For decades after Hiroshima and Nagasaki, the very notion of using nuclear weapons was considered unthinkable. A powerful nuclear taboo took hold – an informal global norm against ever unleashing such devastation again[1]. Yet today, that long-held restraint shows signs of fraying. In military circles and halls of power, discussions of “limited” or tactical nuclear strikes are resurfacing. World leaders openly threaten their potential use, and nuclear-armed states are modernising arsenals to include smaller, “more usable” warheads[2][3]. This raises urgent questions: Why are tactical nuclear weapons becoming thinkable again, and what might it mean for global security? In this comprehensive look, we examine the history of nuclear weapon use – especially tactical weapons – and compare past taboos to modern-day thinking. We explore how the United States, Russia, China, and North Korea each view tactical nukes, what they say versus what they do, and how these weapons serve both on the battlefield and as political tools. Finally, we consider whether threatening or using a tactical nuclear bomb would make an enemy back down – or trigger even greater catastrophe.

The Nuclear Taboo: From 1945 to Today

When the United States dropped atomic bombs on Hiroshima and Nagasaki in 1945, the world witnessed horrors beyond imagining. Entire cities were obliterated; over 200,000 lives were lost, with survivors suffering radiation sickness and generational injuries. In the aftermath, an unspoken nuclear taboo emerged – a widespread belief that nuclear weapons must never be used again[4]. This norm has held firm for 77 years: despite countless wars and close calls during the Cold War, no country has fired a nuclear weapon in anger since 1945[5]. Nuclear-armed states instead embraced deterrence, threatening nuclear retaliation to prevent war, but stopping short of crossing the line into actual use[6].

This tradition of non-use is often credited with preventing full-scale war between superpowers. The strategy of Mutual Assured Destruction (MAD) – the guarantee that any nuclear attack would invite an equally devastating response – kept the United States and Soviet Union in check during the Cold War. Even as both sides amassed tens of thousands of warheads, they treated nuclear weapons as last-resort deterrents, not normal battlefield tools. A U.S. presidential advisor famously called nuclear war unwinnable, saying “the survivors would envy the dead.” World leaders on all sides largely agreed that to initiate nuclear use would be to sign humanity’s death warrant.

Yet the nuclear taboo has been under gradual erosion. In recent years, great-power conflicts and nuclear rhetoric have shaken the norm. Russia’s invasion of Ukraine in 2022, for example, brought nuclear threats back into headlines. President Vladimir Putin pointedly raised Russia’s nuclear alert status and warned he would use “all means” to defend Russia[7]. Putin’s brazen nuclear sabre-rattling – including veiled hints at using “so-called tactical (or ‘nonstrategic’) nuclear weapons” if NATO directly intervened[8] – has alarmed the world and undercut the long-held taboo. As one analysis notes, such rhetoric “can lead to a normalising effect, where the use of [nuclear] weapons becomes more thinkable in the minds of decision-makers.” If the norm against nuclear use weakens further, leaders may start to believe they can get away with limited nuclear strikes[9]. This disturbing trend has prompted experts and peace advocates to warn that the “unthinkable” is becoming dangerously thinkable again[10].

What Are Tactical Nuclear Weapons?

To understand this shift, we must clarify what tactical nuclear weapons are. Sometimes called “non-strategic” nuclear weapons, tactical nukes are generally lower-yield warheads and delivery systems intended for battlefield or limited use – as opposed to the city-annihilating strategic nuclear weapons on intercontinental missiles and long-range bombers. In practice, the distinction is blurry: even a “small” nuclear blast is enormously destructive. Most modern nuclear warheads have variable yields, or “dial-a-yield” settings, that can range from fractions of a kiloton up to hundreds of kilotons[11]. (For context, the Hiroshima bomb was about 15 kilotons[12].) A tactical warhead might be in the single-digit kiloton range – still enough to flatten several city blocks or devastate a military formation.

Tactical nuclear weapons come in many forms. During the Cold War, the U.S. and Soviet Union deployed nuclear artillery shells, land mines, depth charges, and short-range missiles. Today, Russia’s Iskander-M mobile ballistic missile (range ~500 km) can carry a nuclear warhead and is considered a key tactical system[13]. The United States, for its part, maintains about 100 B61 nuclear gravity bombs stationed in Europe[14] – these are also low-yield weapons deliverable by fighter jets. Other nuclear-armed states like Pakistan have developed short-range missiles explicitly for battlefield nuclear use as well. The motive for such weapons is clear: by making nuclear warheads smaller and more precise, military planners hoped their use might become more conceivable and controllable[15]. A retired U.S. defence secretary summed it up bluntly: “I do not think there is any such thing as a ‘tactical’ nuclear weapon. Any nuclear weapon used any time is a strategic game changer.”[16] In other words, even limited nuclear use would shatter the post-1945 tradition and fundamentally change a conflict’s trajectory.

Russia’s Iskander short-range ballistic missile system, shown here, can carry either conventional or nuclear warheads[17]. Such dual-capable missiles blur the line between conventional warfare and nuclear warfare on the battlefield.

Why “tactical” nukes at all? Proponents argue they fill a gap between conventional force and all-out strategic nuclear war. Military strategists feared that if their only nuclear option was to obliterate cities, the threat might lack credibility – it would be too self-destructive to carry out. Smaller nukes, the thinking goes, are “more usable, and thus more effective as a deterrent” because an enemy might believe you would actually fire one[18]. This paradox lies at the heart of today’s debate: making nuclear weapons appear more usable might strengthen deterrence, but it also makes it easier to imagine pulling the trigger[19]. By lowering the threshold for nuclear use, tactical arms risk turning nuclear war into a sliding scale rather than an absolute taboo. And once the nuclear threshold is crossed, nobody can be certain it would stay limited – the escalation risks are terrifyingly real[20].

United States: Official Restraint, New Tactical Options

The United States publicly casts its nuclear weapons as purely defensive – the “last resort” to protect itself and its allies in extreme circumstances[21]. U.S. leaders often emphasise that the bar for any nuclear use is extraordinarily high. In fact, Washington has repeatedly considered but ultimately rejected adopting a formal “no first use” pledge, arguing that fully renouncing first use would pose “unacceptable risk” given modern threats[22]. Instead, the 2022 U.S. Nuclear Posture Review reaffirmed that America would only consider nuclear strikes in extreme situations to defend vital interests, and maintains a “very high bar” for employment[23]. In practice, the U.S. doctrine still allows first use of nuclear weapons if necessary – for example, to deter or respond to non-nuclear attacks that cause massive devastation[24]. The message is intentionally ambiguous: keep adversaries guessing, so they fear that any major aggression could potentially trigger a U.S. nuclear response[25].

At the same time, U.S. policymakers insist they are not lowering the threshold for nuclear war. This was evident in how they handle tactical nuclear capabilities. After the Cold War, the U.S. retired most of its shorter-range nuclear arms. In 1991, for instance, President George H.W. Bush unilaterally withdrew all American nuclear artillery shells and tactical missiles from Europe, aiming to set an example for de-escalation. For years, the only U.S. “tactical” nukes were gravity bombs like the B61, which remain forward-deployed in NATO countries as a deterrent symbol. However, Russia’s large arsenal of tactical warheads and its more aggressive posture in recent decades have spurred the U.S. to develop new low-yield nuclear options. In 2018, the Trump Administration’s Nuclear Posture Review warned that Moscow might perceive a gap in U.S. capabilities – that Russia might use a small nuke in a regional war, thinking Washington would balk at retaliating with high-yield strategic weapons[26]. To “counter any mistaken perception” of a gap, the U.S. quickly fielded a new W76-2 low-yield warhead for submarine-launched ballistic missiles[27]. This warhead, only about 5 kilotons in explosive power (roughly one-third of Hiroshima’s yield), was first deployed on a Trident submarine in 2019[28].

Officials described the W76-2 as a “usable” nuclear weapon meant to “respond in kind to a low-yield nuclear attack”[29]. In other words, if an adversary detonated a small nuke on the battlefield, the U.S. wanted the option to fire a small nuclear counterstrike rather than immediately jump to city-busting bombs or do nothing. Advocates argued this flexibility actually strengthens deterrence by convincing rivals that even limited nuclear aggression will be met with a proportional nuclear response[30]. However, critics note a certain doublethink: the U.S. insists its new low-yield nukes raise the threshold and are “very stabilising”[31], even as it accuses Russian low-yield weapons of lowering the threshold. Washington assures that these warheads “do not enable nuclear war-fighting”[32] – they are meant to prevent war, not wage it. Nonetheless, by putting a more “usable” nuke to sea, the U.S. has inched closer to the line it swore never to cross. It’s telling that former U.S. Défense Secretary Jim Mattis cautioned in 2018, “I do not think there is any such thing as a tactical nuclear weapon. Any nuclear weapon used any time is a strategic game changer.”[33] This reflects an enduring institutional reluctance in the U.S. military to ever employ nuclear arms, despite developing a few tailored tools for worst-case scenarios.

As of today, the United States continues to modernise its nuclear arsenal for deterrence, but with an official policy of restraint. The Biden Administration’s 2022 review actually cancelled a planned nuclear sea-launched cruise missile, judging it redundant now that the sub-based W76-2 exists[34]. The U.S. also retired its last megaton-class gravity bomb (the B83), focusing instead on precision B61 bombs and advanced stealth delivery systems. Publicly, American leaders condemn talk of nuclear use – especially Russia’s nuclear threats – as “irresponsible” and vow that any nuclear attack by an adversary will meet a severe response[35][36]. The U.S. has even signalled directly to North Korea that “there is no scenario in which the Kim regime could employ nuclear weapons and survive.”[37] In short, America says nuclear weapons are only to deter aggression and never to be used lightly – yet it is also quietly ensuring it has a few lower-yield options on hand, just in case. This hedging illustrates the tension many nuclear states face: maintaining the taboo in rhetoric but preparing for the possibility that it might break in reality.

Russia: Sabre-Rattling and “Escalate to De-Escalate”

If the United States views tactical nuclear weapons with ambivalence, Russia embraces them as a core element of its defence strategy. Russia inherited the Soviet Union’s vast nuclear arsenal and today possesses the world’s largest stockpile of nuclear warheads – roughly 4,500 in total, of which about 2,000 are tactical warheads kept in reserve[38]. These range from nuclear bombs and cruise missiles to short-range battlefield weapons. In sheer numbers, Moscow enjoys a huge numerical superiority in non-strategic nukes over the West; U.S. officials estimate Russia has around 2,000 tactical warheads, versus roughly 200 for the United States (about half of which are deployed in Europe)[39]. This imbalance stems from Cold War history and Russia’s security outlook. After the Soviet collapse, Russia’s conventional military was relatively weak through the 1990s, so it leaned more heavily on nuclear forces as the ultimate guarantor of its security. Tactical nukes were a way to offset NATO’s superior conventional technology – a last-resort equaliser if Russia ever faced overwhelming defeat in a conventional war.

Officially, Russia’s published nuclear doctrine sounds fairly restrictive. President Putin approved an updated nuclear deterrence policy in 2020 that allows nuclear use in four scenarios: (1) in response to a nuclear or other WMD attack on Russia or its allies, (2) in response to conventional aggression that threatens “the very existence of the state,” (3) upon reliable warning of ballistic missiles heading for Russia, or (4) if an enemy attack on critical infrastructure would cripple Russia’s nuclear forces[40]. Two of those criteria – the missile launch warning and protecting nuclear infrastructure – were new additions, reflecting Russian anxiety about sudden decapitation strikes. Importantly, the doctrine casts Russia’s nuclear policy as “purely defensive…to prevent aggression”[41]. It does not openly endorse using nuclear weapons to seize territory or “win” a war it started. In fact, Kremlin spokesman Dmitry Peskov asserted in 2020 that “Russia can never and will never initiate the use of nuclear weapons.”[42] On paper then, Russia claims it would fire nukes only in extreme defensive scenarios, much like the U.S. stance.

Television in Seoul showing a North Korean missile launch (Yonhap News, 2022). Russia’s frequent nuclear threats during the Ukraine war have similarly put neighbouring countries on edge[43].

However, Moscow’s actions and rhetoric tell a more aggressive story. Putin and other Russian officials have repeatedly brandished the threat of nuclear strikes to coerce adversaries. During the 2014 Crimea crisis, Putin pointedly reminded the world of Russia’s nuclear arsenal, and Russian media even mused about targeting Western capitals. In 2015, Moscow warned it could target NATO warships with nuclear weapons if they joined a U.S. missile defence effort[44]. And since launching the Ukraine war in 2022, Putin has continually hinted that if Russia’s back is against the wall, he might resort to a nuclear option. He raised Russia’s nuclear alert level early in the conflict[45], a signal clearly aimed at deterring the U.S. or NATO from direct intervention. The gambit worked to an extent – Western leaders, fearful of World War III, limited their support to arms shipments and ruled out any “no-fly zone” confrontation with Russian forces[46]. In effect, Putin used nuclear deterrence not just to protect Russia, but to facilitate conventional aggression against Ukraine[47]. This inversion of deterrence – using nukes as cover for offensive war – deeply worries security analysts. It chips away at the notion that nuclear weapons are solely peace-keepers; instead, they became tools of coercion to “have his way in Ukraine” as one scholar put it[48].

Western experts often describe Russia’s approach as “escalate to de-escalate.” In a scenario where Russia is facing defeat in a regional war (even one it started), it might escalate by firing a tactical nuclear strike, hoping to shock the adversary into backing down on terms favourable to Moscow[49][50]. This could mean, for example, nuking a military target or even a sparsely populated area as a demonstration, basically saying: “We’re willing to go nuclear – are you sure you want to continue the fight?” The logic is brutally cynical but not implausible. There is evidence that Russia has war-gamed early nuclear use in a European conflict during military exercises[51]. And Putin’s own words align with the concept: he stated in 2018 that if a fight is inevitable, “we will act first”, and that a world without Russia “would not be worth living” – implying he might use nukes if Russia’s existence were at stake. The 2020 doctrine even contains phrasing that believers in “escalate to de-escalate” seize upon: it says Russia’s deterrence policy aims to “prevent escalation of military actions and terminate them on conditions acceptable to Russia.”[52] To more hawkish Russian strategists, that sounds like an endorsement of ending a war with a limited nuclear strike.

In practice, we have fortunately not seen any nuclear use by Russia – yet. But the taboo is eroding in their discourse. Putin’s government has normalized discussion of nuclear weapons as just another tool, to the point that some Russians speak casually about striking European capitals or using “small nuclear” bombs in Ukraine. Russia’s state media often amplifies nuclear threats. And concrete steps reinforce the menace: in 2023, Russia began deploying tactical nuclear weapons to Belarus, moving warheads closer to NATO’s borders[53]. The Russian defence minister, Sergei Shoigu, announced that Belarusian aircraft and Iskander missile units were being made nuclear-capable[54]. This is Russia’s first placement of nuclear arms outside its territory since the Soviet era[55], and it was justified as a response to “Western aggression.” Meanwhile, the Kremlin claims it is the threatened party. Putin portrays the Ukraine war as a fight for Russia’s survival against an expanding NATO, thereby rationalising that “all means” – including nuclear – remain on the table[56]. The result is a dangerous ambiguity: Russia says nukes are only for existential defence, but it does brandish them to intimidate and possibly to stave off defeat in conflicts it initiated. This gap between words and deeds makes the global security environment precarious. As NATO officials have noted, if Moscow ever crossed the nuclear threshold, even with a “limited” strike, it would fundamentally change the nature of war in Europe – and the world – in an instant.

China: No First Use Policy Amid a Modernising Arsenal

China’s nuclear posture stands apart from the U.S. and Russia in key ways. Officially, China has maintained a strict No First Use (NFU) policy since it first developed nuclear weapons. From the moment of its first atomic test in 1964, Beijing declared it “will never be the first to use a nuclear weapon” and would only employ nukes in retaliation for a nuclear attack on China[57]. This pledge, reiterated many times over the decades, positions China as a reluctant nuclear power – one that sees these weapons purely as a deterrent against nuclear blackmail, not as tools for war-fighting or coercion. Chinese officials often describe their country’s nuclear strategy as a minimal, self-defensive deterrent. China’s arsenal was for many years the smallest of the major powers, and it kept most warheads stored separately from missiles (not mated for quick launch), reflecting a posture of low alert. The core of China’s doctrine is to ensure it can survive an enemy nuclear strike and retaliate – a concept known as “assured retaliation”[58]. As long as China can inflict unacceptable damage on any aggressor, it believes it can deter anyone from using nuclear weapons against it in the first place.

True to that philosophy, China historically deployed only a few hundred nuclear warheads, just enough to threaten retaliation against enemy cities. It did not field a variety of tactical nuclear weapons like the U.S. and USSR did. In fact, for decades China lacked the kind of short-range, low-yield nuclear options that characterised U.S. and Russian arsenals. Beijing seemed content with a lean arsenal focused on hitting key strategic targets (like cities or military bases) in response to a nuclear attack. China also eschewed nuclear sabre-rattling. Unlike Russia or North Korea, Chinese leaders rarely brandish nuclear threats in crises. Even during tensions over Taiwan or border clashes with India, China’s statements have generally not invoked its nuclear weapons. This restraint underscores a continued commitment to the nuclear taboo – at least in peacetime diplomacy.

That said, China is now in the midst of a significant nuclear modernisation and expansion. Recent U.S. intelligence reports and satellite imagery indicate China may be increasing its arsenal to 500 or more warheads in the next few years[59], building new missile silos in its western deserts and deploying additional mobile ICBMs. It has also tested advanced delivery systems like hypersonic glide vehicles. All three legs of China’s nuclear “triad” – land-based missiles, submarine-launched missiles, and air-launched weapons – are being updated or expanded[60]. What explains this buildup? Chinese officials still insist they will never strike first[61], but they see a need to bolster their deterrent as other powers evolve. For example, the U.S. has been developing missile defence systems and precision conventional weapons that could threaten China’s nuclear forces. To maintain a credible second-strike, China may feel it must enlarge and diversify its arsenal (so it cannot be wiped out pre-emptively)[62]. Some Chinese strategists also observe Russia and the U.S. integrating “limited” nuclear options and wonder if China should have flexible deterrence options too. However, there is no public evidence that China is developing dedicated tactical nuclear warheads or adopting a war-fighting doctrine. Its new nuclear-capable missiles (like the DF-26 intermediate-range missile, sometimes dubbed the “Guam killer”) could theoretically be used in a regional conflict, but China has not signalled any intent to use nuclear weapons for battlefield advantage in a conventional war.

The contrast between words and deeds is less stark for China than for other nuclear powers, but some ambiguity is creeping in. Beijing’s staunch NFU pledge has been questioned by outsiders who note that China’s official statements sometimes include caveats (for instance, whether an NFU would hold if the regime’s survival were at stake due to conventional attacks). Chinese officials maintain that their NFU is absolute, and there is no reason to doubt it – unless China itself were nuked first[63]. Still, as China’s arsenal grows and it becomes a peer nuclear competitor to the U.S. and Russia, one wonders if its nuclear philosophy could evolve. At present, China says it rejects the idea of tactical nuclear war and appears to practice what it preaches: no provocative nuclear posturing, just a steady enhancement of its deterrent to ensure it cannot be bullied. Its focus remains on political deterrence (preventing war, especially nuclear war) rather than seeking any utility from nuclear weapons on the battlefield. In summary, China stands by a policy of not using nuclear weapons first and portrays itself as a responsible nuclear power. Yet its rapid arsenal expansion hints that it is preparing for a more uncertain future – one in which having a larger and more sophisticated nuclear force might dissuade multiple rivals and give Beijing greater security in a highly competitive environment[64].

North Korea: From Deterrence to Brinkmanship

North Korea provides a starkly different case – a small, isolated state that sees nuclear weapons as its ultimate survival guarantee and, increasingly, as a versatile tool for brinkmanship. Pyongyang’s regime, led by Kim Jong-un, has rapidly advanced its nuclear arsenal in defiance of international sanctions and pressure. While the exact numbers are uncertain, North Korea has likely assembled a few dozen nuclear warheads and is producing more fissile material each year[65]. What makes North Korea particularly worrisome is how openly it threatens to use those weapons, even pre-emptively. Unlike the cautious, coded language of other nuclear states, North Korea’s rhetoric often leaves little to the imagination. Kim Jong-un has declared that his country’s nuclear status is “irreversible” and there will “never be any declaration of giving up our nukes”[66]. In 2022, North Korea’s Supreme People’s Assembly codified a new nuclear law that goes far beyond mere deterrence. This law formalised Pyongyang’s nuclear use doctrine and even authorised automatic nuclear strikes if Kim’s leadership is endangered – for instance, if an enemy decapitation strike were to kill or incapacitate him[67]. Essentially, North Korea predelegated launch authority to ensure that trying to eliminate Kim would trigger nuclear retaliation even if the leadership is gone. This hair-raising posture is meant to deter any US–South Korean plans of a precision strike to end the regime.

North Korea’s stated doctrine now includes two missions for its nuclear forces: (1) deterrence of outside attack, and (2) warfighting to repel aggression if deterrence fails[68]. Kim Jong-un has explicitly said nuclear weapons could be used to “repulse hostile forces’ aggression and achieve victory” should war break out[69]. The new law lists ambiguous scenarios for nuclear use, such as if a “fatal military attack against important strategic objects” appears imminent, or when necessary to “take the initiative in war”[70]. These broad conditions essentially give Kim wide latitude to launch a nuclear first strike even against a non-nuclear adversary, if he judges it necessary. In plainer terms: North Korea does not subscribe to No First Use at all – it has openly stated it might fire nuclear weapons first in a conflict, including to pre-empt an anticipated invasion or to break enemy forces on the battlefield[71]. This is a dramatic evolution from the past, when Pyongyang at least framed its nukes as purely defensive. Now, their doctrine edges toward nuclear warfighting, at least at the tactical level, against superior conventional forces.

The regime’s actions back up this posture. North Korea has tested a wide range of missiles, from ICBMs capable of striking the U.S. mainland to solid-fuelled short-range ballistic missiles designed to evade regional missile defences[72]. In recent years, it has placed special emphasis on developing “tactical” nuclear weapons and delivery systems. Kim announced in January 2021 that the country had achieved the ability to “miniaturize, lighten and standardize nuclear weapons and to make them tactical ones.”[73] By 2023, North Korea even unveiled a new, smaller nuclear warhead (dubbed the Hwasan-31 by analysts) and claimed it could be mounted on at least eight different platforms – including short-range missiles, cruise missiles, and even an underwater drone[74]. Kim vowed to “mass produce” tactical nuclear weapons for frontline units[75]. All this suggests North Korea aims to arm some of its short-range missiles (which threaten South Korea and U.S. bases in Asia) with nuclear warheads for actual battlefield use. If war erupted on the Korean Peninsula, Pyongyang might, for example, detonate a nuclear bomb over the ocean or on a South Korean troop concentration as a shock tactic. The regime likely calculates that such a move could paralyse the U.S.-South Korean alliance with fear and force a ceasefire on North Korean terms.

Of course, using a nuclear weapon would also invite devastating retaliation. U.S. and South Korean officials have sternly warned Kim that any nuclear attack would be suicidal for his regime[76]. The U.S. maintains overwhelming nuclear superiority and has extended its “nuclear umbrella” to protect South Korea and Japan. This raises the stakes of any North Korean nuclear strike: it could trigger a U.S. nuclear response or a massive conventional onslaught to eliminate the Pyongyang regime. Kim Jong-un is surely aware of this; thus, his nuclear threats serve a political purpose as much as a military one. By brandishing the possibility of unpredictable nuclear escalation, North Korea aims to deter any attempt at regime change or invasion. The mere existence of its nukes complicates every crisis, as Washington and Seoul must calculate the risk that pushing Kim too far could spark nuclear catastrophe. In that sense, North Korea uses the threat of tactical nuclear war to hold much stronger powers at bay. It’s a high-stakes gambit of brinkmanship: appear willing to go nuclear over even limited conflicts, so that opponents tread carefully.

In summary, North Korea openly says it might use nuclear weapons first, and it is doing everything it can to make that credible – testing missiles, building warheads, and enshrining launch authority in law. This aggressive posture marks the most direct assault on the nuclear taboo in the world today. Pyongyang’s leadership seems to believe that threatening a nuclear holocaust is a legitimate means to ensure their own survival. It is a sobering example of how deterrence can morph into coercion when a nuclear-armed state feels cornered.

Tactical Nukes: Battlefield Weapon or Political Lever?

Tactical nuclear weapons occupy a grim middle ground between conventional war and Armageddon. Military planners see potential battlefield uses: for example, a nuclear blast could wipe out a hardened command bunker, decimate an advancing armoured division, or obliterate an aircraft carrier strike group – targets that might be difficult to destroy with conventional arms. The psychological impact is even greater: a nuclear explosion, however small, could shock an enemy into paralysis or retreat out of sheer terror. This is the theory behind “escalate to de-escalate” – use a nuke to jolt the opponent into backing down[77][78]. In political terms, even a threat to use a tactical nuke can be a powerful lever. We’ve seen how Russia’s nuclear threats likely deterred NATO from intervening directly in Ukraine[79], and how North Korea’s weapons deter attacks on its regime. In crises, leaders may brandish tactical nukes as bargaining chips: “If you cross this red line, we’ll resort to the ultimate weapon.” The value of tactical nukes, then, is not just in their explosive force but in the fear they instil. They raise the stakes of any confrontation dramatically, which can either freeze a conflict or dangerously escalate it.

On the other hand, the idea of a “limited” nuclear war remains deeply controversial and arguably illusory. Once one nuclear weapon explodes in battle, all bets are off. The targeted side – if it has nuclear weapons – may feel compelled to retaliate with its own nukes, potentially leading to an escalating exchange. Even if the opponent lacks nukes (say, Ukraine facing a Russian strike), the shockwave of global outrage and pressure could pull other nuclear powers into the fray or at least trigger massive conventional retaliation against the user. Former U.S. defence secretary Mattis captured this uncertainty, saying “any nuclear weapon used any time is a strategic game changer.”[80] The bomb that was meant to stay tactical could have strategic consequences. For instance, if Russia used a “small” nuclear bomb in Ukraine, NATO might not respond with nuclear weapons (to avoid all-out war), but it would almost certainly respond in other severe ways – possibly massive cyber-attacks, conventional strikes on Russian forces, or draconian economic punishment. The conflict could spiral in unpredictable directions. Similarly, if Pakistan used a tactical nuke on an Indian tank column, India’s stated doctrine is to retaliate with overwhelming nuclear force, not to back down. In that scenario, a single battlefield nuke could trigger full-scale nuclear war in South Asia – a nightmare for the world.

History fortunately provides no real example (yet) of how an enemy reacts to a tactical nuclear strike, so we are left with theories and war games. Some war games have suggested that once the nuclear threshold is crossed, escalation might be difficult to control, as fear and anger take hold. Others argue that rational actors would seek to de-escalate after a limited nuclear use – essentially, they’d be so horrified that they would rush to negotiate peace. The truth may depend on context. If a nuclear weapon is used against a country that also has nuclear weapons, the pressure to retaliate in kind is enormous – a matter of credibility and national resolve. Conversely, against a non-nuclear opponent, the horror might force that opponent to the negotiating table or stiffen their resolve with international support. What’s clear is that the “nuclear taboo” – 77 years of non-use – has been a blessing to the world[81]. It has prevented us from finding out firsthand whether limited nuclear war can be contained. Once that taboo is broken, even by a tactical nuke, we will enter uncharted and perilous territory[82][83]. As one nuclear scholar noted, those on the receiving end of a nuclear blast “are not likely to ask whether it was tactical or strategic” – it’s an act of war unlike any other[84]. And Russian officials have warned they would view any nuclear attack as the start of an all-out war[85], implying there’s really no safe threshold.

From a political standpoint, even threatening to use nuclear weapons carries risks. It can backfire by galvanising the other side or breaking alliances. For example, Moscow’s nuclear threats have rallied NATO unity and prompted previously neutral countries to seek NATO protection. In East Asia, North Korea’s atomic boasts have led South Korea and Japan to strengthen their defence ties with the U.S., and even talk (quietly) about whether they need their own nuclear deterrents – a proliferation risk. So while nuclear brinkmanship might yield short-term leverage, it can also isolate and pressure the threatening state in the long run[86][87]. The value of tactical nuclear weapons, then, is a double-edged sword. Militarily, they offer no magic bullet – any gains on the battlefield could be outweighed by the escalatory response. Politically, their biggest impact is psychological: they remind the world that no matter how advanced our precision conventional weapons get, the most fearsome trump card remains a mushroom cloud.

Conclusion: The Precarious Threshold

The fact that we are even contemplating the use of “small” nuclear weapons in modern conflict is a sobering sign. The erosion of deterrence and the renewed talk of tactical nukes suggest that the world may be sleepwalking toward a nuclear threshold that had long seemed inviolable. Each of the nuclear-armed countries discussed – the United States, Russia, China, and North Korea – illustrates a different facet of this trend. The United States preaches restraint but has developed low-yield options to ensure it can deter or respond to limited nuclear use[88]. Russia publicly insists it would only use nukes defensively, yet it rattles the nuclear sabre to bolster its aggression and holds a vast inventory of tactical warheads ready for potential use[89][90]. China maintains a principled No First Use stance and avoids nuclear posturing, but its growing arsenal signals preparation for a more complex deterrence landscape[91]. And North Korea blatantly threatens first use of nuclear weapons, betting that extreme brinkmanship will safeguard its regime[92][93].

What each nation says about tactical nuclear weapons often diverges from what it does. Declared doctrines may reassure that nuclear arms are only for dire emergencies or retaliation, yet the deployment and development of ever more “usable” nukes tell another story. The truth is that as long as nuclear weapons exist, military and political leaders will be tempted to imagine ways to use them to their advantage. The long peace of the nuclear age – no use in war since 1945 – has fostered a kind of cognitive dissonance: We collectively recognise the apocalyptic danger of nuclear war, yet some believe that a limited or tactical use might be manageable or decisive. This thinking is fuelled by advances in technology (more precise delivery, lower yields) and by real-world pressures (conventional military imbalances, hardline ideologies, personalist regimes willing to take risks).

Ultimately, the question of whether a tactical nuclear strike would make an enemy back down or escalate is one we never want answered by experience. Optimists hope that the mere threat will suffice – deterrence will hold, as it has for so long. Pessimists warn that if the taboo erodes further, someone will eventually roll the dice. History provides plenty of instances where humanity stumbled into wars that many believed would never happen. A single miscalculation or provocation in a future crisis could result in the breaking of the nuclear firebreak. If that day comes, even if the weapon is “only” a tactical nuke, the world will be crossing into a dark new reality. As a recent analysis on the nuclear taboo put it, strengthening the norm against use is not just about avoiding immediate conflict; it’s about “ensuring the long-term survival and flourishing of humanity.”[94] For now, the best hope is that the taboo, though under strain, will continue to hold – and that tactical nuclear weapons will remain a theoretical horror rather than a practical one. The lesson of Hiroshima still looms large: once the nuclear genie is out of the bottle, stuffing it back in may be impossible. The challenge for global security is to prevent that genie from being tempted out at all, even by the smallest of nuclear lamps.