STOCKHOLM — Nine nuclear-armed states upgraded and expanded their nuclear arsenals over the past year, according to a report by the Stockholm International Peace Research Institute (SIPRI). Most of these states deployed new nuclear-armed or nuclear-capable weapon systems.
Nuclear-armed states have reduced their involvement in nuclear demobilization efforts that characterized previous decades. The SIPRI report indicates these actions reverse a historical decline in global nuclear stockpiles observed since the end of the Cold War. "The evidence is growing that the nuclear weapon states are sidelining, and even walking away from, their disarmament commitments and are instead flexing their nuclear muscles." SIPRI researcher Hans Kristensen said.
As of January, the nine nuclear powers possessed 12,187 nuclear warheads. Approximately 9,745 of these were held in military stockpiles for potential use. An estimated 4,012 warheads were deployed with missiles and aircraft, and up to 2,200 were maintained on high alert for rapid launch. Nearly all high-alert nuclear warheads belonged to Russia, the United States, France, or the United Kingdom.
Russia and the United States possess an estimated 83% of warheads available for military use and nearly 86% of all nuclear weapons globally. Modernization programs by nuclear states are expected to increase the size and diversity of their arsenals. The anticipated reversal of declining stockpiles is attributed to a slowdown in dismantling retired warheads and an acceleration in deploying new weapons by leading nuclear powers.
China's nuclear arsenal increased from approximately 600 to 620 warheads over the past year, expanding at a faster rate than any other nuclear-armed state. India slightly increased its nuclear arsenal in 2025 and continued developing new types of nuclear delivery systems. Pakistan also continued developing new nuclear delivery systems and accumulating fissile material in 2025.
The United Kingdom maintained its existing nuclear arsenal size, although its operational warhead stockpile is projected to increase. France announced plans to increase its number of nuclear warheads and will no longer publicly disclose the size of its arsenal. North Korea has assembled an estimated 60 nuclear warheads and continues developing capabilities to expand its arsenal. Israel, which maintains a policy of nuclear ambiguity, is estimated by SIPRI to possess approximately 90 nuclear warheads; construction activity at the Negev Nuclear Research Center near Dimona increased in 2025.
No independent assessment was available for this report.