A widening stalemate between the United States and Iran over Tehran’s nuclear program has added fresh strain to an already volatile global nuclear landscape, according to a new assessment by the Stockholm International Peace Research Institute (Stockholm International Peace Research Institute). The report finds that all nine nuclear-armed states—the United States, Russia, United Kingdom, France, China, India, Pakistan, North Korea, and Israel—continued modernizing or expanding their nuclear arsenals in 2025, with most deploying new nuclear-capable delivery systems during the year.
The report highlights a marked acceleration in nuclear competition, particularly in Asia, where five nuclear-armed states—Russia, China, India, Pakistan, and North Korea—are simultaneously expanding capabilities, developing new delivery systems, and accumulating fissile material. SIPRI warns that the global trend of gradual reduction in nuclear inventories, driven for decades by dismantlement of retired warheads, is now at risk of reversal as modernization programs outpace decommissioning.
According to SIPRI’s 2025 estimates, global nuclear stockpiles increased by 141 warheads over the year, bringing the total worldwide inventory to approximately 9,745 nuclear weapons. The increase was driven primarily by four countries: Russia, China, India, and North Korea. By contrast, the arsenals of the United States, the United Kingdom, France, and Israel remained broadly stable.
Russia continues to maintain the world’s largest nuclear arsenal, with approximately 4,400 warheads. SIPRI reports that Russia added 91 warheads in 2025 alone, accounting for more than half of the global net increase.
The United States remains second with about 3,700 warheads but did not add new nuclear weapons to its stockpile in 2025, continuing a policy of maintaining rather than expanding its deployed arsenal.
China is the fastest-growing major nuclear power, with an estimated 620 warheads after adding roughly 20 in 2025. Analysts note that China’s expansion reflects broader efforts to diversify and strengthen its nuclear deterrent posture, including development of new missile silos and delivery systems.
In Europe, both France and United Kingdom maintained relatively stable arsenals, with approximately 290 and 225 warheads respectively, while continuing modernization programs focused on submarine-based deterrents.
SIPRI emphasizes that Asia is now the epicenter of nuclear expansion. In addition to China’s buildup, both India and North Korea expanded their arsenals in 2025. India added roughly 20 warheads, bringing its total to about 190, while North Korea increased its estimated stockpile to around 60 warheads, adding about 10 over the year.
Although Pakistan did not add new warheads in 2025, SIPRI notes that it continued to develop new delivery systems and expand fissile material production capabilities. Pakistan’s estimated arsenal remains at roughly 170 warheads, but analysts caution that continued production infrastructure could enable further expansion in the coming decade.
SIPRI’s report warns that this pattern of simultaneous modernization among all regional nuclear actors is intensifying strategic uncertainty in South Asia and East Asia, where multiple unresolved territorial disputes and military rivalries already exist.
Nowhere is the risk more acute than in South Asia, which analysts frequently describe as the world’s most dangerous nuclear flashpoint. India and Pakistan, both nuclear-armed neighbors with a history of military confrontation, have continued to develop increasingly sophisticated missile systems and warfighting doctrines.
The report references a brief but intense escalation between India and Pakistan in May 2025, which reportedly remained below the nuclear threshold but demonstrated how rapidly conventional conflict could escalate under nuclear shadow conditions. SIPRI notes that such crises are testing traditional assumptions about nuclear deterrence stability.
According to the institute, “world events, including conflict between nuclear-armed states, are challenging established deterrence logic,” raising concerns that future crises could spiral unpredictably if escalation control mechanisms fail.
Pakistan’s nuclear trajectory remains one of the most closely scrutinized aspects of the global nuclear order. While its warhead count remained stable in 2025, its qualitative modernization continues. The country is pursuing what it describes as “full-spectrum deterrence,” encompassing strategic, operational, and tactical nuclear capabilities designed to counter conventional military superiority.
Pakistan’s arsenal includes a range of ballistic and cruise missile systems, including short- and medium-range platforms such as Shaheen, Ghauri, and Abdali variants, as well as the NASR (Hatf-9) short-range system, which is widely viewed as a tactical nuclear weapon designed for battlefield use. Analysts argue that such systems lower the nuclear threshold by introducing nuclear options into conventional battle scenarios.
The air leg of Pakistan’s nuclear forces is believed to rely on dual-capable aircraft such as F-16 and Mirage platforms, while cruise missiles such as the Ra’ad system provide additional air-launched strike capability. At sea, Pakistan has tested submarine-launched cruise missile technology, signaling an ambition to develop a survivable second-strike capability.
The institute also notes continued concerns regarding fissile material production. While Pakistan’s stockpile is estimated at approximately 170 warheads, projections suggest it could grow toward 200 in the late 2020s if enrichment and reprocessing capacities continue expanding.
The nuclear balance in South Asia is further complicated by differing doctrines. India maintains a declared posture of massive retaliation, signaling that any nuclear use would trigger overwhelming response. This creates a high-risk escalation dynamic if tactical nuclear weapons are ever introduced into a conflict.
Pakistan, by contrast, has emphasized deterrence flexibility, including the potential use of low-yield weapons under extreme conventional threat scenarios. This doctrinal divergence is widely cited by analysts as a key instability driver in the region.
SIPRI’s findings align with assessments from the Bulletin of the Atomic Scientists, which also highlights ongoing modernization of missile forces, including infrastructure developments observed via satellite imagery at military facilities. The report notes continued improvements in mobility, range, and survivability of delivery systems across Pakistan’s nuclear force structure.
Pakistan’s development of longer-range missile systems has also drawn international scrutiny. In late 2024, the United States Department of State imposed sanctions on entities linked to Pakistan’s missile development programs, citing concerns over efforts to expand the range and sophistication of delivery systems.
U.S. officials have warned that continued advances in ballistic missile technology could eventually extend reach beyond South Asia, raising long-term proliferation concerns. While Pakistan denies any offensive intent beyond regional deterrence, analysts note that technological trajectories often outlast declared policy intentions.
Across all nuclear-armed states, SIPRI identifies a common pattern: modernization is accelerating even where total warhead numbers remain stable. Submarine-based systems, hypersonic research, missile defense upgrades, and command-and-control enhancements are being prioritized, signaling a shift toward more survivable and flexible nuclear postures.
At the same time, the pace of dismantlement of retired warheads has slowed significantly compared to the post-Cold War era. For decades, reductions in US and Russian stockpiles masked increases elsewhere. That equilibrium is now weakening.
The report warns that if current trends continue, the world could enter a phase of net nuclear expansion after decades of gradual decline.
The 2025 SIPRI assessment paints a picture of a more fragmented and competitive nuclear order, where multiple regional rivalries intersect with great-power competition. The simultaneous modernization efforts of all nine nuclear-armed states suggest that nuclear weapons remain central—not peripheral—to global security planning.
While the US–Iran nuclear impasse adds another layer of diplomatic tension, the broader structural trend is clear: nuclear deterrence is becoming more complex, more regionalized, and potentially less stable.
Nowhere is this more evident than in Asia, where overlapping nuclear expansions in China, India, Pakistan, and North Korea are reshaping the strategic landscape. As modernization accelerates and doctrinal differences persist, SIPRI concludes that the risk of miscalculation—however small—carries increasingly severe consequences for regional and global security alike.
