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The End of the "Interlude" – Nuclear Deterrence in the Light of Roman Catholic Social Teaching

Pope Francis’ current input into the debate

On November 10/11, 2017, the Dicastery for Promoting Integral Human Development – a new central body created by Pope Francis – organized an expert symposium in the Vatican on “Prospects for a World Free of Nuclear Weapons and for Integral Disarmament”. During the conference, the pope invited participants to an audience. In the Clementine Hall, he gave an address in which he welcomed the fact that “in a historic vote at the United Nations, the majority of the members of the international community determined that nuclear weapons are not only immoral, but must also be considered an illegal means of warfare. This decision filled a significant juridical lacuna, [... but] even more important is the fact that it was mainly the result of a ‘humanitarian initiative’ sponsored by a significant alliance between civil society, states, international organizations, churches, academies and groups of experts.”1

Pope Francis reaffirmed this position – as had been generally expected – in the context of his visit to Japan at the end of November 2019. On his return flight, he declared in a press conference: “Hiroshima was a true human catechesis on cruelty. Cruelty.” He added that moral condemnation of the use and possession of nuclear weapons “must also be included in the Catechism of the Catholic Church”2. Ever more urgent in tone, but without going into further detail, the pope indicated that he wished the Roman Catholic Church to show a greater degree of commitment in its rejection of nuclear weapons, comparable to developments in regard to capital punishment. As he explained in his message from the Peace Park in Nagasaki, this has a fundamental basis in the Church’s tradition: “[T]he Catholic Church is irrevocably committed to promoting peace between peoples and nations. This is a duty to which the Church feels bound before God and every man and woman in our world. We must never grow weary of working to support the principal international legal instruments of nuclear disarmament and non-proliferation, including the Treaty on the Prohibition of Nuclear Weapons” (author’s emphasis).3

The history of the current debate

For many people, it may come as a surprise to find that the pope and the Holy See are strongly committed to outlawing nuclear weapons. But even in Dès le début of August 1917 – the first papal “Peace Note” of the 20th century, addressed “to you who at this tragic hour direct the destinies of the warring nations” – Pope Benedict XV set out a number of points as the basis for a “just and lasting peace”. It states: “First of all, the fundamental point must be that the material force of arms must be replaced by the moral force of right; hence there should be a just agreement by all for the simultaneous and reciprocal reduction of armaments, in accordance with rules and guarantees to be established, to the extent necessary and sufficient to maintain public order in each state.”4 From that time onward, these concerns remain a constant theme in Roman Catholic teachings on peace.

The magisterium of the Catholic Church is consistently and unmistakably skeptical toward the armament efforts of states, even if it holds no pacifist expectations. This attitude becomes much more severe in the case of nuclear weapons. Already in 1954, in his Easter speech in St. Peters Square, Pope Pius XII stressed the urgent need for international understanding by vividly invoking the horror of a nuclear war: “Thus before the eyes of the terrified world lies the vision of gigantic destruction, of vast territories rendered uninhabitable and useless to mankind, in addition to the biological consequences that may be produced, both by mutations induced in germs and microorganism, and by the uncertain outcome that a prolonged radioactive stimulus may have on major organisms, including humans, and their descendants.”5 The Pope thus concretizes an earlier motif which he had unfolded in his Christmas message from 1950 under the impression of an imminent new world war: “Today, in a war which God may prevent, the weapons would have such a devastating effect that they would leave the earth as it were ‘waste and void’ [Gen 1,2; attached as a note in the original, the author], as wasteland and chaos, similar to the desolation not of its original beginning, but of its downfall.”6 Significant enough for the drama of the situation, however, the Pope no longer dares to repeat the statement made shortly after the war that the experience of war had „spurred the longing for peace and the will to work for it“, and „has placed the problem of disarmament at the center of international aspirations with entirely new considerations and with an emphasis never felt before“7. In the Cold War, disarmament efforts take a back seat and bring the doctrine and theory of nuclear deterrence to the fore. It is the encyclical Pacem in terris (April 11, 1963) by Pope John XXIII which gives the topic an unprecedented rank.

The position of the U.S. bishops’ conference: It is important to remember that up to the present day, ethical discussion of security and armament policy has been conducted in the context of the traditional doctrine of just war, both at the level of the papal magisterium and in large parts of Catholic moral theology. However, this does not apply to those groups and movements within the Catholic Church who take a strictly pacifist stance – similar to the so-called historic peace churches (e.g. Quakers, Mennonites) in Protestant Christianity – and who consequently reject the doctrine of just war. Because of this strictly ethical position, the Roman Catholic Church has never been drawn into regarding nuclear weapons and the possibility of atomic self-destruction as an end-of-days phenomenon, as some sections of the Protestant communities and other apocalyptic dystopias do.

The official attitude of the Roman Catholic Church to war was outlined by the U.S. bishops’ conference in 1983 in their pastoral letter The Challenge of Peace: God’s Promise and Our Response, in five points. The American bishops adhere to the traditional view, inasmuch as it ascribes to peoples “a right and even a duty” to “protect their existence and freedom by proportionate means against an unjust aggressor”, and at the same time denies moral legitimacy to any war of aggression.8 With reference to the Second Vatican Council, the bishops underline the crucial importance of the principle of distinguishing between combatants and civilians in acts of war, and the need to observe the criterion of proportionality even in the case of a defensive war: “No defensive strategy, nuclear or conventional, which exceeds the limits of proportionality, is morally permissible.”9

The American bishops also discuss the ethical problems of nuclear deterrence in the light of the criteria developed in the doctrine of just war. They therefore set out these criteria in detail in their pastoral letter and critically reflect on them with regard to the situation in the modern world. These criteria form the ethical foundation of all Church and magisterial pronouncements on the question of nuclear weapons.

The idea of the "interlude"

The Second Vatican Council (1962-1965) has fundamentally renewed the self-image of the Roman Catholic Church and many of its teachings. But none of the innovations fell from heaven, so to speak. They had already started to develop in the Church and in theology. Also with regard to Church doctrine on peace, the Council took up the core elements of the insights associated with the world wars, in particular by directing its attention to the weapons of mass destruction that were now available: “[... A]cts of war involving these weapons can inflict massive and indiscriminate destruction, thus going far beyond the bounds of legitimate defense.”10 According to the Council, the tendency toward total war is an intrinsic characteristic of weapons of mass destruction, which it condemns categorically, due to its destructive consequences, as “a crime against God and man himself”11. The Council saw only one way to counter this danger: “Warned by the calamities which the human race has made possible, let us make use of the interlude granted us from above and for which we are thankful to become more conscious of our own responsibility and to find means for resolving our disputes in a manner more worthy of man. Divine Providence urgently demands of us that we free ourselves from the age-old slavery of war” (author’s emphasis).12

From then on, official teachings on nuclear deterrence would be shaped by the idea of an “interlude granted us from above” so that we might find political alternatives to war. Thus the U.S. bishops, in their 1983 pastoral letter mentioned above, acknowledged that the interlude serves to ensure a certain kind of peace – “our present peace” – and therefore stopped short of a fundamental rejection.13 However, their stated intention was “to reinforce with moral prohibitions and prescriptions the prevailing political barrier against resort to nuclear weapons”. And they urged “negotiations to halt the testing, production, and deployment of new nuclear weapons systems. Not only should steps be taken to end development and deployment, but the numbers of existing weapons must be reduced in a manner which lessens the danger of war.” The bishops conclude: “There is an urgent moral and political responsibility to use the "peace of a sort" we have as a framework to move toward authentic peace through nuclear arms control, reductions, and disarmament.”14 This view does not necessarily imply the abolition of nuclear weapons as the end goal of disarmament, but it is logically compatible with the concept of minimal deterrence. Nevertheless, even in 1983 the bishops did not regard adherence to the deterrence strategy or moral tolerance of nuclear deterrence as being the final word in this matter. They saw it as a conditional acceptance. As they put it: “Deterrence is not a suitable strategy for securing peace in the long term. It is a transitional strategy that can only be justified in connection with an absolute determination to work for arms control and disarmament” (author’s emphasis).15 Also in 1983, in their pastoral letter Gerechtigkeit schafft Frieden (“Justice Creates Peace”), the German Bishops’ Conference (Deutsche Bischofskonferenz) also mentions the Council’s “interlude” – (in German: “Frist”)16 – granted to us from above, which allows a “temporary” toleration of nuclear weapons. This can be described as an “emergency ethics”.17

Talk of an “interlude” was clearly intended to underline the urgency of the political task of disarmament. It served to initiate a process which, by means of arms control and disarmament, had to be geared towards overcoming the strategy of nuclear deterrence. For this reason, “interlude” did not refer primarily to a certain period of time, but to factual conditions that must be fulfilled so that the strategy of nuclear deterrence can be tolerated. These conditions imply, on the on hand, the criteria that apply to war and war planning in general, and on the other hand, the decisive and indissoluble link between a possible temporary acceptance and the political engagement to overcome the strategy of nuclear deterrence. With this in mind, the tolerance of nuclear weapons depends on a political decision, or more precisely, on a judgment on the credibility and seriousness of a targeted disarmament policy which is geared towards an abolition of nuclear weapons. Therefore, the crucial question is: Given the present state of affairs, and looking at the conditions mentioned above, how should this strategy be assessed?

The end of the “interlude”

Developments in the Vatican’s activities: The goal of a nuclear weapon-free world has been present for a long time in papal proclamations. Back in 1965, in his message to mark the 20th anniversary of the dropping of the Hiroshima bomb, Paul VI called for prayer that nuclear weapons might be banned.18 In 1978, in his address to the First Special Session of the United Nations Devoted to Disarmament, he reaffirmed the goal of “completely eliminating the atomic arsenal”19. The step taken by the present pope has continued this line consistently and more specifically by now condemning nuclear weapons in principle. As such, this decision came as a surprise to the public, but it had been in the making for decades, firstly in the deliberations of the Pontifical Academy of Sciences, and also in the context of the diplomatic activities of the Holy See. In 1981, the Academy published a statement on the consequences of using nuclear weapons, followed by a declaration on the prevention of nuclear war in 1982, and finally, in 1984, by a “warning” about the nuclear winter that would result from a nuclear conflict.20 In the 1982 document, the academicians warned that any use of a nuclear weapon, even if limited, carried a great risk of nuclear escalation. Considering the “overwhelming dangers” of nuclear deterrence, they finally conclude: “It is imperative to reduce distrust and to increase hope and confidence through a succession of steps to curb the development, production, testing and deployment of nuclear weapons systems, and to reduce them to substantially lower levels with the ultimate hope of their complete elimination.”21 Once again, the argument focuses not on a general prohibition of nuclear weapons, but on the urgency of a political process that is clearly and unambiguously oriented toward this ultimate goal.

Apart from extensive involvement in efforts to ban nuclear testing, the diplomatic activities of the Holy See are focused mainly on two processes of international diplomacy relating to the problem of nuclear weapons: first and foremost, the negotiations for the Non-Proliferation Treaty (NPT), and secondly the Vienna Conference on the Humanitarian Impact of Nuclear Weapons. The idea for this conference arose in the context of the NPT, and it convened for the third time in 2014. Finally, the negotiations on the conclusion of the Treaty on the Prohibition of Nuclear Weapons (TPNW) should be mentioned. This has now been signed by the Holy See. Archbishop Auza, as Vatican representative, addressed the Ninth Review Conference of the Parties to the Treaty on the Non-Proliferation of Nuclear Weapons. He concluded by quoting Pope Francis, saying that nuclear deterrence and the threat of mutual annihilation cannot be the basis for an ethics of brotherly and peaceful coexistence between peoples and states.22 This statement appears in the pope’s letter to the Austrian Chancellor, Sebastian Kurz, on the occasion of the Vienna Conference on the Humanitarian Impact of Nuclear Weapons.23 For this conference, the Holy See presented an extensive contribution titled Nuclear Disarmament: Time for Abolition.24 According to the American theologian Gerard Powers, this document summarizes the Vatican’s position on the interrelated ethics of the use of nuclear weapons, deterrence and disarmament.25 It could also be said that the text reflects the development of decades of papal teaching. It examines once again a series of arguments for and against nuclear deterrence. Its overall conclusion is that nuclear deterrence can no longer be regarded as a policy that stands on firm moral ground.

First of all, the document refers to the growing consensus on the strict condemnation of any use of nuclear weapons. But it also recalls that the Church has nevertheless provisionally accepted their possession for the purpose of nuclear deterrence, albeit under the condition that this is “a step on the way toward progressive disarmament”. Then follows a decisive statement: “This condition has not been fulfilled – far from it.” “It is now time,” the text continues, “to question the distinction between possession and use [of nuclear weapons].” The time has come for new thinking “to embrace the abolition of nuclear weapons as an essential foundation of collective security.” Now is the time “to affirm not only the immorality of the use of nuclear weapons, but the immorality of their possession, thereby clearing the road to nuclear abolition.”26

It is clear that in his recent statements, the pope has neither changed nor corrected this assessment. Instead, he varies it by placing different emphases, but always with the call to work with all one’s energy for the abolition of nuclear weapons. But how exactly is this position to be understood? According to Gerard Powers, one possible reading is that the Vatican has become a nuclear pacifist. However, he himself offers a more “nuanced interpretation” to consider: that the Vatican has not abandoned its attitude of conditional acceptance or the concept of deterrence as such, but condemns the behavior of the nuclear powers who are evidently not willing to fulfill the conditions of acceptance. Thus it is not the idea of deterrence that is criticized, but rather the morality of its structure as it currently exists.27

Is this “more nuanced” reading accurate? Not quite, if we compare it with the position of the German Commission for Justice and Peace (Deutsche Kommission Justitia et Pax). Or not unless we separate the idea of deterrence from its nuclear realization.

Developments in the Roman Catholic Church in the Federal Republic of Germany: The German Commission for Justice and Peace is run by the German Bishops’ Conference (Deutsche Bischofskonferenz) and the Central Committee of German Catholics (Zentralkomitee der Deutschen Katholiken, ZDK). It represents Catholic institutions and organizations in Germany. As such, given the pope’s position and with regard to the current international political situation, it felt obliged to assess whether it could share his position. A decade earlier, the Commission had given extensive consideration to the issue. In 2008, it published a study with the title “The growing significance of nuclear armaments. A challenge for the ethics of peace and the political sphere”. In this study, the Commission clearly states: “In light of the fact that the continued tolerance which was expressed in the 1980s and which was always combined with appeals to all sides for disarmament was all too often either ignored by those in power or was misconstrued as an acceptance predicated upon the ethics of peace, something which allowed the Church’s position to be exploited, it is particularly important that the Church clarify its position with regard to the ethics of peace. Use of the word ‘continued’ has never been meant to be understood as an attempt to legitimise the simple continuance of deterrence. It should merely serve to retain the necessary political leeway to clearly reduce the dependence of efforts to prevent war on the means of nuclear deterrence and to achieve the strived for full elimination of nuclear armaments and scenarios for their utilisation. Political action must be measured against what it actually does with this leeway” (author’s emphasis).28

Apart from the argument that the “interlude” was deliberately misinterpreted, a trend toward undermining the arms control treaties was already noted in 2008, on which the Commission comments: “[... O]bservation of the trends which are currently evident with regard to nuclear armaments is giving increasing weight to those who argue that this continued tolerance is increasingly losing its justification.”29

In its recent 2019 position paper “Outlawing Nuclear Weapons as the Start of Nuclear Disarmament”, the Commission once again examined the question of whether the strategy of nuclear deterrence can satisfy the necessary criteria of ethics and international law for an extension of the “interlude”. Their verdict is unequivocal: the reasons for rejecting any further continuation now outweigh all others. Not only are the treaty-based pillars of armaments and control policy being eroded, but disarmament successes have obviously been limited by the will of the nuclear powers to maintain the strategy of nuclear deterrence. Its internal contradictions are encapsulated in NATO’s repeated assertion that its policy will remain based on this strategy for as long as nuclear weapons exist. To want a world free of nuclear weapons, but at the same time to declare that the absence of nuclear weapons is the critical condition for ending nuclear deterrence, is only credible if overcoming the strategy of nuclear deterrence begins with banning nuclear weapons. In 2008, the Commission for Justice and Peace had stated relatively vaguely: “An essential step on the road to the elimination of nuclear weapons is ensuring that they do not have any international legitimacy”.30 But now the Commission specifies the necessary steps in sequence: an international ban on nuclear weapons cannot be at the end of a process leading to their actual elimination – it must mark its beginning.31

The political process towards banning and eliminating nuclear weapons

The social teachings of the Roman Catholic Church are by no means intended only for its members. According to a phrase coined by Johannes XXIII, they are addressed “to all people of good will”. In other words, the Church’s arguments should also be understandable to people who may not share the faith of the Church, but who nevertheless see themselves subject to the demands of moral reason as imposed by the human condition. Accordingly, the popes have always addressed the political and public spheres, appealing to recognize and live up to our common human responsibility. Pope Francis is building on the exemplary efforts of all those who are actively committed to the abolition of nuclear weapons: “A world of peace, free from nuclear weapons, is the aspiration of millions of men and women everywhere. To make this ideal a reality calls for involvement on the part of all: individuals, religious communities and civil society, countries that possess nuclear weapons and those that do not, the military and private sectors, and international organizations. Our response to the threat of nuclear weapons must be joint and concerted, inspired by the arduous yet constant effort to build mutual trust and thus surmount the current climate of distrust.”32

In the Roman Catholic Church, new thinking about the strategy of nuclear deterrence has taken root, and some bishops’ conferences have already adopted the pope’s position. As a universal church that embraces and transcends all national contexts, the Church could be a laboratory for political and social debate which then serves as a model. Without such debate, an effective global consensus leading to success in the fight against nuclear weapons cannot be achieved. A global public must put pressure on the governments of the nuclear powers to return to the negotiating table immediately and agree on concrete disarmament steps, instead of gradually terminating or not renewing the existing treaties. The populations of the nuclear powers must not accept the refusal of their governments to sign the ban treaty (TPNW). Rather they should constantly and strongly urge their governments to agree jointly on the controlled elimination of nuclear weapons, instead of developing and perfecting their nuclear capabilities.

In this political process, military personnel play a role that can be fraught with tension and difficulties. Not only, but particularly in the Church, a sense of solidarity with our fellow human beings demands that this role be taken seriously. Military personnel can easily find themselves in a conflict of loyalty with their military and political leaders. This burdens their conscience and affects or even jeopardizes their professional future. In such situations, they need pastoral advice and support. However, it is not only a question of political loyalty and military obedience. Primarily this is about the moral integrity of the individual person, who must reconcile within themselves their duties as a member of the Church and as a citizen on the one hand, and their duties as a member of the armed forces on the other. This can be achieved if they contribute their military expertise to the public and political debate on how to gradually move beyond nuclear deterrence. Deterrence is part of the military craft, but deterrence with nuclear weapons is not.

1 Address by Pope Francis to participants in the international symposium “Prospects for a World Free of Nuclear Weapons”, Friday, November 10, 2017. (accessed 2.6.2020). All texts mentioned or quoted below are available from the internet address Unless noted otherwise, the English text is taken directly from this source.

2 Apostolic journey of Pope Francis to Thailand and Japan. Press conference with the Holy Father on the return flight to Rome, Tuesday, November 26, 2019.

3 Apostolic journey of Pope Francis to Thailand and Japan. Address of the Holy Father on Nuclear Weapons. Atomic Bomb Hypocenter Park (Nagasaki), Sunday, November 24, 2019.

4 (accessed 2.6.2020).(Translated from French.)

5 (accessed 2.6.2020). (Translated from Italian.)

6 For the speech in German, see: Utz, Arthur-Fridolin and Groner, Joseph-Fulko (eds.) (1962): Aufbau und Entfaltung des gesellschaftlichen Lebens: soziale Summe Pius XII. 2. ed. Freiburg, S. 1980-1983, S. 1981. (Translated from German.)

7 Christmas message to the College of Cardinals, 24.12.1946. In: Utz, Arthur-Fridolin and Groner, Joseph-Fulko (eds.) (1962), pp. 1918–1932, p. 1925. (Translated from German.)

8 The Challenge of Peace: God's Promise and Our Response. A Pastoral Letter on War and Peace by the National Conference of Catholic Bishops. May 3, 1983. No. 78. (accessed 2.6.2020).

9 Ibid.

10 Pastoral Constitution on the Church in the Modern World. Gaudium et spes. Promulgated by His Holiness, Pope Paul VI On December 7, 1965. No. 80. (accessed 2.6.2020).

11 Ibid., no. 81.

12 Ibid., no. 81.

13 Cf. The Challenge of Peace, chapter I., B.3. For the text in the following quotation, see no. 194.

14 Ibid., no. 189.

15 Ibid., chapter I., B.3.

16 Gaudium et spes, no. 81.

17 Cf. Deutsche Bischofskonferenz (1983): Gerechtigkeit schafft Frieden. Wort der Deutschen Bischofskonferenz zum Frieden. (Die Deutschen Bischöfe no. 34) Bonn, no. 3.5.2, p. 36. (Translated from German.)

18 Part of the text appears in: Sekretariat der Deutschen Bischofskonferenz (Hg.) (1980): Dienst am Frieden. Stellungnahmen der Päpste, des II. Vatikanischen Konzils und der Bischofssynode. Von 1963-1980. (Verlautbarungen des Apostolischen Stuhls no. 23.) Bonn, pp. 42-43, here p. 43.

19 Message of His Holiness Paul VI to the First Special Sesssion of the United Nations General Assembly dedicated to disarmament, delivered on 6 June 1968 by H.E. Archbishop Agostino Casaroli.

20 Statement on the Consequences of the Use of Nuclear Weapons (1981); Declaration on Prevention of Nuclear War (1982); Nuclear Winter: A Warning (1984).

21 Quotation from “Declaration on Prevention of Nuclear War”. English version available at: (accessed 2.6.2020).

22 Cf. Statement by H.E. Archbishop Bernardito Auza, Apostolic Nuncio and Permanent Observer of the Holy See to the United Nations, New York. Wednesday, April 15, 2015.

23 Cf. Message of His Holiness Pope Francis on the occasion of the Vienna Conference on the Humanitarian Impact of Nuclear Weapons to His Excellency Mr. Sebastian Kurz, Federal Minister for Europe, Integration and Foreign Affairs of the Republic of Austria, President of the Conference on the Humanitarian Impact of Nuclear Weapons.

24 Nuclear Disarmament: Time For Abolition. A Contribution of the Holy See. Permanent Mission of the Holy See to the United Nations and Other International Organizations in Geneva, Vienna, December 8, 2014. Available at:

25 Powers, Gerard. From Nuclear Deterrence to Disarmament: Evolving Catholic Perspectives, in: Arms Control Today, vol. 45 no. 4.

26 Quotations in this paragraph are taken from: Nuclear Disarmament, pp. 4 f.

27 Cf. Powers, op. cit.

28 Deutsche Kommission Justitia et Pax (ed.) (2008): Die wachsende Bedeutung nuklearer Rüstung. Herausforderung für Friedensethik und Politik. (Gerechtigkeit und Frieden no. 113.) Bonn, section 3.1, p. 56. English translation: “The growing significance of nuclear armaments. A challenge for the ethics of peace and the political sphere.”, pp. 56 f. (accessed 2.6.2020).

29 Ibid., section 3.1, pp. 55 f.

30 Ibid., section 3.2, p. 57.

31 Deutsche Kommission Justitia et Pax (ed.) (2019): Die Ächtung der Atomwaffen als Beginn nuklearer Abschreckung. Ein Positionspapier der Deutschen Kommission Justitia et Pax. (Gerechtigkeit und Frieden no. 137.) Bonn, section 6, p. 15. English translation: “Outlawing Nuclear Weapons as the Start of Nuclear Disarmament. A position paper of the German Commission for Justice and Peace.” (accessed 2.6.2020).

32 Address of the Holy Father on nuclear weapons, Nagasaki, November 24, 2019.



Prof. (ret.) Dr. Heinz-Günther Stobbe is ­moderator of the “Just Peace” working group at the German Commission for Justice and Peace. For many years he worked at the Westphalian-Wilhelminian University of Münster (WWU) and the University of Siegen.