How Useful Are Nuclear Weapons in Practice? Case-Study: The War in Ukraine

ABSTRACT The debate about nuclear weapons has been based on abstract notions. The war in Ukraine is a fascinating case-study for testing these decades-old abstract theories. The puzzle can be formulated as follows: what has been the impact of nuclear weapons in the war in Ukraine and what does that tell us about the usefulness of nuclear weapons in general? That question is further split up in three questions: what does this war tells us respectively about nuclear deterrence theory, nuclear responsibility theory, and the theory of nuclear coercion? Each time, the theory will be explained, and matched with the facts on the ground. The answers to these questions will in all likelihood be important for the future of nuclear weapons. All in all, the analysis points out a bleak picture with respect to the usefulness of nuclear weapons. Apart from deterring an attack against the vital interests of a state, nuclear weapons do not seem to provide many benefits apart from many (potential) costs. And even with respect to deterring an attack against the vital interests of a state, it is unclear to what extent nuclear deterrence works.


Introduction
The elephant in the room in the war in Ukraine are Russia's nuclear weapons.For the first time since very long, nuclear weapons occupy a central position in the political debate with respect to the outcome of a war on European territory (Luce 2022).Russia, the largest nuclear armed state in the world, implicitly and explicitly threatened to use nuclear weapons on more than one occasion.There is a risk -be it small -that Russia will effectively use a tactical nuclear weapon, which may on its turn lead to further escalation, possibly a nuclear war.Some analysts even use probability estimates by means of percentages indicating the chance that nuclear war will occur (for a critical view, see Nelson and Montgomery 2022).
At first sight it is unclear what lessons we can draw about the impact of nuclear weapons in this war, also because it is still a moving target; the war rages on; nuclear weapons have not been used (yet).Some argue that nuclear weapons inject a dose of risk

Nuclear Deterrence
Of the three theories, the theory of nuclear deterrence is best known.Deterrence in general (in contrast to coercion, see further) aims to convince another actor not to do something that he has not yet started to do.The nuclear deterrence theory -also known as the nuclear revolution theory (Arceneaux 2023) -posits that the possession of nuclear weapons and the related implicit (or explicit) threat of use of nuclear weapons yields stability, security and peace in world politics (Jervis 1989;Morgan 1977;Waltz 1981).The reason is that political leaders, who are aware of the destructive capacities of nuclear weapons, will think twice before attacking a possessor state of nuclear weapons either with nuclear or conventional means.Unsurprisingly, nuclear deterrence and the effects it is supposed to trigger are also the main reason why states acquire nuclear weapons (Sagan 1996(Sagan /1997)).Today, this is still the main legitimation for the possession of nuclear weapons.
According to the theory, three conditions need to be fulfilled (Sauer 1998).One of the conditions for an effective nuclear deterrent is that the enemy is a rational actor in the sense that he understands the threat.If it is true that Putin has become mad, as claimed by some pundits (Roth 2023) (but which I personally do not believe), it will be harder to make nuclear deterrence vis-à-vis Russia work.Similarly, if the Putin regime is overthrown, a scenario that is regarded as desirable by many in the West and that became imaginable when the Wagner militia marched to Moscow in May 2023, "it is doubtful that the ousted Putin regime would be able to withhold access to nuclear codes for very long, if at all", according to former US State Department appointee Alexander Vershbow (Diaz-Maurin 2023).It then remains to be seen whether Putin's successors will be more "rational" than Putin.
Further, nuclear deterrence theory makes a distinction between vital and more trivial national interests.Only the former is supposed to be protected by the nuclear deterrent.The problem is that it is not always clear -certainly not to outsiders -what the vital interests of a country in practice are (Weldes 1999).
Lastly, the nuclear deterrent should be credible.Problematic is that credibility is basically in the eyes of the beholder.Many observers in the nuclear armed states believe that nuclear deterrence is a credible instrument to guarantee security and peace.Others, however, are convinced that nuclear weapons -especially strategic ones -are too destructive to be used, and that (certainly democratically elected) leaders are of the same opinion and that, as a result, nuclear weapons will not be used and therefore are not credible as a deterrent (Wilson 2013).All three conditions -rationality, vital interests at stake, and credibility -should be fulfilled (Sauer 1998).
Critics contend that proponents of nuclear deterrence exaggerate its positive effects (Lebow and Stein 1995;Wilson 2013; for a different view, see; Gaddis 1986).They admit that in practice nuclear deterrence can work, and that it to a certain extent may have worked in the nuclear era.But they also highlight historical cases when nuclear deterrence has failed: conflicts in which nuclear-armed states have been attacked by nonnuclear weapon states.The latter does not fit with nuclear deterrence theory, especially if vital interests were at stake.The best example is arguably the Yom Kippur War in 1973, when Israel -a known nuclear-armed state at that time -was simultaneously attacked by the armies of Syria and Egypt, two non-nuclear weapon states.Other examples of nuclear deterrence failures are the Falklands war (when non-nuclear weapon state Argentina attacked the United Kingdom) and the Gulf War (when Saddam Hussein launched Scud missiles against Israel).Again, these examples do not match with the theory of nuclear deterrence.
There are also examples of nuclear-armed states that went to war with each other, something you do not expect either on the basis of the theory.The best example is the tandem India-Pakistan.The Kargil crisis in 1999, one year after the nuclear tests in India and Pakistan, resulted in more than 1,000 deadly victims.The latter is formally called "war", the opposite of stability, security and peace, the supposedly outcome of nuclear deterrence.Two years later, a similar crisis in Kashmir also resulted in deadly victims.In 2008, Pakistanis massacred Indians by raiding a hotel in Mumbai.Border clashes abound between both nuclear-armed states.All that does not correspond to what one would expect from nuclear deterrence theory (Kapur 2005(Kapur , 2008)).
Proponents of nuclear deterrence respond that the theory does not preclude smallscale attacks below the nuclear threshold, which points to the so-called stabilityinstability paradox (G.Snyder 1965).The problem with this paradox is that there always exists the possibility of further escalation up to the nuclear level.Advocates of nuclear deterrence theory believe that that level will not be crossed because of nuclear deterrence.Critics refer to the Cuban missile crisis, but also the February 2019 Balakot conflict between Pakistan and India.After an initial Pakistani attack, India -that stood three weeks before national elections -reacted by launching tactical aircraft, immediately followed by Pakistan.A dog fight resulted in the downing of at least one of the planes after which the pilot was captured.Yes, it did not escalate to a nuclear war, but one wonders whether nuclear deterrence advocates still regard events like this as yielding "security, stability, and peace".
In short, nuclear deterrence can work, but it can also fail.It has already failed.As a result, nuclear deterrence is certainly not a panacea for world peace and maybe even not for protecting vital national interests.Problematic is that one serious nuclear deterrence failure may result in nuclear war, and that even a limited nuclear war may yield catastrophic consequences.
The most honest intellectual conclusion is that we simply do not know to what extent nuclear deterrence works or has worked.It is hard to find out why a non-event -in this case a war that has not broken out -happens.The latter can be attributed to different factors, of which nuclear deterrence is only one of them (Wilson 2013).Archival research shows that the USSR in all likelihood has never had the intention to attack Western Europe (Evangelista 2023, 15).If that is the case, the question whether the Western nuclear deterrent has worked becomes even irrelevant.The fact that Germany and France did not fight a fourth war (since the mid-19 th century) after 1945 has more to do with the fact that both became part of the European Community than with France acquiring nuclear weapons.Similarly, the fact that no third world war occurred has probably more to do with the memories of the previous world wars, economic welfare, and globalization than with nuclear deterrence (Mueller 1990).But again, we simply do not know, and both proponents and opponents should not pretend that they do.
That said, even if nuclear deterrence can work and sometimes does work, it comes with security risks such as proliferation and the risk of authorized use, authorized use by false alarm, unauthorized and accidental use by both state and non-state actors.The former Prime Minister of Norway Kjell Magne Bondevik (2022) concludes in the context of the war in Ukraine "that nuclear deterrence is a ridiculously cumbersome tool for dealing with contemporary security challenges".The question is indeed whether a similar or even better level of deterrence without the risk of global catastrophe could not be obtained with other weapons.

Nuclear Deterrence in the War in Ukraine
Advocates of nuclear deterrence argue that the presence of Russian and Western nuclear weapons have injected a dose of prudence on both sides, both on the Russian and Western side (Bell 2024;Dreuzy and Gilli 2022;Freedman 2023;Rose 2022).Nuclear deterrence worked (Hesse 2023;Schepers 2022).Critics are less or not convinced (Adamsky 2023;Bunn 2023;Cocksworth 2022;Giovannini 2022;Johnson 2022;Korb and Cimbala 2022;Ryan 2023;Sauer 2023).Let us elaborate the arguments of both sides.A distinction is made between the Russian and the Western nuclear deterrent, and the absence of a nuclear deterrent by Ukraine.

Russia's Nuclear Deterrent
Proponents of nuclear deterrence argue that Russian nuclear weapons make the Westthe US and NATO -prudent in the sense that the West only backs Ukraine with humanitarian support, intelligence, and sending arms, not with boots on the ground; the West does neither aim to attack Russia and neither wants Ukraine to attack Russia, especially not with Western arms (Hesse 2023;McDermott, Pauly, and Slovic 2023).The West certainly does not want Russia to implode, also because that may lead to a "loose nukes" scenario.Although many pundits in the West want to see Putin removed, others warn that Putin may be replaced by somebody who may be more nationalist and extremist that on its turn may increase the danger of nuclear use.
Advocates of nuclear deterrence argue that the West for instance behaved very prudently after a missile had landed on Polish territory on 15 November 2022.While NATO's article 5 could have been triggered, NATO reacted in a very restraint way (Menon and DePetris 2022).More in general, one could argue that also President Biden is rather prudent, also because of the Russian nuclear arsenal (Freedman 2023, 8;Gramer 2023).One week after Putin's nuclear threats in September 2022, US National Security Advisor Jake Sullivan admitted that the Russian nuclear weapons are "a matter that we have to take deadly seriously" (Rachman 2022b).Similarly, JCS general Mark Milley stated the following: "One thing that was -and still is -on my mind every day is escalation management.Russia is a nuclear-armed state.They have the capability to destroy humanity.That's nothing to play with.We're a big power.Russia is a big power.There's a lot at stake, here, a lot of people's lives.Every move has to be consciously and deliberately thought through to its logical conclusion" (quoted by Stein 2023, 48-49).The US administration in that period apparently "rigorously" prepared for a potential Russian nuclear strike in Ukraine after having picked up communications among Russian officials explicitly debating a nuclear strike (Cooper, Barnes, and Schmitt 2022;Sciutto 2024).
Critics maintain that one does not know to what extent the Russian nuclear arsenal plays a role, similar to the uncertainty about the effectiveness of nuclear deterrence in general.Maybe the West has been prudent for other reasons, more in particular out of fear of a (conventional) world war, regardless of nuclear weapons (although it is admittedly very difficult to separate them out).In other words, if Russia had not possessed nuclear weapons, the West may have behaved in a similar prudent way.If that is the case, one could conclude -like John Mueller (1988) -that nuclear weapons are more or less irrelevant, and that nuclear deterrence is not a significant factor.

NATO's nuclear deterrent
A similar logic applies vis-à vis the Western nuclear deterrent.The French Minister of Foreign Affairs Jean-Yves Le Drian reminded Putin in the beginning of the war that NATO is a nuclear alliance too.Nuclear deterrence proponents claim that Russia limits itself to attacking (non-nuclear) Ukraine and does not seem to have any plans to attack NATO, even though NATO member states provide Ukraine with a lot of weapons (Meisel 2023).According to them, this shows that nuclear deterrence works.
In parallel with the reasoning in the previous section, critics use the following two arguments.First, it is unclear why Russia has not attacked NATO countries.Maybe Russia is only concerned about Ukraine.If that is the case, as some analysts claim (Mearsheimer 2014;Sauer 2017), the Western nuclear weapons are more or less irrelevant as Ukraine does not belong to NATO, even if membership (without setting a date) had been promised in 2008.Russia may also be deterred by NATO in general, not only by NATO's nuclear weapons.In other words, even if NATO was a non-nuclear alliance, Russia may not have dared to attack NATO member states.Again, we simply do not know, and we should not pretend that we do.
Secondly, it remains to be seen to what extent Russia will be deterred to use one or more tactical nuclear weapons in Ukraine, a move that may (or may not) end up in a nuclear war between the East and West.According to many nuclear experts, sometimes referring to the Russian doctrine of escalate-to-deescalate (Sokov 2022), the scenario that Russia uses a tactical nuclear weapon in Ukraine is not unrealistic, especially in case Russia is pushed out of Ukraine (Adamsky 2023;Bunn 2023;Giovannini 2022;Lieber and Press 2023;Ryan 2023;Sauer 2023;Ven Bruusgaard 2023).The goal is not so much of making a difference on the battlefield, but to create a psychological shock-effect in Ukraine and even more the West, comparable to the use of nuclear weapons in Hiroshima and Nagasaki.This in itself would not undermine NATO's nuclear deterrent as Ukraine is (still) not a NATO member state, but the escalatory moves that may follow may lead to a nuclear war between Russia and NATO.In that case, both NATO's and Russia's nuclear deterrent would have failed.Lieber and Press (2023, 54) point out: Those who downplay Russia's nuclear options misunderstand the logic of coercive escalation.Russia's goal would not be to rectify conventional military imbalance but to demonstrate in a shocking fashion that the war is spinning out of control and must be ended immediately.The aim would be to raise the prospect of a wider nuclear war and convince people and their leaders in the West that given what is at stake for Russian leaders, Moscow will keep inflicting pain to forestall defeat.If Russian escalation triggered a largescale conventional NATO attack on Russia's forces in Ukraine, as many analysts expect it would, Moscow could just use nuclear weapons again.With respect to the first step also President Biden has stated that Russia could use a tactical nuclear weapon in Ukraine (Talmazan 2023).Former US general Kevin Ryan (2023) even predicts that Russia will use a tactical nuclear weapon in Ukraine: " . . ., during the past 12 months, Putin has laid the groundwork for using a tactical nuclear weapon in Ukraine.He has removed domestic and operational barriers to doing so and has created justifications, fabricated and real, so that his people support him.In speeches and interviews, he has made the case that Russia is under existential attack -a situation that warrants the use of nuclear weapons".President Biden has already implicitly made clear and President Macron has explicitly said (Caulcutt 2022;Stein 2023, 45) that in case a Russian tactical nuclear weapon is used in Ukraine, NATO will not react with nuclear weapons.The latter shows their prudence, but at the same time may encourage Putin to execute his threat (Sanger and Tankersley 2022).
If Russia uses a tactical nuclear weapon in Ukraine, NATO may react with a large-scale conventional attack against Russian troops and assets in Ukraine.The latter may escalate to the nuclear level in which case Russian and the Western nuclear deterrent had failed (Gower and Weber 2022;Shapiro 2022).President Biden -in the hope to prevent such an event occurring in the first place -also made this link: "I don't think there is any such thing as the ability to easily [use] a tactical nuclear weapon and not end up with Armageddon" (quoted by Pifer 2022).Even deterrence by denial advocates Keir Lieber and Daryl Press understand that nuclear weapons use by the West is extremely dangerous: "Engaging in an escalatory tit-for-tat would be foolish because Putin has much more at stake -his regime's survival, and perhaps even his life -than the West does" (Atlantic Council 2022).Former Pentagon official William Alberque, senior researcher at IISS, says that the question of how to respond to non-strategic nuclear use by Russia in Ukraine "keeps U.S. planners awake all night" (Trevelyan 2024).In February 2024, the Financial Times revealed leaked files showing Russia's low bar for use of tactical nuclear weapons, a policy that is apparently already in place since 2008 (Seddon and Cook 2024).
Other observers disagree with this assessment.Gideon Rose (2022) believes that Putin is more rational and "knows that extraordinary retaliation and universal opprobrium would follow . . .not to mention the fact that the radioactive fallout from such use might easily blow back into Russia itself".Still others think about the reputation of the United States in the longer term with respect to nuclear deterrence (Bollfrass and Herzog 2022, 11;Rachman 2022a).Former US DOD appointee Walter Slocombe warns: "The absence of a US nuclear response would gravely weaken the credibility among both friends and adversaries of the entire strategy of deterring nuclear attack through the prospect of US nuclear retaliation.This, in turn, would make a bigger war more likely" (Atlantic Council 2022).Some therefore recommend to threaten early nuclear use by the West, more in particular by using US tactical nuclear weapons stationed in Europe (Bowen 2022).This debate points to the classic credibility problem of nuclear deterrence and more in particular extended nuclear deterrence, whereby the United States aims to defend its allies with a nuclear umbrella (Sauer 2022).

The absence of Ukraine's nuclear deterrent
Some observers point out that if Ukraine had kept the Soviet nuclear weapons that were stationed on Ukraine's territory in the beginning of the 1990s, which it did not, this war would not have happened (Umland 2022).This argument is impossible to check (as it is a counterfactual), but is in all likelihood incorrect (Larison 2023).First of all, Ukraine was not in a position to use the remaining Soviet nuclear weapons on its territory -under Russian command and control -at that time, and certainly not for a long time as components of nuclear weapons (such as tritium) had to be replaced on a regular basis.Ukraine did not possess these components.Secondly, in case that Ukraine had not agreed to give the weapons back to Russia, the odds are that Russia would have already invaded Ukraine in the 1990s (Evangelista 2023, 39-40).
To conclude, the war in Ukraine does not teach us much about nuclear deterrence theory (Gibbons and Herzog 2023, 9;Ingram 2022), although both camps -advocates and opponents -claim that it does.For instance, Mark Bell (2024, 4) posits that "what we are observing [in the war in Ukraine] is run-of-the-mill, straightforward, basic, plainvanilla deterrence".As a result, unsurprisingly, many Polish politicians and commentators are now in favour of becoming a host nation for US tactical nuclear weapons (Borger 2022), and two former generals in Europe recommend the EU to get a nuclear deterrent of its own because of this war (Lanxade et al. 2023).Opponents of nuclear weapons in contrast conclude that the war in Ukraine shows again that nuclear deterrence does not work (Johnson 2022).Unfortunately (or fortunately), this war (up to now) does not help to approve or disapprove nuclear deterrence theory.

Nuclear Responsibility
A second theory that is related but different from nuclear deterrence theory states that nuclear-armed states are (Waltz, 1981; for a different view, see Beardsley and Asal 2009;Bell 2021) or should be (Brixey-Williams and Wheeler 2020) "responsible" states.This theory states that nuclear weapons are defensive weapons, meant to deter, not to be used.Nuclear weapons are political instead of military weapons.The theory also implies that nuclear-armed states will not start major conventional wars, especially not expansionist wars, as this would contravene art.2 of the UN Charter and would be seen as "irresponsible".
The difference with nuclear deterrence theory is that nuclear deterrence logically implies the possibility of and maybe even the desirability of nuclear weapons use in case nuclear deterrence fails.If not, the threat is not credible.The nuclear responsibility theory in contrast emphasizes that because of the immense destructive capacity, these weapons inject a dose of prudence in geopolitics both on the side of the one that is deterred (which is emphasized by nuclear deterrence theory) and on the side of the possessor of nuclear weapons.The enemy is supposed to be deterred, and will not attack; at the same time, the possessor of these weapons of mass destruction is supposed to be self-deterred and to behave responsibly, both vis-à-vis nuclear and non-nuclear weapon states.That is also the reason why nuclear weapon states provide positive and negative security guarantees to non-nuclear weapon states.Based on this theory, one expects nuclear weapon states to behave responsibly, for instance by not starting expansionist wars and/or threatening or coercing other states, let alone explicitly threatening with or using nuclear weapons.
Critics claim that the theory of nuclear responsibility was already on weak grounds.Its mirror-image is the theory of nuclear opportunism that argues that nuclear-armed states may feel emboldened to take "irresponsible" decisions like attacking other states, thanks to their nuclear weapons (Bell 2021(Bell , 2024)).North Korea for instance has not been behaving very responsibly, even after having acquired nuclear weapons.
Proponents of the theory of nuclear responsibility argue that one should make a difference between "responsible" and "irresponsible" nuclear weapon states.Critics in contrast will refer to wars or attacks by (also "responsible") nuclear-armed states against non-nuclear weapon states, e.g. the United States against North Korea, Vietnam, Iraq, and Afghanistan, and Israel attacking Iraq and Syria.To the credit of the advocates of the theory of responsibility, one could argue that these wars were not expansionist wars in the sense of aiming to occupy parts of (or the whole) territory of the enemy.The use of explicit nuclear threats remained rather limited as well.And when push came to shove, presidents behaved prudently.When US general Douglas MacArthur insisted on using nuclear weapons in Korea, he was relieved from his duties by President Eisenhower.
The war in Ukraine, however, does not match with the nuclear responsibility theory (Arceneaux 2023).A nuclear-armed state -Russia, known as a "responsible" nucleararmed state -cowardly attacked a non-nuclear weapon state (Ukraine) with conventional weapons behind a wall of 6,000 nuclear weapons (Biswas 2023;Cocksworth 2022).Russia started a war by choice -provoked or unprovoked -that aimed to occupy and annex parts of the territory of Ukraine.These actions are exactly the opposite of what the nuclear responsibility theory predicts.
Right from the beginning of the invasion, President Putin also explicitly threatened to use nuclear weapons (see nuclear coercion; for a critical view, see Ingram 2022).Such statements cannot be categorized as responsible behaviour and does not match the nuclear responsibility theory.This theory has been proven wrong or at least severely undermined by this war.
Critics may argue that Russian nuclear weapons did not play a substantial role in the Russian decision to attack Ukraine.Even if Russia had not possessed nuclear weapons, it may have attacked Ukraine.That may or may not be true.That said, the odds are that the fact that Russia did possess nuclear weapons in contrast to Ukraine facilitated the Russian decision to attack (Futter 2023;McDermott, Pauly, and Slovic 2023).Russian nuclear weapons "potentially enabled Russia's invasion and conduct of the war in Ukraine", as Anya Fink (2023, 32) concludes.
Interestingly, as a reaction to these Russian nuclear threats, China and India made clear that they did not agree with Putin.Other political leaders -also from nuclear-armed states and nuclear alliances -warned that "any use of nuclear weapons is absolutely unacceptable", as NATO Secretary-General Jens Stoltenberg (2022) stated in the European Parliament.The G-20, including eight nuclear-armed states, agreed in Bali in November 2022 that nuclear use and threats of use are "inadmissible" (G-20 2022).Such declarations strengthen the nuclear taboo and the nuclear responsibility theory.At the same time, they undermine nuclear deterrence theory.
To conclude, the war in Ukraine is (again) a significant blow to the theory of nuclear responsibility.

Nuclear Coercion
Nuclear coercion -that is here used as a synonym for nuclear compellence (for a different view, see Schelling 1966) -means that nuclear-armed states are able to change the behaviour of other states -without having to use (nuclear) weapons -by demanding something that they are not willing to do and (implicitly or) explicitly threatening to use nuclear weapons in case the demand is not followed up.In comparison with nuclear deterrence theory, the nuclear coercer is behaving more actively than under nuclear deterrence that only aims to prevent an aggressive action by the enemy.The literature is divided on the effectiveness of nuclear coercion, but most observers seem to be rather critical vis-à-vis its effectiveness (Sechser and Fuhrmann 2017).
A distinction is made between Russian nuclear coercion vis-à-vis the West and vis-àvis Ukraine.

Russian Nuclear Coercion Against the West
Vis-à-vis the West, there are three episodes in the conflict that could be regarded as examples of nuclear coercion.Before and during the NATO Summit in Bucharest in 2008, Russia tried to prevent a decision by NATO to allow Ukraine membership.That was a clear demand.While there were no explicit nuclear threats, Russia made very clear that it was very much against Ukrainian membership, and that such a decision would yield negative consequences, including the possible annexation of the Crimea and parts of Eastern Ukraine.Nevertheless, the NATO Summit concluded that Georgia and Ukraine "will become member".The latter was a very disappointing outcome for Russia, and arguably the main grievance behind the ongoing war (Mearsheimer 2014;Sauer 2017).The fact that at the Summit no deadline was set did neither satisfy Ukraine nor Russia.Ukraine was not satisfied because of the absence of a deadline.Putin was angry because NATO had taken the decision to extend NATO further.He reacted a couple of months later by provoking Georgia into a war, and by attacking Ukraine in 2014 (when the EU tried to bring Ukraine into the Western orbit), for which he had already warned in 2008.In short, as Russia executed its threat, Russian (implicit) nuclear threat and coercion had failed.
The second episode contains a more explicit example of nuclear coercion, although it remains rather difficult to distinguish it from nuclear deterrence.Right after the start of the Russian invasion in February 2022, President Putin warned that any country standing in Russia's way would face "consequences such as they have never seen in their history", an explicit threat and a clear demand.He publicly asked the Russian military to increase the alert-levels, and he repeated similar threats during the war.A half year later, for instance, on 21 September 2022 when Russia lost annexed territory, President Putin stated: "If the territorial integrity of our nation is threatened, we will certainly use all the means that we have to defend Russia and our people.This is no bluff".One week later, on 30 September, he said: "We will defend our land with all our forces and resources, adding that the United States had created a precedent for nuclear use in Hiroshima and Nagasaki".On 16 June 2023, Putin stated again that the use of a tactical nuclear weapon is possible "if a threat is created to our territorial integrity, independence and sovereignty, the existence of the Russian state".Russian strategists, some of them known as having belonged to the moderate camp (like Dimitri Trenin), echoed these threats in articles in which they prescribed the use of nuclear weapons against "a bunch of targets in a number of countries in order to bring those who have lost their mind to reason" (Karaganov 2023; see also Trenin 2022; for a different view, see Adamishin et al., 2023).They proposed to use nuclear weapons pre-emptively against Western Europe.That kind of rhetoric is something that we have never seen, not even during the Cold War.In this regard, Adamsky (2023) points out that we can speak of "Russia's new nuclear normal".
Many Western analysts believe that this nuclear rhetoric is mainly used by the Kremlin and its local supporters for coercive reasons instead of effectively using nuclear weapons (Applebaum 2022;Giles 2022;T. Snyder 2023).They also remind us that the concept of coercion is only successful if the threat is not executed.They call these threats bluff (Oliker 2022).Horovitz and Wachs (2022, 2), for instance, state: "In this way, nuclear weapons are a tool of intimidation and of escalation management", but "the probability of an intentional use of nuclear weapons remains extremely low".Similarly, others -just like Thomas Schelling in the past -point out that for this reason it is useful for Putin to appear mad, which is different from being mad (Harford 2022).
However, not every expert is reassured (Colas 2023).Also Krepinevich (2022) observes that "leaders make some decisions that appear irrational when viewed from a strictly transactional perspective [such as the use of nuclear weapons] but less so when taking into account perceptions of honor and justice"."The difficult task is to separate risk manipulation from the actual possibility of use", Matthew Harries (RUSI) adds (Eyal and Harries 2022).He also refers to the weeks before the invasion in 2022, when most observers believed that Putin was bluffing, an assessment that later on appeared wrong.Similarly, Harries could have pointed to Putin's threat in 2008 with respect to Ukrainian NATO membership.Again, at that time Putin was not taken serious by the Western leaders, in particular by President Bush,Jr.Later on (in 2014), however, Putin did what he had threatened to do.It was no bluff.Russian coercion failed.
The concrete demands of the Russian government as part of its nuclear coercion effort, however, are not very clear.If Putin's goal was to prevent Western support to Ukraine in the form of arms deliveries, he clearly failed (Bruusgaard 2023;Futter 2023).Others believe that Russian nuclear coercion has worked as President Biden has been relatively prudent, also with respect to arms deliveries (Vershbow 2023).
The decision by Putin in March 2023 to install Russian tactical nuclear weapons in Belarus, that was executed in the summer of 2023, can be regarded as a third example of nuclear coercion.In this case, President Putin did make the explicit demand to the West to stop arming and supporting Ukraine (Osborn, 2023).This threat, however, has not stopped the West of further supporting Ukraine, including with more and bigger arms (such as promising F-16s).Again, Russian nuclear coercion failed.

Russian Nuclear Coercion Against Ukraine
The failure of Russian nuclear coercion vis-à-vis Ukraine is even more straightforward.Russia referred on different occasion to its nuclear arsenal, at least implicitly and sometimes explicitly threatening the use of nuclear weapons, in all likelihood in Ukraine.The concrete Russian demand vis-à-vis Ukraine was to agree with the Russian war objectives, including the annexation of the Crimea and the Donbas.It did not work.Ukraine was and still is not deterred by the Russian nuclear threats.Ukraine fights back.Here again, the use of nuclear weapons in the form of coercion failed (Arndt, Horovitz, and Onderco 2023;Futter 2023;Thakur 2022).
To conclude, the empirical case of the war in Ukraine supports the literature on the ineffectiveness of nuclear coercion (Dreuzy and Gilli 2022).It is not easy to make nuclear coercion work.

Conclusion
The elephant in the room in the war in Ukraine are Russia's nuclear weapons.For the first time since very long, there is a possibility that nuclear weapons will again be used in an authorized way.This paper wanted to answer the question: what has been the impact of nuclear weapons in the war in Ukraine and what does that tell us about the usefulness of nuclear weapons in general?
Based on the analysis above, we conclude the following: first, nuclear-armed states do not always behave responsible in contrast to what the nuclear responsibility theory claims.Russia cowardly attacked Ukraine, a non-nuclear weapon state, behind a wall of 6,000 nuclear weapons.While the theory cannot be completely refuted on the basis of one case, it fits the critical view that nuclear-armed states on average do not behave more responsible than non-nuclear-armed states.Secondly, our analysis confirms the literature that states that nuclear coercion is very difficult.The war in Ukraine shows that nuclear weapons cannot easily be used to coerce non-nuclear weapon states.Thirdly, and lastly, the analysis above leads to less clear cut conclusions with respect to the viability of nuclear deterrence.As others have stated before (Wilson 2013), it is very difficult to conclude whether and to what extent it works or not.That applies also to the war in Ukraine.
All in all, the analysis points out a bleak picture with respect to the usefulness of the nonuse of nuclear weapons.Apart from deterring an attack against the vital interests of a state, nuclear weapons do not seem to provide many benefits.And even with respect to deterring an attack against the vital interests of a state, it is unclear to what extent nuclear deterrence works.It is therefore not surprising that former UN Deputy Secretary General Ramesh Thakur (2022) draws as a preliminary conclusion from this war that nuclear weapons show "their near complete lack of utility".At the same time, while the benefits are unclear, there are serious -potentially catastrophic -risks involved with nuclear deterrence.As Krepinevich (2022) warns: "History and the growing understanding of how the human mind works suggests that leaders should not assume that deterrence will be robust and the taboo against atomic weapons will prevent their use".Once they are used, the question is only whether it will be a minor or a major catastrophe, killing tens of thousands or tens of millions of people.Matthew Evangelista draws the following observation from the war in Ukraine: "one consequence of the war might be that advocates of nuclear weapons scale back their claims and ambitions" (2023,12).This conclusion, which corresponds to this analysis, seems to stand in contrast to the growing popularity of nuclear weapons, at least in Europe, as a result of the war (Onderco, Smetana, and Etienne 2023).One wonders to what extent the general public makes a rigorous cost-benefit calculus based on expertise or bases its opinion on more simple clues (including emotions).
Future research could further broaden the scope of the analysis by looking to the implications with respect to nuclear proliferation, nuclear arms control and disarmament.A preliminary answer may be that the war in Ukraine may not have large-scale repercussions with respect to nuclear proliferation (Knopf 2022;Bell 2024; for a critical view, see; Umland 2022; Schepers 2022).That said, the 10 th NPT Review Conference failed because the consensus document was blocked by Russia because of language related to the war.With respect to nuclear arms control, it is already clear that the war has made arms control (even) more difficult.New START has been suspended and will in all likelihood not be resurrected.Russia also revoked its ratification of the CTBT in the Autumn of 2023.Worse, the odds are that from 2026 (if not before) there will not be any bilateral nuclear arms control treaty left.
The jury on the repercussions with respect to nuclear disarmament is still out.The chances are high that there will be more obstacles on the road to nuclear disarmament as a result of this war; on the other hand, the war and the perceived dangers related to the possible use of nuclear weapons could also be a trigger to take the threat of nuclear weapons more serious and to work on nuclear disarmament (Biswas 2023;Gibbons and Herzog 2023;Wolfsthal 2022).

Disclosure Statement
No potential conflict of interest was reported by the author(s).

Notes on Contributor
Tom Sauer is Professor International Politics in the Department of Politics at the Universiteit Antwerpen, Belgium.He has published numerous academic articles as well as ten books (monographies or co-edited volumes).His latest book is titled Alliances in Asia and Europe (Routledge, 2024), and is co-edited with Elena Atanassova-Cornelis and Yoichiro Sato.