Leo’s episcopal allies in the United States have made clear that the pope was thinking about Iran in the months before the encyclical’s release, on May 25. On April 10, Leo posted on his official X account, “God does not bless any conflict. Anyone who is a disciple of Christ, the Prince of Peace, is never on the side of those who once wielded the sword and today drop bombs.”
In response, Vice President JD Vance, who is Catholic, cited just war theory at a college campus speech. “When the pope says that God is never on the side of people who wield the sword, there is more than a 1,000-year tradition of just war theory. We can, of course, have disagreements about whether this or that conflict is just.” (Mr. Vance, at a later commencement speech at the U.S. Air Force Academy, stepped back from his criticism and praised the encyclical and the call for an update of just war principles given new technologies in warfare.)
Central to the church’s critique of the Trump administration’s approach to the war in Iran is that it has offered contradictory, murky and mercurial justifications for the conflict. Some of the administration’s arguments included elements of just war principles, such as the idea of an imminent nuclear threat from Iran. But Leo and his American allies argue there is almost no justification for war without exhausting dialogue, diplomacy and forgiveness. War can be morally legitimate only in self-defense or in extreme circumstances to repel evil in the world.
Overhauling just war teaching will be among the top issues to be discussed on Friday and Saturday at a consistory, or meeting of the pope’s cardinals, at the Vatican, according to Vatican News, the Holy See’s official outlet. The cardinals should not pull their punches. The moment urgently calls for new guidance, not just discussion. In reformulating the church’s view of war, the stakes for Catholicism, the United States and the world are high, and the Vatican needs to get this right. The universal church, with millenniums of moral reasoning and clergy on the ground in virtually every conflict zone, is uniquely situated to articulate a new intellectual framework on just war theory — especially as A.I. increasingly automates decisions on the battlefield.
The answer is deceptively simple. Leo, his papal predecessors and his contemporary brethren are calling for returning to Christian roots, with one simple concept: War is fundamentally antithetical to the Gospel of Jesus Christ.
