SIPRI Director Dan Smith said, "With all these new technologies and variables in play, ‘the idea of who is ahead in the arms race will be even more elusive and intangible than it was last time round. In this context, the old largely numerical formulas of arms control will no longer suffice."

The 56th edition of the SIPRI Yearbook analyses the continuing deterioration of global security over the past year.

The wars in Ukraine, Gaza and elsewhere continued, exacerbating geopolitical divisions, besides their terrible human costs.

Furthermore, the election of Donald Trump has created additional uncertainty—in Europe but also further afield—about the future direction of US foreign policy and the reliability of the USA as an ally, a donor or an economic partner.

In addition to the usual detailed coverage of nuclear arms control, disarmament and non-proliferation issues, the SIPRI Yearbook presents data and analysis on developments in world military expenditure, international arms transfers, arms production, multilateral peace operations, armed conflicts, cyber and digital threats, space security governance and more.

World’s Nuclear Arsenals Being Enlarged And Upgraded

Nearly all of the nine nuclear-armed states—the United States, Russia, the United Kingdom, France, China, India, Pakistan, the Democratic People’s Republic of Korea (North Korea) and Israel—continued intensive nuclear modernization programmes in 2024, upgrading existing weapons and adding newer versions.

SIPRI said of the total global inventory of an estimated 12 241 warheads in January 2025, about 9614 were in military stockpiles for potential use.

An estimated 3912 of those warheads were deployed with missiles and aircraft and the rest were in central storage.

Around 2100 of the deployed warheads were kept in a state of high operational alert on ballistic missiles.

Nearly all of these warheads belonged to Russia or the USA, but China may now keep some warheads on missiles during peacetime.

Since the end of the cold war, the gradual dismantlement of retired warheads by Russia and the USA has normally outstripped the deployment of new warheads, resulting in an overall year-on-year decrease in the global inventory of nuclear weapons.

This trend is likely to be reversed in the coming years, as the pace of dismantlement is slowing, while the deployment of new nuclear weapons is accelerating.

"The era of reductions in the number of nuclear weapons in the world, which had lasted since the end of the cold war, is coming to an end," said Hans M. Kristensen, Associate Senior Fellow with SIPRI’s Weapons of Mass Destruction Programme and Director of the Nuclear Information Project at the Federation of American Scientists (FAS).

"Instead, we see a clear trend of growing nuclear arsenals, sharpened nuclear rhetoric and the abandonment of arms control agreements," Kristensen said.

SIPRI estimates that China now has at least 600 nuclear warheads.

China’s nuclear arsenal is growing faster than any other country’s, by about 100 new warheads a year since 2023.

"By January 2025, China had completed or was close to completing around 350 new ICBM silos in three large desert fields in the north of the country and three mountainous areas in the east," SIPRI said.

Depending on how it decides to structure its forces, China could potentially have at least as many ICBMs as either Russia or the USA by the turn of the decade, SIPRI said.

"Yet even if China reaches the maximum projected number of 1500 warheads by 2035, that will still amount to only about one third of each of the current Russian and US nuclear stockpiles," the institute said.

India's Position

Speaking on India's position, SIPRI said it is believed to have once again slightly expanded its nuclear arsenal in 2024 and continued to develop new types of nuclear delivery system.

"India’s new ‘canisterized’ missiles, which can be transported with mated warheads, may be capable of carrying nuclear warheads during peacetime, and possibly even multiple warheads on each missile, once they become operational," the institute said.

SIPRI said Pakistan also continued to develop new delivery systems and accumulate fissile material in 2024, suggesting that its nuclear arsenal might expand over the coming decade.