vatican’s doctrinal department, Cardinal Victor Manuel Fernández, who presented the encyclical alongside Leo, will offer the introductory meditation for the second session, drawing on the title of the document’s fifth chapter, “The Culture of Power and the Civilization of Love.”

That chapter is centered on the themes of war and peace. Leo addresses normalization of war as a “paradigm shift,” in which the principles and international tools for peace are being eroded in favor of a culture of power. Meanwhile, new technologies and AI are making warfare not only more efficient but also more inhuman than ever, with machines increasingly taking over lethal decisions.

The church must resist this impetus by promoting a civilization of love, the document states, based on patient dialogue, diplomacy and renewed multilateral efforts.

In this chapter, Leo suggests that “without prejudice to the right to self-defense in the strictest sense, the ‘just war’ theory, which has all too often been used to justify any kind of war, is now outdated.”

After morning Mass presided by Re in St. Peter’s Basilica on Saturday, the cardinals will convene for the third session, on the theme “building in goodness.” Cardinal Stephen Brislin of Johannesburg will offer the meditation based on the introduction and conclusion of “Magnifica Humanitas.”

In this portion, cardinals will reflect on what the church can do to promote listening and reconciliation in dioceses and through their responsibilities. In the conclusion and introduction of the encyclical, Leo juxtaposes the biblical image of the Tower of Babel, founded on power and division, with the reconstruction of the city of Jerusalem as a grassroots endeavor.

Brislin will likely draw from his experience attempting to heal South Africa’s still-open wounds of racial discrimination and apartheid to outline a concrete path for the church built on truth, accountability and dialogue.

The final session of the consistory will shift the focus to implementing the Synod on Synodality, a massive consultation of Catholics created by Pope Francis in 2021 that resulted in two summits of bishops, or synods, at the Vatican. Cardinal Mario Grech, secretary-general of the Synod of Bishops, recently signed a document outlining a three-year implementation period for the synod, focusing on listening, inclusivity and mission.

Synodality will also be ingrained in the summit. After each meditation, participants will be divided into 20 groups to hold small discussions in which speeches will be limited to three minutes each.

After the final session, a moment will be dedicated to open dialogue between the cardinals and pope, who will deliver a broadcasted speech. The gathering will officially conclude on Monday, when Pope Leo will preside over a Mass at St. Peter’s Basilica for the Feast of Sts. Peter and Paul.