Pope Leo XIV buries the doctrine of “just war” and overturns Catholic teaching

In his first encyclical, Pope Leo XIV rejected the theory of "just war," a principle used for centuries by the Catholic Church to determine under what circumstances a conflict could be morally justified. This stance marked a major turning point in Catholic doctrine on war.

The text, entitled Magnifica Humanitas ("Magnificent Humanity") was published Monday at the Vatican. In it, the Pope asserts that this theory, present in Christian thought since at least the 5th century, is now "outdated".

"The theory of 'just war', which has been used far too often to justify all kinds of war, is now outdated," the Pope wrote in this document considered the first major doctrinal text of his pontificate.

Pope Leo XIV believed that humanity now possesses more suitable tools for resolving international conflicts, including "dialogue, diplomacy, and forgiveness." The first American pope in history, he also called for global regulation of artificial intelligence systems and offered a particularly strong apology for the Catholic Church's historical role in supporting the transatlantic slave trade.

According to American Cardinal Blase Cupich, a close ally of the Pope and present at the Vatican during the presentation of the encyclical, Leo XIV is concerned about the way this doctrine has been used by political leaders to justify military interventions.

The theory of just war is still invoked in some contemporary geopolitical debates. Reuters notes, in particular, that US Vice President JD Vance referred to it to defend a war against Iran.

This stance could have significant consequences for the role of the Catholic Church in international debates related to armed conflicts. By breaking with a centuries-old doctrine, Leo XIV asserted a much more radical position in favor of pacifism and the diplomatic resolution of crises.