Since the atom bombings of Japan in 1945, the Catholic Church has urged all nations to abandon nuclear weapons and weapons  of mass destrucion.

In the encyclical “Pacem in Terris”, immediately after the Cuban Missile Crisis in 1962,  Pope St. John XXIII wrote: “People are living in the grip of constant fear. They are afraid that at any moment the impending storm may break upon them with horrific violence. And they have good reasons for their fear, for there is certainly no lack of such weapons. While it is difficult to believe that anyone would dare to assume responsibility for initiating the appalling slaughter and destruction that war would bring in its wake, there is no denying that the conflagration could be started by some chance and unforeseen circumstance.”

In 1968, Pope Paul VI urged in the name of all humanity, the “total ban on nuclear weapons” and “general and complete disarmament.” 

In  2010, Pope Benedict XVI stated: “I encourage the initiatives that seek progressive disarmament and the creation of zones free of nuclear weapons, with a view to their complete elimination from the planet.”

In 2019, Pope Francis wrote  “the use of atomic energy for purposes of war is today, more than ever, a crime not only against the dignity of human beings but against any possible future for our common home…The use of atomic energy for purposes of war is immoral, just as the possessing of nuclear weapons is immoral… We will be judged on this.  Future generations will rise to condemn our failure if we spoke of peace but did not act to bring it about among the peoples of the earth.  How can we speak of peace even as we build terrifying new weapons of war?”

Pope Leo continues this message. In 2025 he said “The situation in Iran and Israel has deteriorated gravely, and in such a delicate moment, I would like to renew strongly an appeal to responsibility and reason. The commitment to creating a safer world, free from the nuclear threat, should be pursued through respectful encounter and sincere dialogue, to build a lasting peace, based on justice, fraternity and the common good. No-one should ever threaten the existence of another.”

He continually urges nuclear disarmament. In 2026 in his Message for World Day of Peace he lamented the confrontational logic now dominating global politics:

“In the relations between citizens and rulers, it could even be considered a fault not to be sufficiently prepared for war, not to react to attacks, and not to return violence for violence. Far beyond the principle of legitimate defense, such confrontational logic now dominates global politics, deepening instability and unpredictability day by day. It is no coincidence that repeated calls to increase military spending, and the choices that follow, are presented by many government leaders as a justified response to external threats.  The idea of the deterrent power of military might, especially nuclear deterrence, is based on the irrationality of relations between nations, built not on law, justice and trust, but on fear and domination by force.”

In a recent talk Pope Leo said: “ The current situation requires that everything possible be done to avert a new arms race that would further threaten peace among nations. It is more urgent than ever to substitute the logic of fear and distrust with a shared ethos capable of guiding choices towards the common good and to make peace a treasure to be cherished by all.”