Sipri warns of a new nuclear arms race as all nine atomic powers expand and modernise arsenals

A global rearmament cycle

All nine nuclear-armed states — the United States, Russia, China, the United Kingdom, France, India, Pakistan, North Korea and Israel — continued to modernise and expand their arsenals in 2025, according to the Stockholm International Peace Research Institute's (Sipri) 2026 yearbook. The total global inventory stood at an estimated 12,187 warheads in January 2026, a slight dip from 12,241 a year earlier. Sipri researchers attribute the decline solely to the United States and Russia dismantling retired warheads, a process that is slowing down.

We are already in the middle of a new nuclear arms race. Every nuclear state is expanding its nuclear arsenal either quantitatively or qualitatively — and some are doing both.

The number of warheads in military stockpiles for potential use rose from 9,614 to 9,745. Of those, roughly 4,012 were deployed on missiles or at bases with operational forces, about 100 more than the previous year. Between 2,100 and 2,200 warheads were kept on high operational alert on ballistic missiles, almost all belonging to Russia and the United States.

The collapse of arms control

A key driver of the deteriorating security environment is the expiration of the New Start treaty between Russia and the United States in February 2026. No successor agreement was reached. Sipri researcher Matt Korda noted that both major nuclear powers could now theoretically load many hundreds of additional warheads onto existing delivery systems without building a single new launcher. Without treaties, nuclear-armed states are also increasingly choosing to withhold key details about their nuclear capabilities.

There are more and more signs that nuclear-armed states are neglecting their disarmament obligations or even abandoning them completely, instead showing off their nuclear strength.

Shifting arsenals and new technologies

Russia and the United States together hold roughly 83 percent of all stored nuclear warheads, with an estimated 5,420 and 5,042 respectively. Their combined share of operational warheads has fallen from 90 percent in 2025 as France, the United Kingdom and China accelerate deployments. China is expanding its arsenal the fastest and could, within a few years, possess as many land-based intercontinental ballistic missiles as Russia or the United States. France, the world's fourth-largest nuclear power, announced in March 2026 that it would increase its warhead stockpile.

Sipri also flagged the emerging role of artificial intelligence in nuclear command, control and communications (NC3) systems. While AI has not yet been integrated into high-risk nuclear systems, its use in satellite, radar and communication networks has been confirmed, though its exact functions remain difficult to predict.

Deterrence thinking spreads to non-nuclear states

The report documents a growing appetite for nuclear deterrence among states that do not currently possess atomic weapons. Polish Prime Minister Donald Tusk said in March that his country would be safer with its own arsenal. South Korean politicians have been calling for indigenous nuclear weapons for years. Pakistan's Defence Minister Khawaja Asif suggested the country could make its nuclear capabilities available to partner state Saudi Arabia.

French President Emmanuel Macron has raised the prospect of extending France's nuclear umbrella to Norway, Lithuania and Poland. Sipri researcher Tytti Erästö pointed to Finland and Sweden, historically non-aligned advocates of disarmament, who are now actively participating in NATO nuclear policy and exercises simulating nuclear weapons use.

Making national defence and security strategies dependent — or more dependent — on nuclear weapons could considerably increase nuclear risks.

Sipri Director Karim Haggag warned that the dangers are growing because of technological advances, the collapse of arms control and heightened geopolitical tensions. The institute expects the decades-long trend of declining global stockpiles to reverse in the coming years as dismantlement slows and the deployment of new weapons accelerates.