Since the Iran war began in February, Pope Leo XIV has been a consistent thorn in Washington's side on the moral question of the conflict. On Saturday, June 6, aboard his papal flight from Rome to Madrid — his fourth foreign trip as pontiff — Leo made his most pointed statement yet.

"There is no just war there," Leo told journalists, according to reporting by NPR, Religion News Service, and Anadolu Agency. The remarks came in direct response to a question by Italian journalist Franca Giansoldati of Il Messaggero about Vice President JD Vance's April invocation of just war theory to defend U.S. military action against Iran.

The Pope's Position

Leo pointed to his own encyclical, Magnifica Humanitas (Magnificent Humanity), which argues that just war theory has "too often been used to justify any kind of war" and is "now outdated." His argument: the theory was developed in an era that couldn't conceive of modern weapons and their capacity for mass civilian destruction.

"The just war theory comes from centuries ago, from a time when people could not imagine the weapons and destructive capacities that exist today," Leo said, according to Catholic Culture.

He's also made overcoming just war theory a formal agenda item — scheduling it as a central theme at the Vatican's consistory, a summit of cardinals set for June 26-27.

The Vance Clash

Back in April, Vance didn't just invoke just war doctrine — he told the pope to "be careful" when talking about theology. Vance argued there is "more than a 1,000-year tradition of just war theory" that the pope was dismissing.

Trump piled on afterward, calling Leo "weak" on war in a Truth Social post.

Leo did not back down then. He is not backing down now.

Earlier this year, Leo had also called Trump's threat that "there will be no civilization left in Iran" unacceptable. Trump responded by calling the pope "weak and terrible on foreign policy." According to Anadolu Agency, the exchange drew rare public pushback even from Italian Prime Minister Giorgia Meloni — a political ally of Trump — who called the remarks directed at Pope Leo "unacceptable."

Other Remarks From the Flight

Leo said he is "worried for Ukraine" and called for continued negotiations to end a conflict now in its fourth-and-a-half year. He acknowledged U.S. mediation efforts and noted Putin's recent refusal to meet with Ukrainian President Volodymyr Zelenskyy as a specific obstacle.

On Lebanon, Leo said the situation remains "very complex" as Israel continues operations in the south. He said he is in contact with Lebanese religious leaders he met during his November visit.

He addressed clerical sexual abuse — which he will discuss directly with victims during the Spain trip — calling it an "open wound."

According to Catholic Culture, he also mentioned rapper Bad Bunny, who is performing in Spain during the papal visit. He said he would cheer for the United States in the World Cup, then noted that "Prevost" — his birth name — is for Madrid.

Significance

Leo's remarks come at a moment when Washington's Iran strategy is under pressure on multiple fronts — frozen asset disputes, missile exchanges over the Strait of Hormuz, and a humanitarian crisis the UN says has left over 6 million newly hungry. The Catholic Church's formal opposition to the war's theological justification carries weight with about 1.4 billion Catholics worldwide, including a significant portion of the U.S. military, the U.S. Congress, and populations in key Gulf and European allied nations.