Opinion

The future of the world is at a critical point. Today, 103 states are involved in wars throughout the Middle East, in Ukraine, Sudan, Myanmar, Yemen, the Democratic Republic of the Congo and in silent wars in many other countries. Pope Francis said “the Third World War is being fought piecemeal” to describe this dangerous situation of widespread and almost endemic conflict, without precedent since the end of the second World War.In his recent encyclical Magnificent Humanity, Pope Leo XIV states that the Church is no longer a believer in “the just war theory”, which has been church teaching since St Augustine developed it more than 1,600 years ago.In paragraph 192, he writes that “the ‘just war theory’ which has all too often been used to justify any kind of war is now outdated”. READ MORENot only is it outdated, but “no algorithm can make war morally acceptable” and the use of force ultimately reflects a “relational poverty”.In these words he presents a challenging vision and a new way forward to the people of Earth: “It is not atomic weapons that generate peace, but disarmament. This truth, which seemed clear in past decades when we witnessed a nuclear de-escalation, has been obscured by a race to armament that today frightens and terrifies us all.” The pope’s condemnation of the just war theory challenges both international and humanitarian law criteria on which they are based. Present international law restricts the use of force to two key exceptions: self-defence against armed attack or authorisation by the UN Security Council, neither of which can justify the war unleashed by the US and Israel on Iran.Humanitarian law governs the conduct of war by banning war crimes and limiting total war, where those who wage war disregard human lives and other resources in their aim for complete victory and total annihilation of their declared enemies.[ No more sheltering or iodine tablets: Why are we getting a new nuclear emergency plan?Opens in new window ]Pope Leo’s stance marks a return to early Christian teaching. The first three centuries of the Christian era marked a time when Christians generally adopted a non-violent pacificist position – even refusing to join the Roman legions.This changed significantly when Christianity became the state religion of Rome in the 4th century. The previous pacifist stance, preached by Jesus of Nazareth and adopted by the early leaders of the Christian movement, was replaced by the acceptance of war as a necessary evil, and development of the “just war” theory to rationalise this change.French academic René Girard has written that “beginning with Constantine, Christianity triumphed at the level of the state and soon began to cloak with its authority persecutions similar to those in which the early Christians were victims”. As has happened throughout history, and is still persisting, those persecuted in the past become the persecutors of the present.Worse was yet to come when, in 1095, at the Council of Clermont, Pope Urban II declared that some wars could be declared not only “just” but also “holy”. This papal sanctioning of the concept of a “holy war” prompted a radical transformation in the ideology of war which led to the Crusades and continues down to our present day, flourishing in the US Maga movement.[ Bellicose, vengeful, unapologetic: Why Pete Hegseth sees moral purpose in war as weaknessOpens in new window ]In his 2026 Palm Sunday homily, Pope Leo repudiated Pope Urban’s teaching and redirected the Christian position on war back to its origins. He was responding to the US secretary of war, Pete Hegseth, who called on God to bless the US Iranian crusade and to kill the “wicked” enemies “who deserve no mercy” and should be “delivered to eternal damnation”.Pope Leo rebuked such misuse of Biblical language to justify the indiscriminate use of violence in the Iranian offensive. “Jesus is the King of Peace, who rejects war, whom no one can use to justify war,” said the pope. “He does not listen to the prayers of those who wage war, but rejects them.” He went on to recall the prophet Isaiah’s words: “Even though you make many prayers, I will not listen: your hands are full of blood.”Due to the destructive capacity of modern technology, including the use of tactical nuclear armaments and AI to direct war strategy and choose targets, the concept of a just war is, from a Christian perspective, unjustifiable by any ethical standards. The race to world rearmament fuelled by the arms industry is now almost unstoppable.The idea of a negative peace based on the irrational fear of war must be superseded by that of a positive peace where the social, cultural and economic conditions that give rise to war are eliminated. As John F Kennedy put it: “Mankind must put an end to war before war puts an end to mankind.”Brendan Butler is a theologian and author of My Story, by Jesus of Nazareth