In a sobering assessment that echoes Cold War-era anxieties, the Stockholm International Peace Research Institute (SIPRI) released its Yearbook 2025 on June 16, providing a comprehensive overview of the world’s nuclear arsenals and the increasingly precarious geopolitical order underpinning them. For the first time in decades, the report confirms what many arms control analysts have feared: the global trend of nuclear disarmament has not only stalled but is reversing. The world is now firmly back on a trajectory of nuclear expansion, innovation, and modernization.
As of January 1, 2025, SIPRI estimates that there are 12,241 nuclear warheads worldwide, of which 9,614 are in military stockpiles, ready for potential use. Even more alarmingly, 3,912 warheads are deployed on operational delivery systems, with approximately 2,100 on high operational alert—primarily under the control of the United States and the Russian Federation.
The report presents not just a tally of arsenals but also a critical warning: the global nuclear order is entering an era of strategic instability, driven by eroding arms control frameworks, rising great-power competition, and rapid technological disruption. From Washington to Beijing, Moscow to Pyongyang, SIPRI’s findings portray a world where the nuclear genie is not just out of the bottle—it’s being reshaped, refined, and readied for an uncertain future.
While the Cold War arms race was largely a bipolar contest between the U.S. and USSR, today’s nuclear competition is multipolar and more complex. SIPRI outlines three major patterns across the nuclear landscape:
Modernization of legacy triads – including land-based intercontinental ballistic missiles (ICBMs), submarine-launched ballistic missiles (SLBMs), and nuclear-capable bombers.
Quantitative expansion, particularly by China, India, Pakistan, and North Korea.
Qualitative innovation, with MIRVs (Multiple Independently Targetable Reentry Vehicles), hypersonic delivery systems, cyber-capable command-and-control systems, and AI-based decision frameworks gaining prominence.
This arms buildup, SIPRI warns, is no longer constrained by formal treaties or norms. The end of the Intermediate-Range Nuclear Forces (INF) Treaty in 2019, the erosion of the Open Skies Treaty, and the upcoming expiration of the New START Treaty in 2026, with no successor in sight, have created a regulatory vacuum. The consequences could be profound.
Despite domestic political turbulence and budgetary concerns, the U.S. continues to pursue full-spectrum modernization of its nuclear triad:
- The Minuteman III ICBMs, operational since the 1970s, are being replaced by the LGM-35A Sentinel system.
- The Columbia-class submarines, expected to enter service in the early 2030s, are set to replace the aging Ohio-class SSBNs.
- A new air-launched cruise missile (ALCM) is in development to enhance the nuclear strike flexibility of U.S. bombers.
Perhaps more controversially, the U.S. has also begun work on new non-strategic (tactical) nuclear warheads, reviving concerns over lower-threshold uses of nuclear force. The B61-13 bomb, recently deployed to replace older B61s stationed in Europe, features dial-a-yield capabilities and GPS-guidance enhancements.
Yet, SIPRI raises concerns about the sustainability of this modernization effort, citing potential delays due to Congressional disputes over defense spending and broader debates about nuclear policy in an election year.
Russia maintains the world’s largest nuclear arsenal, but SIPRI reports increasing operational and technical challenges within its strategic modernization efforts.
The flagship RS-28 Sarmat “Satan II” ICBM program experienced another failure during tests in 2024, following delays in previous years. Other advanced systems—such as the nuclear-powered Burevestnik cruise missile and Poseidon underwater drone—are similarly behind schedule.
However, Russia continues to prioritize warhead reloading, aiming to increase the number of warheads per missile, especially on silo-based and mobile ICBMs. Additionally, the Russian military has revised its nuclear doctrine—announced in November 2024—to broaden scenarios under which nuclear weapons might be used, a move SIPRI calls “dangerously destabilizing.”
The new posture potentially includes responses to non-nuclear threats, such as major cyberattacks, conventional military defeats, or attacks on infrastructure. The implications for NATO and Eastern Europe are profound.
Among all nuclear-armed states, China is expanding the fastest. From an estimated 500 warheads in early 2024, its arsenal has surged to around 600 warheads, with projections to reach 1,500 by 2035.
What concerns SIPRI most is not just the numerical increase, but the infrastructure behind it. China has completed or nearly completed the construction of more than 300 new ICBM silos across remote desert and mountainous regions. While it is unclear how many of these silos are decoys or actively loaded, their scale and speed indicate a dramatic doctrinal shift.
Previously thought to keep warheads and missiles separated during peacetime, China may now be mounting some warheads on delivery systems even during peacetime, increasing responsiveness—and danger.
China is also investing in:
MIRV-capable DF-41 and DF-5C ICBMs
New-generation SSBNs (Type 096)
Dual-capable bombers and hypersonic gliders
This vertical integration of nuclear capabilities—land, sea, and air—has placed China firmly in the ranks of modernized triad holders, closing the qualitative gap with the U.S. and Russia.
The subcontinent remains a volatile flashpoint in global nuclear dynamics. SIPRI reports that India continues to develop MIRV-capable canisterized missiles, such as the Agni-V and Agni-P, which allow transport with mated warheads and may be maintained on alert.
Pakistan, meanwhile, is focusing on:
- Increasing fissile material production
- Developing new short-range systems like the Nasr missile
- Enhancing sea-based capabilities
The doctrinal emphasis in both states appears to be on survivability and credible second-strike—a potentially stabilizing development, if not for the risk of rapid escalation in crisis scenarios.
North Korea now possesses an estimated 50 assembled warheads and enough fissile material for 40 more, making it the world’s newest and most unpredictable nuclear power.
South Korean sources cited by SIPRI believe that Pyongyang is developing tactical nuclear weapons and preparing for theater-level deployments—a major shift from earlier emphasis on strategic deterrence.
Its tests in 2024:
- Solid-fuel ICBMs
- Hypersonic glide vehicles
- Submarine-launched ballistic missiles
These developments not only threaten the Korean Peninsula but could extend nuclear reach to Guam, Hawaii, and mainland U.S., altering strategic calculations in the Indo-Pacific.
Israel, while adhering to its policy of ambiguity, tested a missile propulsion system in 2024 that SIPRI believes could be linked to its Jericho missile series. Satellite imagery also revealed upgrades at the Dimona reactor, potentially indicating sustained fissile material production.
France is continuing development of its third-generation SSBN and a new air-launched cruise missile, while enhancing the payload of its M51 ballistic missile, reinforcing its independent deterrence.
The United Kingdom, although not expanding its stockpile in 2024, is still on track with the 2023 Integrated Review Refresh, which targets a ceiling of 260 warheads. The construction of four Dreadnought-class SSBNs is proceeding, set to replace the Vanguard class in the 2030s.
Beyond the number of warheads and missiles, SIPRI warns of a parallel arms race in emerging technologies, which may ultimately prove more destabilizing than raw nuclear capability.
- Warhead miniaturization, allowing smaller yields with greater tactical applications
- Artificial intelligence, especially in command-and-control decision chains
- Cyber capabilities, posing a risk of spoofed orders or data manipulation
- Hypersonic glide vehicles, which compress response timelines
- Antisatellite weapons, threatening space-based early-warning systems
Such technologies reduce decision-making time, increase first-strike incentives, and blur the line between conventional and nuclear engagements.
Perhaps the most troubling trend identified by SIPRI is the absence of meaningful arms control mechanisms.
The New START Treaty, currently the last major nuclear arms agreement between the U.S. and Russia, is due to expire in February 2026. With no replacement under negotiation, experts fear a return to unregulated deployments, rapid silo reactivation, and SSBN reload cycles unseen since the 1980s.
SIPRI concludes that unless urgent diplomatic initiatives are launched:
- The resilience of command-and-control systems will become a central concern.
- States may increasingly prioritize second-strike survivability.
- Doctrines may evolve to permit preemption, further destabilizing deterrence.
The SIPRI Yearbook 2025 does not merely report on nuclear trends—it marks the end of a decades-long illusion that nuclear disarmament was inevitable, even if gradual. In its place is a renewed, complex, and technologically advanced nuclear order that is less predictable, less stable, and more dangerous than ever.
The world is entering not just a new arms race, but a new nuclear era—one without the guardrails of the past. As strategic tensions rise and technologies race ahead of policy, the risks of miscalculation, accidental launch, or unauthorized use grow ever more acute.
