States are reaching for nuclear solutions and fueling arms-race dynamics.
In Stockholm, researchers have documented what may be the most consequential reversal in post-Cold War security: all nine nuclear-armed states are expanding and modernizing their arsenals, while the treaties and diplomatic channels designed to prevent catastrophic miscalculation quietly expire around them. With 12,187 warheads now counted and no successor to the New START treaty in place, humanity finds itself in a new era of nuclear competition — one that lacks even the imperfect guardrails of the Cold War. The May 2025 conflict between India and Pakistan, in which nuclear-capable bases were struck, offered a glimpse of how quickly deterrence logic can fail when tested by real events.
- Every one of the world's nine nuclear-armed states ran active modernization programs in 2025, with China expanding fastest — potentially matching superpower ICBM counts by 2030.
- The New START treaty expired in February 2026 with no replacement, stripping away the last binding legal constraint on Russian and American strategic nuclear forces.
- A third consecutive NPT Review Conference collapsed without agreement, signaling that the international non-proliferation architecture is fracturing rather than holding.
- India and Pakistan's brief May 2025 war included strikes on nuclear-capable military sites, proving that nuclear deterrence does not reliably prevent armed conflict between nuclear states.
- European nations are now pursuing nuclear-sharing arrangements with France and the UK, while Russia has stationed nuclear weapons in Belarus — reshaping the continent's strategic geography.
- SIPRI's director warns of a self-reinforcing cycle in which each state's pursuit of security deepens collective insecurity, with no diplomatic habits or institutions yet capable of breaking the loop.
On a June morning in Stockholm, the Stockholm International Peace Research Institute released findings that cut against three decades of nuclear diplomacy. Its 2026 Yearbook documents a reversal so complete it amounts to an abandonment of the disarmament commitments nuclear-armed states made when the Cold War ended.
As of January 2026, the world held an estimated 12,187 nuclear warheads, with roughly 4,000 actively deployed on missiles and aircraft and over 2,000 sitting on ballistic missiles in a state of constant readiness. For decades the trend had moved the other way — Russia and the United States, which together hold 83 percent of all stockpiled warheads, had been dismantling retired weapons faster than they deployed new ones. That pattern is ending.
All nine nuclear-armed states pursued modernization in 2025. China is expanding fastest, now estimated at around 620 warheads and loading missiles into newly constructed silo fields at a pace that could see it match superpower ICBM counts by 2030. Russia tested new cruise missiles and began building forward bases in Belarus. France announced it would increase its arsenal and stop publicly disclosing its size. The United Kingdom reversed its post-Cold War denuclearization of its air force. India, Pakistan, and North Korea all expanded delivery capabilities.
What makes this expansion especially dangerous, SIPRI researchers argue, is that it coincides with a collapse in the mechanisms designed to prevent miscalculation. The New START treaty expired in February 2026 with no successor. The NPT Review Conference ended in May without a final document — the third consecutive failure. Nuclear states have grown more secretive, communication channels have deteriorated, and some have drifted toward authoritarianism, raising questions about whether leaders would receive accurate information in a crisis.
The human stakes became visible in May 2025, when India and Pakistan fought a brief armed conflict in which Indian forces struck Pakistani bases with nuclear-related functions. Both sides stepped back from the brink, but the episode demonstrated that nuclear deterrence does not reliably prevent war. SIPRI's director warned that a self-reinforcing cycle has taken hold — great powers pursuing security in ways that deepen collective insecurity — and that the world is entering an era of nuclear competition without the guardrails, or the diplomatic habits, that kept the Cold War from becoming catastrophic.
On a June morning in Stockholm, researchers at the Stockholm International Peace Research Institute released findings that cut against three decades of nuclear diplomacy: the world's nine nuclear-armed states are building up their arsenals again, not scaling them down. The 2026 Yearbook, the institute's annual accounting of global weapons and security, documents a reversal so complete that it amounts to an abandonment of the disarmament commitments these nations made when the Cold War ended.
The numbers tell the story plainly. As of January 2026, the world contained an estimated 12,187 nuclear warheads. Of those, roughly 9,745 existed in military stockpiles ready for use. About 4,012 were actively deployed on missiles and aircraft. Between 2,100 and 2,200 sat on ballistic missiles in a state of constant readiness, waiting for launch orders that might never come. For decades, the trend had moved in the opposite direction—Russia and the United States, which together hold 83 percent of all stockpiled warheads, had been gradually dismantling retired weapons faster than they deployed new ones. That pattern is ending. The pace of dismantlement is slowing. The pace of deployment is accelerating.
The nine states—the United States, Russia, the United Kingdom, France, China, India, Pakistan, North Korea, and Israel—all pursued modernization programs in 2025, and most introduced new nuclear-capable systems during the year. China is expanding its arsenal faster than any other nation. SIPRI estimates it now possesses around 620 warheads and is loading hundreds of missiles into newly constructed silo fields. If China continues at its current pace, it could match the number of intercontinental ballistic missiles held by Russia or the United States by 2030. Russia tested new cruise missiles and began constructing forward bases for intermediate-range weapons in Belarus. The United States is pursuing a comprehensive modernization effort, though budget constraints and planning delays have complicated the work. France announced in March 2026 that it would increase the number of warheads in its arsenal and stop publicly disclosing its arsenal size. The United Kingdom, which had denuclearized its air force in the 1990s, reversed course and announced plans to acquire nuclear-capable fighter jets. India and Pakistan both expanded their arsenals and continued developing new delivery systems. North Korea, which does not acknowledge its weapons program but is believed to possess around 60 assembled warheads, accelerated fissile material production and tested new missile designs.
What makes this expansion particularly dangerous, according to SIPRI Director Karim Haggag, is that it is happening alongside a collapse in the mechanisms designed to prevent miscalculation. The New START treaty, which had limited Russian and American strategic nuclear forces since 2010, expired in February 2026 with no successor agreement in place. The 2026 Review Conference of the Nuclear Non-Proliferation Treaty ended on May 22 without producing a final outcome document—the third consecutive review conference to fail in this way. Nuclear-armed states have grown more secretive about their arsenals and their intentions. Direct communication channels between certain nuclear powers have deteriorated or vanished. Some nuclear-armed nations have drifted toward authoritarianism, raising questions about whether leaders would receive accurate information during a crisis or act rationally under pressure.
The human dimension of this shift became visible in May 2025, when India and Pakistan fought a brief armed conflict. Indian forces attacked Pakistani air and missile bases with nuclear-related functions. Both sides took steps to avoid escalation, but the episode demonstrated that nuclear deterrence logic—the assumption that possession of nuclear weapons prevents war—does not always hold. Hans M. Kristensen, a senior researcher at SIPRI, observed that states are "reaching for nuclear solutions" and in doing so are "creating new risks and fuelling arms-race dynamics."
The breakdown extends beyond the superpowers. Several European nations, including Germany, have expressed interest in nuclear-sharing arrangements with France and the UK in addition to existing arrangements with the United States. President Emmanuel Macron announced in March 2026 that France was already in dialogue with Germany and the UK about such arrangements, and that other European states had expressed interest. Russia and Belarus have claimed that Russia has deployed nuclear weapons on Belarusian soil, and in December 2025 Russia released video evidence of a dual-capable missile operating inside Belarus.
The institute's director warned that a self-reinforcing cycle has taken hold. Great powers seek to protect their security and dominance in ways that deepen overall insecurity. Trade has become weaponized. Technology, supply chains, water, and energy have become tools of geopolitical competition. If these trends continue unchecked, Haggag said, they could undermine strategic stability itself. The world is entering a period of nuclear competition without the guardrails that existed during the Cold War—and without the diplomatic habits that kept that competition from becoming catastrophic.
Notable Quotes
Making national defence strategies dependent on nuclear weapons could significantly increase nuclear risks, especially as weapon technology advances and geopolitical tensions rise.— Karim Haggag, SIPRI Director
Nuclear weapon states are sidelining their disarmament commitments and flexing their nuclear muscles, creating new risks and fueling arms-race dynamics.— Hans M. Kristensen, SIPRI Weapons of Mass Destruction Programme
The Hearth Conversation Another angle on the story
Why does it matter that China is expanding faster than anyone else? Isn't 620 warheads still far fewer than Russia or the US?
The number itself matters less than what it signals. China is building capacity—silos, missiles, fissile material production. If it reaches parity with Russia or the US by 2030, that changes the entire strategic calculation. Right now, two powers dominate. In a decade, there could be three. That's a different game.
You mentioned the India-Pakistan conflict in May 2025. How close did that come to nuclear use?
No one knows. Both sides attacked military bases with nuclear functions. Both sides also pulled back. The fact that they managed restraint is almost beside the point—the fact that nuclear-armed states are now fighting each other at all undermines the whole theory that nuclear weapons prevent war.
What's the significance of New START expiring with no replacement?
For 16 years, Russia and the US had a treaty that limited their strategic arsenals and required transparency. They knew what each other had. They could talk about it. Now there's nothing. No limits, no verification, no conversation. In a world where tensions are already high, that's a dangerous void.
The report mentions "strategic ambiguity." What does that mean in practice?
It means states are deliberately unclear about what they have, where they have it, and when they might use it. France just announced it won't disclose its arsenal size anymore. Russia claims it has deployed weapons in Belarus but won't confirm details. When you can't see what your adversary has, you assume the worst. You build more to be safe. Everyone builds more.
Is there any mechanism left to slow this down?
The Non-Proliferation Treaty still exists, but it's weakening. The review conference just failed for the third time in a row. The grand bargain was simple: non-nuclear states agree not to build weapons if nuclear states move toward disarmament. That bargain is broken. Nuclear states are doing the opposite. Why would anyone trust it now?