Vatican City: The Catholic Church’s teaching on war has steadily moved toward a stronger rejection of violence, with recent Popes warning that modern weapons have made it almost impossible to justify war as a means of justice.
From the time of Pope Benedict XV, who described the First World War as a useless slaughter, Popes have consistently appealed for peace. Pope Pius XII also worked to prevent the outbreak of the Second World War, though his efforts were ultimately unsuccessful.
A major shift in thinking came with Pope John XXIII, who in his 1963 encyclical Pacem in Terris said that in the atomic age, it is nearly impossible to consider war as an instrument of justice. This marked a turning point as the destructive power of modern weapons began to reshape moral reflection.
The message was strongly echoed by Pope Paul VI, who famously told the United Nations, No more war. Later, Pope John Paul II repeatedly appealed to world leaders to avoid conflicts, especially in the Middle East, though many of his warnings went unheeded.
The Church’s position, reflected in the Catechism of the Catholic Church, still allows for self defense but sets very strict conditions. These include the need for serious harm, the failure of all peaceful options, and the requirement that the use of force should not cause greater damage than the threat itself. In today’s world of advanced weapons, these conditions are increasingly difficult to meet.
During his pontificate, Pope Francis strongly warned against attempts to justify war. In his 2020 encyclical Fratelli tutti, he said that modern wars are often defended using misleading arguments, while their consequences bring massive suffering, especially to civilians. He stressed that humanity now has immense destructive power but lacks the wisdom to use it responsibly.
Continuing this message, Pope Leo XIV has made peace a central theme of his leadership. Speaking during a prayer vigil on April 11, he warned against a world driven by threats and displays of power. He called on people to reject violence and instead choose dialogue, understanding, and respect for human life.
As conflicts continue to grow and military spending rises worldwide, Popes’ consistent message remains clear. War is no longer seen as a solution, but as a danger that risks causing greater harm than good, especially in an age shaped by powerful and destructive technologies.