Pope Leo pushes review of just war doctrine amid tensions with Trump

Pope Leo XIV is set to convene the world's cardinals behind closed doors on June 26 to discuss whether the Catholic Church should revise its centuries-old doctrine of "just war," a move that could further strain relations with the administration of U.S. President Donald Trump.

The meeting follows recent tensions between the Vatican and Washington over the conflict involving Iran. After Leo said followers of Christ were never on the side of those who "once wielded the sword and today drop bombs," U.S. Vice President JD Vance said the pontiff should be "careful" about challenging the Church's long-established teaching on just war, Politico reports.

In an encyclical issued last month, Leo argued that the doctrine, "which has all too often been used to justify any kind of war, is now outdated." He later told journalists: "The notion of a just war no longer applies … [The theory] was developed in centuries when no one could have imagined the weapons we have today or humanity's capacity for destruction."

Senior clergy expect the meeting to consider stricter criteria for when military force can be justified in self-defence and to place greater emphasis on exhausting diplomatic options before armed conflict.

Archbishop Timothy Broglio, head of the U.S. Archdiocese for the Military Services, said modern warfare required a reassessment of the doctrine.

"Because of the cataclysmic encounters that we've had and also the potential danger that's there, I think the pope wants to take advantage of bringing to bear all of the modern considerations that now have, in a very real way, altered the nature of warfare," Broglio said.

He added that the doctrine could evolve to distinguish more clearly between defensive wars and preventive military action.

"I would see the situation in a place like Ukraine that was attacked as being much different from the preventative approach to some place like Iran," he said.

Monsignor Vincenzo Paglia, president emeritus of the Pontifical Academy for Life, said Leo was "stepping on the gas" of a process begun by previous popes, describing it as "Leo's first big move."

"I believe the popes are advancing the theological doctrine of peace," Paglia said. "The Church isn't a museum. It's a living body."

Broglio said the meeting's immediate outcome was likely to be "an appeal to negotiate before, not after, a conflict."

By Sabina Mammadli