The Stockholm International Peace Research Institute (SIPRI) launches its annual assessment of the state of armaments, disarmament and international security

Washington, D.C. – June 16, 2025 – Nuclear weapons researchers at the Federation of American Scientists (FAS) contributed to the Stockholm International Peace Research Institute (SIPRI)’s annual Yearbook, released today. Key findings of SIPRI Yearbook 2025 are that a dangerous new nuclear arms race is emerging at a time when arms control regimes are severely weakened.

“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.”

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. 

Of the total global inventory of an estimated 12,241 warheads in January 2025, about 9614 were in military stockpiles for potential use (see the table below). 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. 

Russia and the USA together possess around 90 per cent of all nuclear weapons. The sizes of their respective military stockpiles (i.e. useable warheads) seem to have stayed relatively stable in 2024 but both states are implementing extensive modernization programmes that could increase the size and diversity of their arsenals in the future. If no new agreement is reached to cap their stockpiles, the number of warheads they deploy on strategic missiles seems likely to increase after the bilateral 2010 Treaty on Measures for the Further Reduction and Limitation of Strategic Offensive Arms (New START) expires in February 2026. 

The USA’s comprehensive nuclear modernization programme is progressing but in 2024 faced planning and funding challenges that could delay and significantly increase the cost of the new strategic arsenal. Moreover, the addition of new non-strategic nuclear weapons to the US arsenal will place further stress on the modernization programme. 

Russia’s nuclear modernization programme is also facing challenges that in 2024 included a test  failure and the further delay of the new Sarmat intercontinental ballistic missile (ICBM) and slower  than expected upgrades of other systems. Furthermore, an increase in Russia’s non-strategic nuclear warheads predicted by the USA in 2020 has so far not materialized. 

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ABOUT FAS

The Federation of American Scientists (FAS) works to advance progress on a broad suite of contemporary issues where science, technology, and innovation policy can deliver transformative impact, and seeks to ensure that scientific and technical expertise have a seat at the policymaking table. Established in 1945 by scientists in response to the atomic bomb, FAS continues to bring scientific rigor and analysis to address contemporary challenges. More information about FAS work at fas.org.

Goodbye, decades of nuclear weapon reduction?

Hans Kristensen and Matt Korda with the FAS Nuclear Information Project write in the new SIPRI Yearbook, released today, that the world’s nuclear arsenals are on the rise, massive modernization programs are underway, and nuclear weapons are becoming more prominent in military strategies and rhetoric.

It is clear that the gradual reductions in nuclear stockpiles that characterized the post-Cold War period is over, and that the world is sliding back into nuclear competition and––in some cases––an arms race.

The development is in stark contrast to the promises made by many nuclear-armed states to reduce nuclear risks and seek a world without nuclear weapons.

The SIPRI Yearbook is published by the Stockholm International Peace Research Institute (SIPRI) and is one of the most widely cited sources of information on nuclear weapons. The nuclear data is derived from the research and analysis the Nuclear Information Project uses to produce the Status of World Nuclear Forces on the FAS website.

The SIPRI chapter describes the nuclear weapon modernization programs underway in each nuclear-armed state and provides estimates for how many nuclear warheads each country possesses. Combined, the research team, which includes Kristensen, Korda, Eliana Johns, and Mackenzie Knight, estimates that the combined global inventory of nuclear warheads is approximately 12,120. Of these, around 3,900 are estimated to be deployed on missiles and aircraft (2,100 of which are on high operational alert on ballistic missiles). Thousands of warheads (some 5,680) are stored in special depots for deployment if necessary. The remaining 2,540 warheads or so are retired and awaiting dismantlement. 

Moreover, with the increased nuclear competition, the research team reports that government transparency of nuclear forces is decreasing.

Read it here: SIPRI Yearbook 2024 nuke chapter

This research was carried out with generous contributions from the Joseph Rowntree Charitable Trust, Longview Philanthropy, New-Land Foundation, Ploughshares Fund, the Prospect Hill Foundation, and individual donors.

FAS’s Nuclear Information Project estimates that the combined global inventory of nuclear warheads is approximately 12,120

Washington, DC – June 17, 2024 – The Federation of American Scientists’ nuclear weapons researchers Hans Kristensen and Matt Korda with the Nuclear Information Project write in the new SIPRI Yearbook, released today, that the world’s nuclear arsenals are on the rise, and massive modernization programs are underway.

“China is expanding its nuclear arsenal faster than any other country,” 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). “But in nearly all of the nuclear-armed states, there are either plans or a significant push to increase nuclear forces.”

“We are entering a new period in the post-Cold War era as nuclear stockpiles increase and nuclear transparency decreases. It is, therefore, extremely important for independent researchers to inject factual data into the debate,” says Matt Korda, Associate Researcher in the SIPRI Weapons of Mass Destruction Programme and Senior Research Fellow at FAS. 

Kristensen and Korda are leading researchers on the global stockpile of nuclear weapons. Along with their colleagues Eliana Johns and Mackenzie Knight, the Nuclear Information Project team at FAS produces the Nuclear Notebook, a bi-monthly report published in the Bulletin of Atomic Scientists detailing current estimates of nuclear weapon stockpiles. This work plays an increasingly important role as government transparency about nuclear forces continues to decline around the globe. Ongoing reports, archives, and other materials are available at fas.org.

The first edition of the SIPRI Yearbook was released in 1969, with the aim of producing “a factual and balanced account of a controversial subject-the arms race and attempts to stop it.” Interested parties may download excerpts from the latest Yearbook in several languages here, or purchase the report in full.

Read a summary of SIPRI findings by FAS Nuclear Information Project researcher Eliana Johns here.

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ABOUT FAS

The Federation of American Scientists (FAS) works to advance progress on a broad suite of contemporary issues where science, technology, and innovation policy can deliver dramatic progress, and seeks to ensure that scientific and technical expertise have a seat at the policymaking table. Established in 1945 by scientists in response to the atomic bomb, FAS continues to work on behalf of a safer, more equitable, and more peaceful world. More information at fas.org.