It has been over three decades since the Cold War ended, yet global nuclear arsenals are once again on the rise. Nuclear-armed powers large and small are modernising their weapons at a pace not seen in years[1]. The post-Cold War era of steadily shrinking stockpiles “is coming to an end”, warns Hans M. Kristensen of the Federation of American Scientists[2]. In 2025, the world’s nine nuclear states are collectively estimated to possess over 12,000 nuclear warheads, and for the first time in decades that number is growing rather than contracting[3]. This dangerous new arms race spans from the superpowers – the United States and Russia – to emerging nuclear players like North Korea and potentially Iran. Each nation’s buildup adds new tensions and technological complexities, stoking fears that the threat of nuclear warfare is advancing in tandem with these arsenals.

A New Nuclear Arms Race Begins

After the Soviet–US disarmament strides of the 1990s and 2000s, nuclear stockpiles fell dramatically. But recent data indicate that decline has halted. Nearly all nuclear-armed states are pursuing intensive weapons modernisation programmes – upgrading warheads and delivery systems or adding new ones[4]. Global inventory now stands at roughly 12,241 warheads (as of January 2025), of which about 9,614 are in military stockpiles ready for potential use[5]. Around 3,912 warheads are deployed on missiles or aircraft, with some 2,100 on high-alert launch-ready status – mostly in the U.S. and Russia[6]. Crucially, analysts note that “the era of reductions… is coming to an end” and a “clear trend of growing nuclear arsenals” has emerged[7]. Arms control agreements have crumbled, and sharpened nuclear rhetoric is replacing the cautious optimism of past decades[8].

To grasp the scope of this new arms race, consider the major nuclear players’ arsenals and recent developments:

Table: Estimated nuclear warhead inventories and notable developments by country (2025). “Stockpile” refers to active warheads available for use; total inventory includes retired warheads awaiting dismantlement.

The table above highlights the buildup across the board. Notably, the United States and Russia still hold roughly 90% of all nuclear warheads[35], and both are executing large-scale modernisation plans. Their stockpiles remained relatively stable in recent years under New START treaty limits[36]. However, with New START set to expire in 2026 and no replacement in sight, experts predict both powers may begin increasing deployed warheads afterward[37]. Indeed, unless a new agreement caps their arsenals, additional warheads could be loaded onto missiles or placed in reactivated launchers, reversing decades of warhead reductions[39].

Meanwhile, China’s nuclear expansion is the fastest of any nation. SIPRI estimates China has at least 600 warheads by 2025, up from ~290 just five years prior[41]. China has built hundreds of new missile silos in its western deserts, potentially enabling a much larger ICBM force by 2030[43]. If Beijing fully utilizes this new capacity, it “could potentially have at least as many ICBMs as either Russia or the USA by the turn of the decade”[44]. Even so, China’s warhead count would remain far below the superpowers’ – projections suggest ~1,500 Chinese warheads by 2035 (about one-third of current U.S. or Russian levels)[45]. Beijing continues to profess a doctrine of minimum deterrence and No First Use, keeping most warheads de-mated from missiles in peacetime[46]. However, its growing arsenal and the ambiguities in its posture (e.g. dual-capable missiles that blur conventional and nuclear roles) are raising global concerns[48].

The South Asian rivals, India and Pakistan, have engaged in their own quieter arms race. Each has an estimated 160–180 warheads and is slowly but steadily increasing that number[50]. India has been testing longer-range missiles that bring targets across China within reach, and working on submarine-launched nuclear missiles to achieve a full triad. Its new Agni-V ballistic missiles are canisterised – stored and launched from sealed tubes – which allows keeping them fuelled and potentially mated with warheads, drastically reducing launch time[51]. This could mark a shift from India’s traditionally de-mated posture. Pakistan, for its part, has focused on producing smaller, shorter-range nuclear weapons intended for battlefield use, in order to deter India’s superior conventional military. These include the Hatf-9/NASR mobile missiles designed to carry sub-kiloton to low-kiloton nuclear warheads for “tactical” strikes against invading forces[52]. Both nations have refrained from nuclear testing since 1998, but their stockpiles have roughly tripled since then. In early 2025, simmering tensions over Kashmir even spilled into a brief armed clash, during which strikes on nuclear-related sites and rampant misinformation “risked turning a conventional conflict into a nuclear crisis”[54]. This close call underscored how quickly an India–Pakistan confrontation could escalate out of control.

North Korea’s nuclear programme has evolved from a fledgling effort in the 2000s to a central pillar of the regime’s survival strategy. As of 2025, Pyongyang is believed to have built around 50 nuclear warheads and produced enough fissile material for perhaps 40 more[55]. In 2022–2023, North Korea made significant strides in missile capability, including test-launching the massive Hwasong-17 ICBM, which flew ~6,000 km into space on a lofted trajectory. Analysts note the Hwasong-17 – the largest road-mobile ICBM in the world – could potentially carry multiple warheads or decoys to penetrate defences[56]. Kim Jong Un has declared a policy of exponentially expanding the nuclear arsenal, calling for a “limitless” expansion of warhead production and missile development[57]. North Korea is also reportedly in the final stages of developing a tactical nuclear weapon – a smaller warhead for short-range delivery, aimed at targets in South Korea or regional US bases[58]. These advancements come on top of its prior successful tests of a thermonuclear bomb (claimed yield in the hundreds of kilotons) and numerous medium-range missiles. North Korea’s unchecked buildup has already altered Northeast Asia’s security landscape, spurring debates in Seoul and Tokyo about strengthening their own deterrence (including, for South Korea, discussion of hosting US nuclear assets or even developing its own nukes)[59]. The risk remains that any new Korean conflict, even a conventional one, could trigger Pyongyang’s use of nuclear weapons early on – with catastrophic results.

Finally, Iran sits at the threshold of the nuclear club, inching ever closer to a weapons capability. Tehran is generally believed to not yet have a nuclear bomb, and remains (at least nominally) under the monitoring of the International Atomic Energy Agency (IAEA). Yet Iran’s nuclear programme has advanced significantly in recent years beyond the limits of the defunct 2015 nuclear deal. By 2024–2025, Iran had accumulated a stockpile of over 9,000 kg of enriched uranium, including more than 400 kg at 60% enrichment – a level just short of weapons-grade[60]. This quantity of near-weapons-grade uranium, if further enriched to around 90%, would be sufficient for several nuclear warheads[61]. Iran has also installed more advanced centrifuges and even announced construction of a new enrichment facility dug into a mountain (to better protect it from airstrikes)[62]. The IAEA’s Board of Governors formally rebuked Iran in June 2025 for failing to fully cooperate with inspectors, after evidence of undeclared nuclear materials and activities emerged[63]. Tehran, however, has been opaque about its intentions – insisting it seeks nuclear technology only for energy and research, while simultaneously reducing transparency. This precarious situation has Israel (which views a nuclear-armed Iran as an existential threat) considering more drastic measures. Israeli officials have hinted at the possibility of pre-emptive strikes on Iranian nuclear sites if diplomacy fails – a scenario that could ignite a wider Middle East war. In short, Iran’s advances mean it has become a “nuclear threshold state”: it may only be a matter of months away from a bomb if its leadership makes that fateful decision[64].

Sophisticated Arms and Emerging Dangers

The qualitative evolution of nuclear arsenals is as striking as the quantitative growth. Today’s arms race is not just about how many warheads each country has, but also what kind of weapons and technologies are being developed. Several technological advancements are reshaping the nuclear threat – often in destabilising ways that could increase the chance of a nuclear exchange. Unlike the relatively static U.S.–Soviet standoff of the Cold War, the new race involves multiple actors and cutting-edge tech. Consider some key developments:

• Hypersonic Weapons: Both Russia, China and now the U.S. have been testing or deploying missiles that travel at least five times the speed of sound and can manoeuvre unpredictably. Russia’s Avangard boost-glide vehicle, for example, can deliver a ~2 megaton nuclear warhead while evading interceptors[65]. It entered limited service in 2019 atop ICBMs. Moscow has also fielded the air-launched Kinzhal and ship-launched Zircon hypersonic missiles – both nuclear-capable[67]. These weapons shrink warning and reaction times for the side under attack, potentially pressuring nuclear forces to adopt a “launch on warning” posture to avoid losing their missiles. The globe-circling speed of hypersonics and their unpredictable flight paths raise the risk of miscalculation, since leaders may have mere minutes to decide how to respond to alerts. A false alarm in such circumstances – not unheard of even with older technology – could be deadly under time crunch. As a result, hypersonics are seen as highly destabilising: they amplify the hair-trigger dilemma that plagued Cold War strategists, now with even less margin for error.
• “Exotic” Delivery Systems: Russia in particular has showcased novel nuclear delivery systems that seemed ripped from science fiction. The Poseidon nuclear torpedo – a robotic, nuclear-propelled submersible – is designed to carry a multi-megaton warhead into coastal areas, detonating offshore to swamp cities with a radioactive tsunami[69]. A prototype Poseidon was reportedly produced and delivered for testing on a special submarine, though full deployment isn’t expected until later this decade[71]. Another is the 9M730 Burevestnik, a nuclear-powered cruise missile with theoretically unlimited range[72]. In theory, Burevestnik could fly evasive routes around the globe under the radar. In practice, it has suffered numerous test failures and remains far from operational[73]. These “doomsday” devices, if perfected, could be hard to defend against and have outsized psychological impact. However, experts debate whether they have much military utility beyond terror – Poseidon, for instance, would cause massive radioactive fallout affecting friend and foe alike[74]. Still, the very existence of such weapons contributes to an atmosphere of unpredictability.
• Dual-Use Missiles & Warhead Ambiguity: An increasing number of delivery systems can carry either a nuclear or a conventional payload, and adversaries might not be able to tell the difference until impact. This warhead ambiguity is notably concerning with China’s arsenal. For example, the Chinese Dongfeng-26 (DF-26) intermediate-range ballistic missile is dual-capable – it can be fitted with either a nuclear warhead or a conventional one[76]. The People’s Liberation Army has even practised swapping a DF-26’s warheads in the field, demonstrating how quickly it could go from conventional mode to nuclear[78]. If a conflict breaks out, the launch of such a missile poses a nightmare dilemma: the opponent’s early warning systems may detect an incoming missile, but not know if it carries a nuclear warhead[79]. For instance, if China fired a DF-26 toward a U.S. carrier group, American commanders might assume the worst (a nuclear strike) and consider retaliating with nuclear weapons – even if the missile was actually conventional. This vastly increases the risk of inadvertent nuclear war, triggered by misinterpretation. Russia’s deployment of conventional missiles that have nuclear variants (like Iskander short-range missiles or Kalibr cruise missiles) poses similar risks in Europe. In essence, the entanglement of nuclear and non-nuclear strike systems means any military clash involving these powers could be one misjudgement away from escalation to the nuclear level[81].
• Artificial Intelligence and Automation: Advances in AI are being explored for applications in early-warning networks, decision support, and even autonomous weapon systems. While AI can potentially improve reaction speed and sift through data faster than humans, it also introduces new failure modes. Experts warn that as AI speeds up decision-making in crises, the likelihood of a mistake grows[83]. An algorithm might misidentify a flock of birds or a space launch as an incoming missile attack, or conversely, fail to recognize a real attack in time – and a military relying on AI could launch or hesitate based on that faulty analysis. Cyber warfare compounds this issue: AI or not, highly digitalised command systems could be hacked or spoofed by adversaries, feeding false data to decision-makers. The nightmare scenario is a “flash war” sparked by an AI or sensor error that convinces one side it is under nuclear attack and must respond immediately. The 20th-century incidents of near-launch due to false alarms (e.g. the 1983 Soviet false alarm or the 1995 Norwegian rocket incident) show how perilous miscommunication can be. With faster tech and less human-in-the-loop time, the 21st-century version could have no failsafe. As SIPRI Director Dan Smith cautions, with new technologies in play, “there is a higher risk of a nuclear conflict breaking out as a result of miscommunication, misunderstanding or technical accident”[85]. In short, automation without adequate caution could accelerate us straight into Armageddon by accident.
• Missile Defences and Anti-Satellite (ASAT) Weapons: The continued improvement of missile defence systems – like the U.S. expanding its interceptors or new theatre defence like THAAD – while purely defensive, can paradoxically drive offensive arms buildups. Nuclear powers fear that if their adversary can shoot down some of their missiles, their deterrent is weakened; they may respond by building more missiles or MIRVing warheads (putting multiple warheads on one missile) to overwhelm defences. This offence–defence cycle is one factor in China’s current expansion[87], as it eyes U.S. missile defences. Similarly, Russia’s development of hypersonic glide vehicles and ultra-heavy ICBMs aims to ensure its warheads can evade or swamp U.S. defences. On another front, the weaponisation of space threatens nuclear stability. Several nations (U.S., Russia, China, India) have tested anti-satellite missiles that can destroy satellites in orbit. In a conflict, knocking out a rival’s early-warning or communication satellites would cripple their ability to detect launches or maintain command and control – potentially tempting a pre-emptive nuclear strike out of “use them or lose them” fear. Even the testing of these systems creates debris that endangers space assets. The interplay of space and missile defence tech means nuclear arsenals cannot be viewed in isolation; the overall strategic balance now involves multiple domains.

In sum, the 2025 arms race is not a simple numerical contest. It is “gearing up with much more risk and uncertainty than the last one”, in Dan Smith’s words[88]. The mix of more nuclear-armed countries, faster and stealthier missiles, cyber-AI complexities, and blurred nuclear-conventional lines makes the current situation extraordinarily volatile. Traditional arms control – mostly based on bilateral U.S.–Soviet treaties counting launchers and warheads – is struggling to keep up. Old formulas no longer suffice[89], since “who is ahead” is now as much about qualitative edge and cyber resilience as about counting warheads. With major arms control agreements like INF and Open Skies already dead, and New START on life support, the guardrails that helped prevent a nuclear spiral are coming off just as the road has become more hazardous.

The Rising Spectre of Nuclear War

What would it actually mean if these weapons – old or new – were ever used? In a word: catastrophe. The advances in nuclear technology have, if anything, increased the destructive potential of arsenals. Even the so-called “low-yield” or tactical nuclear weapons being fielded today pack destructive power comparable to the bombs that levelled Hiroshima and Nagasaki. A 10-kiloton warhead (considered a small tactical nuke) could still annihilate several city blocks, with blast and fires killing hundreds of thousands in a dense urban area – not far off from the ~15 kt “Little Boy” bomb that obliterated Hiroshima in 1945[90]. At the high end, modern strategic warheads can be 100 times more powerful. For instance, Russia’s Avangard glide vehicle can carry a ~2 megaton warhead[91]; just one such warhead could vaporise the downtown core of a major metropolis and ignite firestorms over many tens of square miles. The immediate death toll in a single large nuclear blast could reach millions, especially in today’s mega-cities.

It’s hard to overstate the sheer horror of a large-scale nuclear exchange. A full-blown war between the United States and Russia – involving thousands of warheads targeting cities and missile silos – would essentially destroy both nations and devastate the planet. Studies suggest the direct casualties in a massive U.S.–Russia nuclear war would number in the hundreds of millions of people, essentially wiping out the population of entire countries in hours. Moreover, the environmental effects could be global and long-lasting. Scientists have long warned of nuclear winter – firestorms from burning cities would loft vast quantities of soot into the upper atmosphere, blocking sunlight. The result: crop-killing cold and dark that could last for years, even far from the bombed areas[92].

Even a “limited” regional nuclear war could wreak worldwide havoc. For example, a scenario studied by climate scientists looked at an Indo-Pakistani nuclear exchange involving 100 atomic bombs (about the size of Hiroshima’s blast) – which is less than 1% of the global nuclear arsenal. The outcome would be unprecedented global famine. Firestorms ignited by those 100 detonations would inject an estimated 5 million tonnes of black soot into the stratosphere[94]. Models predict global temperatures would drop by ~1.5–2°C on average for several years[95]. That doesn’t sound huge, but it would shorten growing seasons and batter food production. Yields of major crops would fall dramatically; worldwide grain output might drop ~11% on average for 5 years, with the worst declines (20% or more) in temperate food-exporting regions[97]. As a Columbia University study bluntly concluded, even a limited war between India and Pakistan “would have devastating indirect implications worldwide,” potentially exceeding “the largest famine in documented history”[99]. Over a billion people could be at risk of starvation in the ensuing decade. Another research team found that such a war could kill 50–125 million people outright within a week – more than the total deaths in World War II – and then lead to collapse of global food systems, threatening billions more[101].

In short, any notion that nuclear wars could be contained or fought “surgically” is wishful thinking. Once the nuclear threshold is crossed, escalation would be hard to control. Nuclear weapons obliterate cities, but their effects do not stop at national borders. Radioactive fallout drifts with the winds, potentially contaminating regions far away. A nuclear strike on South Korea or Poland, for instance, would not only kill those in the blast but could spread radiation to neighbours. And the climatic disruptions from burning cities (soot, ash, climate cooling) could imperil people who weren’t even involved in the conflict, as detailed above.

As of 2025, the world is keenly aware of these stakes. The Doomsday Clock – a symbolic gauge by the Bulletin of the Atomic Scientists – was moved to just 90 (and now 89) seconds to midnight, the closest it has ever been to apocalyptic disaster[103]. The Bulletin’s science board cited the war in Ukraine, rising nuclear stockpiles, and erosion of arms control as prime reasons for this dire outlook[104]. They noted somberly that all the nuclear-armed countries are investing hundreds of billions into weapons “that can destroy civilisation many times over.”[106] The implication is clear: humanity’s destructive capacity is soaring just as the mechanisms to rein it in are faltering.

Conclusion

In 2025, a new and precarious arms race is underway. The United States, Russia, and China are entrenching themselves in a three-way competition of nuclear one-upmanship, while regional powers like India, Pakistan, and North Korea build up arsenals that could ignite their own local arms races. Iran’s nuclear advances add further volatility to an already fraught Middle East. This acceleration in nuclear capabilities comes accompanied by dangerous technological shifts – from hypersonic delivery systems to AI-driven command networks – that render the geopolitical landscape even more accident-prone and unpredictable[107].

History offers a warning. During the Cold War, humanity survived several close shaves with nuclear annihilation thanks to a combination of luck, cautious leadership, and later, arms control agreements. Today, however, those agreements are fraying, rhetoric is heating up, and new technologies threaten to outpace human control. The world’s nuclear arsenals are smaller than at Cold War peaks, but the weapons are more advanced and proliferated across more states. The threat of nuclear warfare is, by many expert accounts, at its highest in decades. A single spark in the wrong place – a border skirmish, a radar glitch, or a terrorist provocation – could unleash devastation on a scale that defies imagination.

What lies ahead? If current trends continue, the late 2020s and 2030s may see more nuclear-armed states, larger arsenals, and multi-sided nuclear rivalries (U.S.–Russia–China, India–Pakistan–China, etc.) with few treaties to constrain them. The world will have to navigate this new arms race with extreme care. As one analyst put it, nuclear weapons may provide a sense of deterrence, but “they also come with immense risks of escalation and catastrophic miscalculation”[109]. In the end, the renewed nuclear buildup of 2025 is a stark reminder: as long as these armaments exist and multiply, the shadow of Armageddon looms over us all – and the price of a single misstep could be unthinkably high.