If You Want Peace, Prepare for War: Deterrence Today

Si vis pacem para bellum – “If you want peace, prepare for war.” This famous saying which goes back to Vegetius is unfortunately as relevant in the 21^st century as it was in the 4^th when he wrote his treatise on warfare.^[1] Except among the most extreme pacifists, there has been consensus for centuries on the right of all societies to defend themselves. Yet, it is understandable that many sides have serious reservations when it comes to thinking through a defense that might involve the use of nuclear weapons to fend off a militarily superior opponent.

On several occasions, the Catholic Church has addressed the ethical challenge posed by nuclear arms as weapons of mass destruction. Shortly before the signing of the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) in 1968, Pope Paul VI called on the governments of the negotiating states to “put an end to the nuclear arms race.”^[2] The United States Conferences of Catholic Bishops examined the subject in greater depth.^[3] In the early 1980s, the Catholic Church under Pope John Paul II adopted a compromise position. It accepted nuclear deterrence, but condemned the use of nuclear weapons as immoral.^[4] There is an inherent contradiction here, however, as deterrence is not credible unless there are feasible plans to actually use the weapons.

The legitimacy of nuclear deterrence itself has been questioned by experts on international law, on the basis that terrorizing the civilian population is incompatible with international humanitarian law. In 1996, the International Court of Justice (ICJ) issued an “Advisory Opinion on the Threat or Use of Nuclear Weapons”. In this document, the ICJ stated that it could not “reach a definitive conclusion as to the legality or illegality of the use of nuclear weapons by a State in an extreme circumstance of self-defence, in which its very survival would be at stake.” (Presumably this meant the survival of the population and not just the structures of a state.)^[5]

Pope Francis has now dropped the ambiguity of his predecessors’ position, which was that the possession alone of nuclear weapons for deterrence purposes was acceptable. He stated in 2017 that “the threat of their use, as well as their very possession, is to be firmly condemned,” given the risk of accidental or erroneous detonation.^[6] That same year, the United Nations (UN) convened the conference that adopted the Treaty on the Prohibition of Nuclear Weapons (TPNW). It came into force on 22 January 2021 with 86 signatories, of which 51 had ratified the treaty by that date. Obviously, these did not include nuclear-weapon states or their allies.^[7] Nuclear weapons therefore continue to exist, both in NATO’s arsenal and in that of its self-appointed adversary, Russia. But the issue is still how to defend oneself against an overpowering enemy, in particular one who has nuclear weapons.

In general terms, how do you deter an overpowering, expansionist opponent from attacking a militarily weaker state? Such an opponent will rarely be swayed by ethical arguments. Many examples from history tell us what happened in cases when the small state lay along a strategic axis of attack – from the sad plight of the Melians, whose island stood between Athens and Sparta in the Peloponnesian War, to the fate of “neutral” Belgium in the two world wars of the 20^th century. So persuasion with purely ethical arguments is not a promising approach.

Deterrence

What remains is to seek to “persuade” through deterrence, i.e. with threats. These can take two forms. The first – which is hardly an option for smaller, weaker states acting alone – is to make it clear to the enemy that an attack will not succeed due to one’s own defensive strength. This can be called deterrence by denial. The other is to threaten consequences that the enemy does not want to suffer, i.e. deterrence by punishment.

Clausewitz made a wise observation: such threats require the potential to be transformed into action in order to be credible.^[8] And even if they are, an enemy may not be deterred. In the 1930s, the French military author Pierre Faure thought that Germany could be deterred from carrying out aerial attacks on its enemies in a future war. If France were to build up a bomber force that was larger than that of its enemies,

“[t]he fear of terrible retaliation [against their aggression], without precedent in history with its human hecatombs [of dead], would certainly make those on the other side of the Rhine think before they undertake a new war.  If the German people knew that an attack by its army on France would signify the probable and immediate destruction of twenty of its largest cities and the population they contained, it would seem doubtful that the German government would take this risk. […] 400 aircraft, […] capable of annihilating twenty German cities, the bridges of the Rhine, important railway stations and the great industrial centres, are the best guarantee of peace that we could own.”^[9]

As we all know, he was wrong. German air raids on enemy cities still took place, even against enemies such as the United Kingdom, who in return reduced German cities to rubble and ash.

With the advent of nuclear weapons, however, Faure’s deterrence calculation began to look realistic. Following the destruction of Hiroshima and Nagasaki, it was believed that the horror created by their use would be sufficient to deter future wars of aggression. In fact, the initial impetus to develop the atomic bomb was motivated by deterrence. Einstein had warned in August 1939 that German physicists could be working to make such a bomb. This fear was shared by two nuclear physicists who had escaped to England from the persecution of Jews in the German Reich – Otto Frisch and the Austrian Rudolf Peierls. In February 1940, just five months after the German attack on Poland and the associated declaration of war by Britain and France, they wrote to the British government urging the development of nuclear weapons. Their calculations showed that in principle, such a weapon could be built. As “no shelters are available that would be effective and that could be used on a large scale. The most effective reply would be a counter-threat with a similar bomb. Therefore it seems to us important to start production as soon and as rapidly as possible, even if it is not intended to use the bomb as a means of attack.”^[10]

Thus the development of nuclear weapons began with the intention of deterrence, even though their first use did not follow threats of punishment: Japan was not warned before the atomic bombs were dropped in August 1945. Only after the destruction of the two cities could it be hoped that in future the threat of using nuclear weapons would be enough to achieve what even Faure’s planned four-hundred-strong fleet of bombers had failed to do, namely to deter an enemy from attacking altogether. The atomic bomb took destructive power and reach to a whole new level, never known before. In some circles, the belief in this deterrent effect has been so deep that in France it has been called an arme de non-emploi – a “weapon of non-use”. Then came the hydrogen bomb, which was more destructive by several orders of magnitude. First tested by the United States in 1952, it is now probably present in the arsenals of all nuclear powers.

Tactical nuclear weapons under conditions of conventional inferiority

The optimism associated with nuclear weapons, particularly in the United States, did not diminish with the realization that (from an American perspective, “smaller”) wars could still take place. U.S. President Truman, at least, believed he could save American soldiers’ lives by using the first two atomic bombs. Defenders of this decision worked out that their use in Hiroshima and Nagasaki had “saved half a million (American) lives”.^[11]

From the 1950s onward, America’s nuclear weapons laboratories developed a whole range of “tactical” nuclear weapons. These were intended to take the place of a large number of conventional weapons, and to fend off the Warsaw Pact’s superior force of tanks, aircraft and ships. Nuclear devices were meant to block tactically dangerous invasion points along the Iron Curtain. If this was not sufficient to defend against attackers, short and medium-range missiles were to be used against advancing tanks on West German soil, or on the northeastern borders of Italy or Turkey. Attacking bomber squadrons were to be shot down by surface-to-air missiles, and ships sunk by nuclear anti-ship weapons. To the present day, nuclear depth charges are meant to deny Russian submarines access to the Atlantic and so prevent them from attacking countries bordering that ocean. All of this created the hope that attacking conventional forces could be defeated with the help of nuclear weapons. In turn, it was necessary for the Warsaw Pact leadership to be aware that the West had this capability; denying the former any possibility of victory was a key factor in deterring them.

But what would be left of Central Europe if it became a nuclear battlefield in this way? This question was of particular concern to the West Germans. The Anglo-American strategy of the 1950s and 1960s envisaged the use of nuclear weapons in the European theater of war to make up for NATO’s numerical inferiority in conventional forces. Already in the late 1950s this met with resistance in West Germany. Shortly after the Bundeswehr was founded in 1955, it took part in NATO exercises with scenarios involving the use of tactical nuclear weapons on German territory, in which millions of Germans would perish. Cynics at the time coined a saying: “The shorter the range, the deader the Germans.” [sic!] The tactical use of nuclear weapons – especially short-range weapons and atomic demolition munitions deployed along the borders between NATO and the Warsaw Pact – would have resulted in high numbers of casualties among the populations of these areas, due to the destructive force of the explosions and the ensuing radiation. German defense experts began to explain to their allies that tactical nuclear weapons were unacceptable for the defense of Alliance territory. Any attempt by NATO to achieve a tactical victory over invading Warsaw Pact forces using nuclear weapons would have devastated large parts of their country.

The Great Debate

Strategic nuclear weapons are those which, in the extreme case, would have been used against cities in the Soviet Union. But these too did not resolve the issue as satisfactorily as had been initially thought. After the USSR conducted its first nuclear test in 1949 and started developing its own nuclear weapons, the question arose, directly echoing the Frisch-Peierls Memorandum: in the future, would Soviet nuclear weapons by their very existence deter the use of nuclear weapons by Americans in a Soviet war of aggression against Western Europe? Did this mean that nuclear weapons are only good for deterring the use of other nuclear weapons? Would this make the conventionally inferior NATO, founded in the same year, weaker, despite its nuclear weapons, if the USSR and its allies were to attack?

It took a few more years before the Soviet Union also had its own viable nuclear weapons, and then a few more until it had the capability not only to reach Western Europe but also strike the United States with missiles. For almost a decade, the nuclear weapons strategy of the West was still to threaten nuclear punishment by bombing the cities of the Soviet Union and its allies. But once the USSR began to develop intercontinental ballistic missiles in 1957, doubts arose on both sides of the Atlantic as to whether one could count on the US to use nuclear weapons in defense of Europe. Would a president in the White House really risk a counterstrike against Chicago or New York? This was the “Great Debate” of the following years.

The simplest response to this dilemma was the French one. President Charles de Gaulle decided that France, as a sovereign nation, must develop its own nuclear weapons. The governments of Sweden and Switzerland had similar thoughts, and – under different conditions – so did Chairman Mao in the People’s Republic of China, who was increasingly shaking off the Soviet tutelage of his country. In the Federal Republic of Germany, however, people were aware of how negatively the new allies in the West would perceive any independent development of nuclear weapons so soon after the end of the Third Reich, not to mention the exorbitant costs this would have entailed. As Defense Minister, Franz Josef Strauß flirted with the idea of a European nuclear force. This was supported by his colleagues in Rome and – before de Gaulle’s return to power in France in 1958 – in Paris. Not least with a view to such a development, the Treaties of Rome were signed at Easter 1957, including Euratom, the Treaty on the European Atomic Energy Community. At the same time, a Franco-German research institute was set up in Saint-Louis, where German scientists associated with Wernher von Braun had been developing missile technology together with French colleagues since 1945.^[12]

This project failed in part because of de Gaulle’s insistence on national strategic sovereignty and rejection of further European integration needed to create a political authority at the head of a united Europe that could order the use of nuclear weapons. It also failed due to resistance on the part of the other nuclear powers to the further proliferation of nuclear weapons. Various projects were discussed or even realized, such as the Multilateral Force (MLF), which actually went to sea from 1964 to 1965 with the American ship USS Claude V. Rickets, crewed by officers and sailors from various NATO member states and equipped for nuclear missiles. A current example is the deployment of American B61 nuclear bombs by suitable aircraft (F‑35A) in the possession of some NATO states. But all of these projects are still subject to a U.S. veto. This means that if a U.S. president is reluctant to use nuclear weapons, then European allies cannot use them either – with the exception of the United Kingdom, which tested a nuclear explosive device as early as 1952, and France, which carried out its first test in 1960.

The United States and Great Britain together did everything in their power to prevent any further proliferation of nuclear weapons. This was achieved partly through secret American promises to come to the assistance of friendly states in the event of an attack – such as allies Japan and South Korea in the Pacific or neutral Sweden in Europe. Furthermore, NATO and its allies began to consider how nuclear weapons could be used in the event of a Warsaw Pact attack without destroying large areas of European NATO territory or exposing them to a conventional world war. The theme of these deliberations, which still take place today in NATO’s Nuclear Planning Group (NPG) (in which France refuses to participate), is captured by the title of a famous book at the time: “Thinking the Unthinkable”.^[13]

First use to stop the war

But what other alternatives might there be to reducing Central Europe to ashes or destroying cities with bombs or long-range weapons? How to avoid a situation where the only ways to counter an attack by the Warsaw Pact were with conventional armed forces, with tactical nuclear weapons that would turn the attacked region into a radioactive pile of rubble, or with strategic nuclear weapons?

There was a return to the rationale behind the use of nuclear weapons against Hiroshima and Nagasaki, which aimed at ending/stopping a war started by the enemy. The reasoning was as follows: if the enemy were to attack NATO despite American (and British and French) possession of nuclear weapons, then this could be due only to the (mistaken) assumption that the three nuclear powers would not resort to using these weapons because they wanted to avoid the nuclear battlefield option, even though their conventional means alone were insufficient to repel the attack. In the event of such an attack, deterrence would have failed due to a lack of credibility. So how to restore credibility vis-à-vis the will to escalate? And how to do so without immediately going to extremes – i.e. targeting major cities with nuclear weapons – which in all probability would not stop the war, but instead lead to the most extreme retaliatory measures – counter-strikes on major American cities? This prospect alone would result in U.S. self-deterrence.

Defense analysts had thought about this in various contexts. At the beginning of the 1960s, the British came to the conclusion that the first use of nuclear weapons by NATO – i.e. by the U.S. or the UK – should simultaneously threaten further escalation, yet not cause the enemy to launch a completely desperate counter-attack. It had to be made clear that NATO no longer hesitated to use nuclear weapons, but was nevertheless willing to negotiate and stop the war. At the end of 1969, the NPG agreed that such a first strike should be targeted at enemy forces and transport hubs outside densely populated areas, but not directly at cities. The problem was that this required the nuclear weapons employed to have a precision which was not available in the 1960s. However, only a few weapons would be needed for the purpose of re-establishing deterrence, as the idea of completely repelling an attack at tactical level had now been abandoned. With a limited use of nuclear weapons aimed at stopping the war, it would not be necessary to defeat the enemy tactically, but only force him to rethink.^[14]

Precision missiles were developed for this purpose in the 1970s. These included 572 “Euromissiles” – cruise and ballistic missiles, which NATO in December 1979 decided to station in Europe in the following years. They replaced 1400 less precise nuclear weapons, which were scrapped from 1983. All in all, this was about limiting the destructive power of a nuclear first or second strike by NATO. Contrary to what Soviet military leaders and representatives of Western protest movements of the early 1980s claimed, it was not an indicator of the NATO member states’ increasing bellicosity. Nevertheless, who wants peace must be able to credibly demonstrate how he can mount an effective defense

Changing ethical attitudes

In the background, there was also a progression in Western attitudes toward the killing of civilians. Despite longstanding efforts by humane theologians, philosophers and legal experts to contain war and afford better protection to civilians, the Second World War brought about unprecedented human suffering. Millions of civilians were killed in Asia and Europe, more than in any previous war.^[15] It makes no sense to balance the numbers of victims on the respective sides, but it is a fact that the British and American air forces’ bombing of enemy cities also contributed to the horrendous tally. This strategy continued in the subsequent wars in Korea and Vietnam.

It was not until the anti-nuclear protests in Europe in the late 1950s and early 1960s, followed by similar demonstrations against the Vietnam War, that attitudes changed in the West. The intentional targeting of civilians, especially in cities, was increasingly condemned. This change took concrete form with the adoption of the Additional Protocols to the Geneva Conventions in 1977, which declared such acts to be war crimes. This rekindled reservations about the existing doctrines on the use of nuclear weapons. Leading nuclear weapons theorists now argued that at least a nuclear first strike should not be aimed at large population centers, but at military targets, even though there was no longer any intention of repelling a Warsaw Pact attack entirely with tactical nuclear weapons.

This was NATO’s deterrence concept at the end of the Cold War: Since it would not be possible to deter an attack by the Warsaw Pact completely, nor to repel it conventionally or with tactical nuclear weapons, the intention was to use a limited number of precise medium-range weapons to target the armed forces and military infrastructure without seeking a military victory. Rather, the aim was to deliver a big enough shock to make the enemy realize he was mistaken if he had assumed that NATO would not defend itself resolutely and, if necessary, employ nuclear weapons. But the enemy should be given one last chance to back down. In this way, deterrence was to be restored.

The (first) Cold War came to an end in 1991 with the dissolution of the Warsaw Pact, and in the following years both sides disarmed many of their nuclear weapons. The “Euromissiles” – the medium-range missiles – were completely removed from Europe, as were tactical nuclear weapons of all kinds.

Deterrence today: nuclear and non-nuclear strategic weapons

How should we counter an expansionist Russia today? Should we return to the arsenal of the 1980s and relinquish all the hard-won arms control agreements that came with the end of the Cold War? Apart from the aforementioned B61 freefall bombs held by individual allies, whose use would have to be authorized by the U.S. president, only France still has non-strategic nuclear weapons (air-to-surface missiles) that could be used to restore deterrence once a Russian attack has begun.

In the meantime, there are new weapons systems and therefore perhaps new possibilities for deterrence. Today, we can ask whether a shock to restore deterrence might be delivered in a different way than with nuclear weapons, for example. Greater precision of ballistic and cruise missiles means that it is no longer necessary to compensate for a lack of accuracy with greater explosive power. Developments in artificial intelligence and cyberspace combine with aeronautics here.^[16] Moreover, it is much more likely that a U.S. president or an American military commander-in-chief would order NATO to use very precise conventional weapons for the defense of Europe than nuclear weapons. Accordingly, the announcement that conventionally armed, non-nuclear cruise missiles, ballistic missiles and hypersonic weapons will be deployed in Germany from 2026 is to be welcomed. These lessen the possible collateral damage and also pose fewer ethical problems than nuclear alternatives. Yet, they still have the potential to deter attacks on NATO allies, without, however, making nuclear deterrence entirely redundant. An in-depth examination of the issues outlined in this article may make large sections of the population feel uncomfortable, especially after a long period of peace. But for the foreseeable future, this is unavoidable as part of a discussion about warfighting capability and the threat posed by a violent, openly hostile Russian state.