As the United States overhauls nearly every element of its strategic nuclear forces, artificial intelligence is set to play a larger role—initially in early‑warning sensors and decision‑support tools, and likely in other mission areas. Improved detection could strengthen deterrence, but only if accompanying hazards—automation bias, model hallucinations, exploitable software vulnerabilities, and the risk of eroding assured second‑strike capability—are well managed. 

To ensure responsible AI integration, the Office of the Assistant Secretary of Defense for Nuclear Deterrence, Chemical, and Biological Defense Policy and Programs (OASD (ND-CBD)), the U.S. Strategic Command (STRATCOM), the Defense Advanced Research Projects Agency (DARPA), the Office of the Undersecretary of Defense for Policy (OUSD(P)), and the National Nuclear Security Administration (NNSA), should jointly develop a standardized AI risk-assessment framework guidance document, with implementation led by the Department of Defense’s Chief Digital and Artificial Intelligence Office (CDAO) and STRATCOM. Furthermore, DARPA and CDAO should join the Nuclear Weapons Council to ensure AI-related risks are systematically evaluated alongside traditional nuclear modernization decisions. 

Challenge and Opportunity 

The United States is replacing or modernizing nearly every component of its strategic nuclear forces, estimated to cost at least $1.7 trillion over the next 30 years. This includes its:

• Intercontinental ballistic missiles (ICBMs)
• Ballistic missile submarines and their submarine-launched ballistic missiles (SLBMs) 
• Strategic bombers, cruise missiles, and gravity bombs
• Nuclear warhead production and plutonium pit fabrication facilities 

Simultaneously, artificial intelligence (AI) capabilities are rapidly advancing and being applied across the national security enterprise, including nuclear weapons stockpile stewardship and some components of command, control, and communications (NC3) systems, which encompass early warning, decision-making, and force deployment components.

The NNSA, responsible for stockpile stewardship, is increasingly integrating AI into its work. This includes using AI for advanced modeling and simulation of nuclear warheads. For example, by creating a digital twin of existing weapons systems to analyze aging and performance issues, as well as using AI to accelerate the lifecycle of nuclear weapons development. Furthermore, NNSA is leading some aspects of the safety testing and systematic evaluations of frontier AI models on behalf of the U.S. government, with a specific focus on assessing nuclear and radiological risk.

Within the NC3 architecture, a complex “system of systems” with over 200 components, simpler forms of AI are already being used in areas including early‑warning sensors, and may be applied to  decision‑support tools and other subsystems as confidence and capability grow. General Anthony J. Cotton—who leads STRATCOM, the combatant command that directs America’s global nuclear forces and their command‑and‑control network—told a 2024 conference that STRATCOM is “exploring all possible technologies, techniques, and methods” to modernize NC3. Advanced AI and data‑analytics tools, he said, can sharpen decision‑making, fuse nuclear and conventional operations, speed data‑sharing with allies, and thus strengthen deterrence. General Cotton added that research must also map the cascading risks, emergent behaviors, and unintended pathways that AI could introduce into nuclear decision processes.

Thus, from stockpile stewardship to NC3 systems, AI is likely to be integrated across multiple nuclear capabilities, some potentially stabilizing, others potentially highly destabilizing. For example, on the stabilizing effects, AI could enhance early warning systems by processing large volumes of satellite, radar, and other signals intelligence, thus providing more time to decision-makers. On the destabilizing side, the ability for AI to detect or track other countries’ nuclear forces could be destabilizing, triggering an expansionary arms race if countries doubt the credibility of their second-strike capability. Furthermore, countries may misinterpret each other’s nuclear deterrence doctrines or have no means of verification of human control of their nuclear weapons.

While several public research reports have been conducted on how AI integration into NC3 could upset the balance of strategic stability, less research has focused on the fundamental challenges with AI systems themselves that must be accounted for in any risk framework. Per the National Institute of Standards and Technology’s (NIST) AI Risk Management Framework, several fundamental AI challenges at a technical level must be accounted for in the integration of AI into stockpile stewardship and NC3.

Not all AI applications within the nuclear enterprise carry the same level of risk. For example, using AI to model warhead aging in stockpile stewardship is largely internal to the Department of Energy (DOE) and involves less operational risk. Despite lower risk, there is still potential for an insufficiently secure model to lead to leaked technical data about nuclear weapons. 

However, integrating AI into decision support systems or early warning functions within NC3 introduces significantly higher stakes. These systems require time-sensitive, high-consequence judgments, and AI integration in this context raises serious concerns about issues including confabulations, human-AI interactions, and information security: 

• Confabulations: A phenomenon in which generative AI systems (GAI) systems generate and confidently present erroneous or false content in response to user inputs, or
  prompts. These phenomena are colloquially also referred to as “hallucinations” or “fabrications”, and could have particularly dangerous consequences in high-stakes settings. 

• Human-AI Interactions: Due to the complexity and human-like nature of GAI technology, humans may over-rely on GAI systems or may unjustifiably perceive GAI content to be of higher quality than that produced by other sources. This phenomenon is an example of automation bias or excessive deference to automated systems. This deference can lead to a shift from a human making the final decision (“human in the loop”), to a human merely observing AI generated decisions (“human on the loop”). Automation bias therefore risks exacerbating other risks of GAI systems as it can lead to humans maintaining insufficient oversight.

• Information Security: AI expands the cyberattack surface of NC3. Poisoned AI training data and tampered code can embed backdoors, and, once deployed, prompt‑injection or adversarial examples can hijack AI decision tools, distort early‑warning analytics, or leak secret data. The opacity of large AI models can let these exploits spread unnoticed, and as models become more complex, they will be harder to debug.

This is not an exhaustive list of issues with AI systems, however it highlights several key areas that must be managed. A risk framework must account for these distinctions and apply stricter oversight where system failure could have direct consequences for escalation or deterrence credibility. Without such a framework, it will be challenging to harness the benefits AI has to offer.

Plan of Action 

Recommendation 1. OASD (ND-CBD),  STRATCOM, DARPA, OUSD(P), and NNSA, should develop a standardized risk assessment framework guidance document to evaluate the integration of artificial intelligence into nuclear stockpile stewardship and NC3 systems. 

This framework would enable systematic evaluation of risks, including confabulations, human-AI configuration, and information security, across modernization efforts. The framework could assess the extent to which an AI model is prone to confabulations, involving performance evaluations (or “benchmarking”) under a wide range of realistic conditions. While there are public measurements for confabulations, it is essential to evaluate AI systems on data relevant to the deployment circumstances, which could involve highly sensitive military information.  

Additionally, the framework could assess human-AI configuration with specific focus on risks from automation bias and the degree of human oversight. For these tests, it is important to put the AI systems in contact with human operators in situations that are as close to real deployment as possible, for example when operators are tired, distracted, or under pressure. 

Finally, the framework could include assessments of information security under extreme conditions. This should include simulating comprehensive adversarial attacks (or “red-teaming”) to understand how the AI system and its human operators behave when subject to a range of known attacks on AI systems.

NNSA should be included in this development due to their mission ownership of stockpile stewardship and nuclear safety, and leadership in advanced modeling and simulation capabilities. DARPA should be included due to its role as the cutting edge research and development agency, extensive experience in AI red-teaming, and understanding of the AI vulnerabilities landscape. STRATCOM must be included as the operational commander of NC3 systems, to ensure the framework accounts for real-word needs and escalation risks. OASD (ND-CBD) should be involved given the office’s responsibilities to oversee nuclear modernization and coordinate across the interagency. The OUSD (P) should be included to provide strategic oversight and ensure the risk assessment aligns with broader defense policy objectives and international commitments.

Recommendation 2. CDAO should implement the Risk Assessment Framework with STRATCOM

While NNSA, DARPA, OASD (ND-CBD) and STRATCOM can jointly create the risk assessment framework, CDAO and STRATCOM should serve as the implementation leads for utilizing the framework. Given that the CDAO is already responsible for AI assurance, testing and evaluation, and algorithmic oversight, they would be well-positioned to work with relevant stakeholders to support implementation of the technical assessment. STRATCOM would have the strongest understanding of operational contexts with which to apply the framework. NNSA and DARPA therefore could advise on technical underpinnings with regards to AI of the framework, while the CDAO would prioritize operational governance and compliance, ensuring that there are clear risk assessments completed and understood when considering integration of AI into nuclear-related defense systems.

Recommendation 3. DARPA and CDAO should join the Nuclear Weapons Council 

Given their roles in the creation and implementation of the AI risk assessment framework, stakeholders from both DARPA and the CDAO should be incorporated into the Nuclear Weapons Council (NWC), either as full members or attendees to a subcommittee. As the NWC is the interagency body the DOE and the DoD responsible for sustaining and modernizing the U.S. nuclear deterrent, the NWC is responsible for endorsing military requirements, approving trade-offs, and ensuring alignment between DoD delivery systems and NNSA weapons. 

As AI capabilities become increasingly embedded in nuclear weapons stewardship, NC3 systems, and broader force modernization, the NWC must be equipped to evaluate associated risks and technological implications. Currently, the NWC is composed of senior officials from the Department of Defense, the Joint Chiefs of Staff, and the Department of Energy, including the NNSA. While these entities bring deep domain expertise in nuclear policy, military operations, and weapons production, the Council lacks additional representation focused on AI.

DARPA’s inclusion would ensure that early-stage technology developments and red-teaming insights are considered upstream in decision-making. Likewise, CDAO’s presence would provide continuity in AI assurance, testing, and digital system governance across operational defense components. Their participation would enhance the Council’s ability to address new categories of risk, such as model confabulation, automation bias, and adversarial manipulation of AI systems, that are not traditionally covered by existing nuclear stakeholders. By incorporating DARPA and CDAO, the NWC would be better positioned to make informed decisions that reflect both traditional nuclear considerations and the rapidly evolving technological landscape that increasingly shapes them.

Conclusion 

While AI is likely to be integrated into components of the U.S. nuclear enterprise, without a standardized initial approach to assessing and managing AI-specific risk, including confabulations, automation bias, and novel cybersecurity threats, this integration could undermine an effective deterrent. A risk assessment framework coordinated by OASD (ND-CBD), with STRATCOM, NNSA and DARPA, and implemented with support of the CDAO, could provide a starting point for NWC decisions and assessments of the alignment between DoD delivery system needs, the NNSA stockpile, and NC3 systems.

This memo was written by an AI Safety Policy Entrepreneurship Fellow over the course of a six-month, part-time program that supports individuals in advancing their policy ideas into practice. You can read more policy memos and learn about Policy Entrepreneurship Fellows here.

Frequently Asked Questions

Does the NWC have the authority to create a new subcommittee including DARPA and the CDAO?

Yes, NWC subordinate organizations or subcommittees are not codified in Title 10 USC §179, so the NWC has the flexibility to create, merge, or abolish organizations and subcommittees as needed.

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Are there existing regulations that the United States has declared with respect to AI integration into NC3?

Section 1638 of the FY2025 National Defense Authorization Act established a Statement of Policy emphasizing that any use of AI in support of strategic deterrence should not compromise, “the principle of requiring positive human actions in execution of decisions by the President with respect to the employment of nuclear weapons.” However, as this memo describes, AI presents further challenges outside of solely keeping a human in the loop in terms of decision-making.

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Washington, D.C. – May 6, 2025 – The Federation of American Scientists (FAS) today released “Nuclear Notebook: Russian Nuclear Weapons 2025,” its authoritative annual survey of Russia’s nuclear weapons arsenal. The FAS Nuclear Notebook is considered the most reliable public source for information on global nuclear arsenals for all nine nuclear-armed states. FAS has played a critical role for almost 80 years to increase transparency and accountability over the world’s nuclear arsenals and to support policies that reduce the numbers and risks of their use.

This year’s report, published in the Bulletin of the Atomic Scientists and by Taylor & Francis and available in full here, discusses the following takeaways:

• Russia currently maintains nearly 5,460 nuclear warheads, with an estimated 1,718 deployed. This represents a slight decrease in total warheads from previous years but still positions Russia as the world’s largest nuclear power alongside the United States.
• Russia continues to modernize its nuclear triad, replacing Soviet-era weapons with newer types, but modernization of ICBMs and strategic bombers has been slow. The country’s efforts to develop the advanced Sarmat (RS-28 or SS-29) ICBM and the next-generation strategic bomber, PAK DA, have faced delays and setbacks.
• The submarine-based nuclear force continues its modernization with Borei-class submarines replacing older types. A portion of Russian ballistic missile submarines are at sea at any given time on strategic deterrent patrols. Significant nuclear warhead and missile storage upgrades are underway at the Pacific and Northern fleet bases.
• Russia continues modernizing and emphasizing its nonstrategic  nuclear forces. This includes land- and sea-based dual-capable missiles and tactical aircraft. Despite modernization of launchers, the number of warheads assigned to those launchers has remained relatively stable. Russia held several high-profile exercises with its nonstrategic forces in 2024, and the authors describe upgrades to a suspected nuclear storage depot in Belarus.
• Russia has maintained its policy of nuclear deterrence, emphasizing the strategic importance of its nuclear arsenal in its military doctrine. Updates to public policy documents describe a broader range of scenarios for potential use of nuclear weapons but it is unknown to what extent this is reflected in changes to military plans.
  

FAS Nuclear Experts and Previous Issues of Nuclear Notebook

The FAS Nuclear Notebook, co-authored by Hans M. Kristensen, Matt Korda, Eliana Johns, and Mackenzie Knight, is published bi-monthly in the Bulletin of the Atomic Scientists. The first Nuclear Notebook was published in 1987. FAS, formed in 1945 by the scientists who developed the first U.S. nuclear weapon, has worked since to increase nuclear transparency, reduce nuclear risks, and advocate for responsible reductions of nuclear arsenal and their role.

This latest issue on Russia’s nuclear weapons comes after the release of Nuclear Notebook: Chinese Nuclear Weapons 2025 and will be followed in June by Nuclear Notebook: French Nuclear Weapons 2025. More research available at FAS’s Nuclear Information Project.


The Federation of American Scientists’ work on nuclear transparency would not be possible without generous support from the Carnegie Corporation of New York, the Joseph Rowntree Charitable Trust, the Jubitz Family Foundation, the New-Land Foundation, Ploughshares, the Prospect Hill Foundation, and individual donors.

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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.

In 2014, my colleagues  at the Monterey Institute for International Studies and I authored a study called The Trillion Dollar Nuclear Triad. This report laid out comprehensively, for the first time, that the recently launched US nuclear modernization program–including building new nuclear-armed submarines, bombers, and long-range missiles as well as new nuclear weapons–would likely cost over $1 trillion during its 30-year time scale. Until then, no one had even an estimate for how much these programs would cost over their lifetimes. At the time, my co-authors and I were criticized by advocates for the nuclear modernization program as alarmist and accused of actively seeking to inflate estimates to undermine political support for these programs. Overall, proponents argued that these programs were necessary and that the cost was a mere fraction of the Pentagon’s overall budget, historically low when compared to the nuclear modernization of the 1970s and 1980s. What was originally described merely as a bow wave of costs has become a tsunami.

On April 25, the Congressional Budget Office released its latest estimate that costs of maintaining the current nuclear arsenal and modernizing the entire program would cost nearly $1 trillion over the next 10 years alone.  As was once said, there are lies, damn lies, and statistics. This is not an argument about statistics but about absolute numbers. By any measure, $1 trillion is an enormous amount of money to spend in 10 years, and any other U.S. Government or private effort on this scale would receive intense scrutiny and attention–in fact, the Sentinel ICBM modernization most recently triggered a critical breach of the Nunn McCurdy act in 2024. Moreover, if the nuclear budget is going to average 10% from the estimated $1 trillion annual defense budget for the next decade, the nuclear program is now eating the defense budget alive.

For those who may doubt whether oversight is necessary, one only needs to look at one of the more visible elements of the nuclear modernization program–the effort to replace the Minuteman III intercontinental ballistic missile program. When we did our original estimate in 2014, there was no estimate for the cost of replacing the MMIII. We noted that past efforts to build comparable long-range missile systems were complex, expensive, and prone to large cost overruns. The example we cited was the “Evolved Expendable Launch Vehicle, which involved the purchase of 150 space launch vehicles based on existing technologies. Originally slated to cost $30 billion, program costs now exceed $70 billion.”

The sole recommendation of this 2014 report was that the USG and Department of Defense in particular needs to create a stand alone nuclear budget to understand the complex nature of these programs and their costs, and keep them on budget and under control. While we did not push the recommendation in the report, we strongly suggested overall that the program was unlikely to meet schedule and cost milestones because it was going to put the constrained U.S. defense industrial capacity under stress and it would be better to stagger these complex multi-decade and multi-billion dollar programs.Ten years later, this recommendation is still needed.

To push these programs through and dismiss alternatives, the military and defense contractors and defense hawks in Congress argued the sky was falling, that Russia and China were modernizing, that nuclear war would be more expensive, so there was no margin for error or delay to consider alternatives. Ironically, the mismanagement of the modernization program now threatens to produce the very delay they were warning against.

In all of these areas, our report was not only rebuffed by advocates for the nuclear modernization program, but our recommendations were ignored. And over time, the consequences of plowing ahead with these programs despite predicted problems have come to pass. The MMIII replacement program, now dubbed Sentinel, was originally estimated to cost $62 billion. That program is now slated to cost $126 billion in the next 10 years alone, and over $140 billion in total. Those costs can also be expected to keep rising due to ongoing delays in the program. This program bypassed the normal programmatic reviews and procurement milestones, and was rushed to a single source contract during President Trump’s first term, with predictably bad results. It now seems likely that the Air Force will have to extend the life of the MMIII missile through 2050–something supporters of the new ICBM have argued would be impossible in both 2021 and 2023.

There is still no comprehensive budget from DOD laying out their costs or predicting the full cost of implementing the current U.S. nuclear weapons modernization program. This is akin to agreeing to buying a house without knowing the sales price, the mortgage rate, or the monthly payment. Yes, you need to live somewhere, but in an era where critical U.S. programs for defense, science, climate, health and international programs and even nuclear weapons security and safety are being cut, it is nonsensical that these programs continue without adequate oversight and knowledge of their true costs.

Whether the U.S. can afford these programs is a reasonable question. Knowing how much these new systems will cost, it is appropriate to ask: if the Pentagon can not produce even a budget on costs, how can they be expected to oversee and deliver what their advocates claim are critical national security programs? The inadequate oversight, cost management and even basic program accountability will result, as we predicted in 2014, “disarmament by default”,  an unsustainable and dangerous way to manage U.S. national security.

The United States Air Force has forward deployed about one-third of its B-2 stealth bombers to Diego Garcia, or about half the B-2s considered fully operational at any given time. A Planet Labs satellite image taken earlier today shows six of the characteristic bombers on the apron alongside six refueling tankers.

A Planet Lab satellite image from earlier today shows six B-2 bombers at Diego Garcia in the Indian Ocean.

The current deployment of at least six B-2s to Diego Garcia is unusually large and exceeds the number of climate tents at the base designed to protect the sensitive surface of the bombers. The current deployment began a week ago.

US bombers regularly deploy on so-called Bomber Task Force missions to bases overseas or long-range exercise flights. That has included occasional B-2 bombers to Diego Garcia before (one in 2024 (hot pit refuel) and three in 2020), but the visits are rare and B-2s are designed to carry out global strike missions without having to deploy to forward locations. A B-2 strike against the Houthis in November 2024, for example, was flown directly from Whiteman AFB.

B-52 bombers have also deployed to Diego Garcia, including in 2024.

During 2024, U.S. bombers (B-1, B-2, and B-52) were deployed about 60 percent of the year to a theater or providing continental U.S. (CONUS) -to-CONUS flights in support of theaters or in support of U.S. Strategic Command and the Chairman of Joint Chiefs of Staff,” according to the U.S. Air Force.

During the past week the number of bombers visible at the base has fluctuated from none to two or four, indicating that the remaining bombers are either inside the climate tents or airborne on a training or perhaps bombing mission against Houthis forces. The U.S. Air Force operates a fleet of 20 B-2s. Of these, one is a test aircraft, and normally only 10-12 are considered fully operational with the rest undergoing repairs and routine maintenance. During the Spirit Vigilance exercise in April 2024, for example, the 509^th and 131^st bomber wings at Whiteman AFB in Missouri conducted a “mass fly-off” of all the operational B-2 bombers.

The B-2s deployed at Diego Garcia constitute about half of the operational B-2s, seen here in a “mass fly-off” exercise at Whiteman AFB in 2024.

That means about half of the entire operational B-2 force is currently forward deployed at Diego Garcia. The large deployment to Diego Garcia is part of evolving B-2 operations in the Western Pacific and Indian Ocean that also involve more deployments to Australia.

The B-2 bombers are dual-capable, which means they can deliver both conventional and nuclear weapons. Conventional weapons include precision guided bombs and cruise missiles as well as heavy earth penetrators. Nuclear weapons include the B61-12 guided bombs and the B61-11 nuclear earth-penetrator (the B61-7 has been replaced by the B61-12 and the B83-1 is no longer operational). There are no nuclear weapons on this Diego Garcia mission.

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Background: United States Nuclear Weapons, 2025

Washington, D.C. – March 12, 2025 – The Federation of American Scientists (FAS) today released “Nuclear Notebook: China” – its authoritative annual survey of China’s nuclear weapons arsenal. The FAS Nuclear Notebook is considered the most reliable public source for information on global nuclear arsenals for all nine nuclear-armed states. FAS has played a critical role for almost 80 years to increase transparency and accountability over the world’s nuclear arsenals and to support policies that reduce the numbers and risks of their use.

This year’s report, published in the Bulletin of Atomic Scientists, shows the following nuclear trends:

• The total number of Chinese nuclear warheads is now estimated to include approximately 600 warheads. The vast majority of these are in storage and a small number—perhaps 24—are deployed. 

• China is NOT a nuclear “peer” of the United States, as some contend. China’s total number of approximately 600 warheads constitutes only a small portion of the United States’ estimated stockpile of 3,700 warheads.  While the United States has a fully established triad of strategic forces, China is still working to develop a nuclear triad; the submarine-based leg has significantly less capability, and the bomber leg is far less capable than the United States.
  
• China continues to see their land-based intercontinental ballistic missiles (ICBMs) as their most reliable and survivable nuclear force. China continues to prioritize its land-based force and increase its role in both number and capability. China has completed construction of its three new ICBM silo fields, one of which was publicly disclosed by FAS in 2021.  We estimate that around 30 silos have been loaded. China has also increased the number of road-mobile ICBM bases.
  
• China is continuing to develop its relatively small ballistic missile submarines (SSBN) force through improved missiles and a follow-on SSBN class. Production of the new “Type 096” SSBN has been delayed. We estimate that Chinese SSBNs are now conducting continuous patrols with nuclear weapons on board. However, Chinese SSBNs cannot target continental United States from their operating areas.
  
• Development of a viable nuclear bomber force is still in its early stages. Only one base has been established at Neixiang for the new H-6N bomber. The H-20 replacement bomber appears to be delayed.  

FAS Nuclear Experts and Previous Issues of Nuclear Notebook

The FAS Nuclear Notebook, co-authored by Hans M. Kristensen, Matt Korda, Eliana Johns, and Mackenzie Knight, is published bi-monthly in the Bulletin of the Atomic Scientists. The joint publication began in 1987. FAS, formed in 1945 by the scientists who developed the nuclear weapon, has worked since to increase nuclear transparency, reduce nuclear risks, and advocate for responsible reductions of nuclear arsenal and their role.

This latest issue on the United State’s nuclear weapons comes after the release of Nuclear Notebook: United States on America’s nuclear arsenal. More research available at FAS’s Nuclear Information Project.

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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.

Washington, D.C. – March 7, 2025 – The Federation of American Scientists (FAS) is pleased to welcome Dr. Yong-Bee Lim as the new Associate Director of Global Risk. In this role, Dr. Lim will help develop, organize, and implement FAS’s growing contribution in the area of catastrophic risk prevention, including on core areas of nuclear weapons, AI and national security, space and other emerging technologies.  

“The role of informed, credible and engaging organizations in support of sound public policy is more important than ever” said Jon Wolfsthal, FAS Director of Global Risk. “Yong-Bee embodies what it means to be an effective policy entrepreneur and to make meaningful contributions to US and global security. We are really excited that he is now part of the FAS team.”

Dr. Lim is a recognized expert in biosecurity, emerging technologies, and converging risks through his former roles as Deputy Director of both the the Converging Risks Lab and the Janne E. Nolan Center at the Council on Strategic Risks, his research and leadership roles in academia, and through his work at key agencies (DoD, HHS/ASPR, and DoE) in the United States. He completed his Ph.D. in Biodefense from George Mason University’s Biodefense program, where he conducted critical work on understanding the safety, security, and cultural dimensions of the U.S.-based Do-It-Yourself Biology (DIYBio) community. His recent accolades include being in the inaugural fellowship class of the Editorial Fellows program at the Bulletin of the Atomic Scientists and his selection and involvement in the Emerging Leaders in Biosecurity Initiative hosted by the Johns Hopkins Center for Health Security. 

“As emerging capabilities change the very contours of safety, security, and innovation, FAS has positioned itself to both highlight the global opportunities we must seize and address the global risks we must mitigate,” Lim said. “Founded in 1945, FAS continues to display thought leadership and impact because it has not forgotten its core mission: to ensure that scientific and technical expertise continue to have a seat at the policymaking table. I am honored to be part of an organization with a legacy and mission like FAS.”

ABOUT FAS

The Federation of American Scientists (FAS) works to advance progress on a broad suite of 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 and Global Risk, here.

Between 2006 and 2015, the United Kingdom repeatedly and publicly announced its intentions to decrease the size of its nuclear weapons stockpile, most recently committing to at most 180 weapons by the mid-2020s. As the years went by, non-government policy experts and nuke watchers assumed that the UK Government was making good on its word and that the UK nuclear arsenal would continue to gradually reduce. In reality, the United Kingdom is thought to have maintained a nuclear stockpile of approximately 225 weapons, and, in a surprise move in 2021, the United Kingdom declared that it would extend the ceiling of its “overall nuclear weapon stockpile” to no more than 260 weapons. This constituted an abrupt about-face from its previous commitments and trajectory. 

However, the infrastructure underpinning the sustainability of the United Kingdom’s nuclear weapons and their modernization has experienced significant budgetary and scheduling challenges. Furthermore, the UK has dramatically reduced the public transparency of its nuclear forces, making it increasingly difficult to understand and debate the true scope of these challenges.

The UK’s Nuclear Warhead Modernization

Announced in 2005, the Atomic Weapons Establishment’s (AWE) Nuclear Warhead Capability Sustainment Programme (NWCSP) was an initiative to deliver infrastructure and technology to sustain the United Kingdom’s current stockpile and underpin its warhead replacement program. Each of these main infrastructure and technology projects is named after a constellation: Project Orion for a high-power research laser that began operations in 2013, Project Leo for a small parts manufacturing facility, Project Pegasus for the manufacturing of uranium components effort, and so on. Several of these projects under the NWCSP related to techniques used for nuclear weapons development in place of explosive testing. Part of the NWCSP mission also involved refurbishing the United Kingdom’s current warheads for integration with the U.S.-supplied, upgraded Mk4A aeroshell, which was completed in 2023. The NWCSP was scheduled to run from April 2008 until April 2025 and was removed from the MOD Government Major Projects Portfolio data starting in 2022, indicating it could have been downsized from a large-scale development initiative.

In February 2020, the UK defence secretary announced a new warhead program—the A21/Mk7/ Astraea. This new warhead is currently in the concept stage but is planned to eventually replace the Mk4A/Holbrook beginning in the late 2030s. As was the case with the previous version, the A21/Mk7 Astraea design and production will have a “very close connection” to the future US W93/Mk7.

In 2023, the MOD confirmed that £127 million had been spent on the A21 Astraea warhead replacement program as of March 2022. The total cost of the replacement program has not been released, given it is still in the early stages. However, even if cumulative costs are released, individual costs associated with the warhead modernization program will be challenging to identify due to changes in UK budgetary reporting practices. In 2023, nuclear-related programs and expenditures—including the AWE and the NWCSP—were compiled into one heading under Defence Nuclear Enterprise (DNE), which appears as a single line item in the departmental estimates. This makes it impossible to see the direct in-service costs associated with the individual programs. DNE funding was also “ringfenced” within the MOD budget to protect it against spending cuts. 

The UK’s declaration that its stockpile ceiling will be raised to 260 raises several questions. In the early- to mid-2000s, the United Kingdom possessed a stockpile of roughly 280 warheads, but in 2010 announced it would reduce this level to “no more than 225 warheads.” To be able to increase this level to up to 260 warheads, as announced by the UK government in 2021, it seems some of the retired warheads—or components from them—must have been retained in some form. The United Kingdom appears to use the term “stockpile” to describe operational, deployed, and retired weapons. The timeline for potentially increasing the stockpile to up to 260 is not known, but if it is a relatively short timeline, it would seem to require reconstituting some retired warheads. If it is a longer timeline, it could potentially involve increasing the number of A21 Astraea warheads in the future. Of the “no more than 225” warhead stockpile level, the United Kingdom has previously explained that 120 warheads would be operationally available, of which 40 would be deployed on the single ballistic missile submarine (SSBN) on patrol at all times. The reason for increasing the stockpile to up to 260 warheads appears to be derived from an interest in increasing the number of “operationally available” warheads to be able to deploy a full warhead load on the SSBN fleet—something the recent warhead level did not allow.

Critical Infrastructure 

Any warhead design, manufacturing, and testing occurs at the AWE site at Aldermaston while the warheads are assembled, maintained, and decommissioned at AWE Burghfield. These two sites are critical to maintaining the United Kingdom’s existing stockpile and will play a significant role in the new warhead replacement program. 

Upgrades at AWE Burghfield

Project MENSA—one of the infrastructure programs under the NWCSP—aims to consolidate existing nuclear warhead assembly and disassembly operations into a single building located in the center of the AWE Burghfield complex called the Main Processing Facility (MPF). MENSA will replace the existing Gravel Gertie bunkers used for warhead assembly and disassembly on the eastern part of the campus, which are designed to collapse inward in the event of an explosion. Other new infrastructure for this project includes a support building and 16 lightning protector towers to accompany the MPF, as well as an associated plant building, gatehouses, vehicle inspection bays, substation buildings, security fences, access roads, and Sustainable Drainage System (SuDS) infrastructure.

Project MENSA’s completion has been delayed by more than seven years, and its expected cost is £1.36 billion over its original total budget of £0.8 billion. Construction progress at the site can be observed through satellite imagery and should be nearing completion of construction according to the MoD’s 2024 Major Project Portfolio data. 

Upgrades at AWE Aldermaston

AWE Aldermaston, where warhead design, development, manufacturing, assembly, and testing occur, is also undergoing significant upgrades and revitalization. In 2024, AWE announced two new infrastructure programs—the Future Infrastructure Programme (FIP) for general infrastructure and the Future Materials Campus (FMC) for nuclear material manufacturing and storage—to consolidate existing programs and invest in new ones to increase capacity for maintaining, manufacturing, and storing nuclear weapons. The procurement process for these multi-year, multi-billion pound projects began on April 22 and December 12, 2024, respectively. The FMC, in particular, will be a collection of facilities, including nuclear science and technology centers and laboratories, to be built at AWE Aldermaston. This program will replace two major projects that initially fell under the NWCSP—Project Pegasus and Project Aurora. 

Project Pegasus was described as a new enriched uranium storage and manufacturing facility at AWE Aldermaston that would replace the existing enriched uranium handling facility located at the A45 building. Work began in 2003, and the original projected service date was 2016. The approved cost was originally £634 million before it skyrocketed to £1.7 billion. After a six-year delay and a three-year pause, construction of the new storage facility began, and the manufacturing facility was scheduled to be finished by 2030. The severe delays were mainly due to challenges with the supply chain environment and an “overly complex technical solution” that resulted in additional construction and safety costs and a “reassessment” of the project design and requirements. 

The UK government was also in the early design phase of Project Aurora, an infrastructure project for a new plutonium manufacturing facility that would replace the current A90 building at AWE Aldermaston. This program was experiencing delays due to resourcing problems, supply chain shortages, and high-skilled workforce challenges. Project Aurora was removed from the NWCSP and added as an independent program to the MOD’s Major Projects Portfolio in 2022. Projects Aurora and Pegasus were both removed from the 2024 version of the MOD’s Major Projects Portfolio database, likely due to their absorption into the new FMC program.

The other central element of NWCSP is the delivery of a new hydrodynamics facility. In 2010, the United Kingdom and France signed the Teutates Treaty, which allowed for cooperation on warhead physics research between the two nations. From this agreement, the EPURE radiographic facility was built at Valduc in France, and a joint UK-France Technology Development Centre was established at Aldermaston. These facilities will support hydrodynamic research that will allow the study of the effects of aging and manufacturing processes on nuclear warheads without nuclear explosive testing. Because of the Teutates program, the UK’s original plans for a ‘Project Hydrus’ hydrodynamics facility were canceled. 

Outstanding Challenges 

The facilities described above are deemed crucial to the United Kingdom’s effort to modernize and refurbish its nuclear deterrent. However, the significant delays and cost overruns have elicited criticism from the public and concern from government authorities over the years. In August 2024, the House of Commons reported a spending deficit on nuclear programs across the Defence Equipment Plan. Over the next ten years (2023 to 2033), costs are forecasted at £117.8 billion, of which only £109.8 billion had been budgeted for when the report was released. 

Alongside these warhead development and infrastructure programs, the United Kingdom is also replacing its four SSBNs with the new Dreadnaught class, the first of which is expected to enter service in the early 2030s. This modernization has also been plagued by cost increases and threatens to be delayed, given maintenance issues with the existing fleet.

Moreover, the recent decrease in UK government transparency regarding the status of its nuclear arsenal and modernization program reflects a worrisome global trend. The United Kingdom has not publicly declared the approximate size of its stockpile since 2010, following the Obama Administration’s decision to release its stockpile number. In 2021, the MOD referred to the 2010 announcement again but did not explicitly say what the stockpile number was. Moreover, it said it would “no longer give public figures for our operational stockpile, deployed warhead or deployed missile numbers.”

Additionally, the MOD said in 2023 that it was withholding information on planned in-service dates for many of the above-referenced projects for “reasons of national security” and did not release this information in its 2022, 2023, and 2024 Major Projects Portfolio data. Finally, the MOD has published an annual update to Parliament since 2011 on the progress of nuclear weapons upgrades, but there has been no report published for 2023 or 2024.

While some of this backsliding is likely rooted in concerns about public perception of persistent programmatic delays, the overall picture raises concerns about a pattern of declining transparency and reduced public ability to monitor and hold the UK government accountable for its nuclear weapons program. 

In the spring of 2022, researchers at the Federation of American Scientists began reading newly released U.S. Defense Department budget documents to look for updates concerning the Pentagon’s priorities for the next fiscal year. As the researchers poured over hundreds of pages, two words suddenly captured their attention: the Biden administration’s Fiscal Year (FY) 2023 budget request had added “the UK” to a list of countries receiving upgrades to their “special weapons” storage sites under a 13-year NATO investment program. The term “special weapons” is often used by the U.S. government when referring to nuclear weapons. However, the United States has not deployed nuclear weapons in the United Kingdom for nearly two decades. Those two words sparked dozens of questions, years of continued research, and a new local movement of protests against the return of a potential nuclear mission to RAF Lakenheath.

This new report provides an account of the nuclear history of RAF Lakenheath and the role it played in the US nuclear mission until nuclear weapons were withdrawn in 2008. The report then explains the mounting evidence from three years of collection of documentation and observations that show the United States Air Force is re-establishing its nuclear mission on UK soil for the first time in nearly two decades.

As of February 2025, there are no known public indications that nuclear weapons have been deployed to RAF Lakenheath – we assess that the return of the nuclear mission is intended primarily as a backup rather than to deploy weapons now. However, if this were to happen, it would break with decades of policy and planning and reverse the southern focus of the European nuclear deployment that emerged after the end of the Cold War. Even without weapons present, the addition of a large nuclear air base in northern Europe is a significant new development that would have been inconceivable just a decade-and-a-half ago.

Read the full report here

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The authors would like to thank Matt Korda and Kate Kohn for their invaluable contributions to this report, as well as the Joseph Rowntree Charitable Trust for their support.

President Trump is moving quickly to push U.S. allies to invest even more in their own defense. NATO allies have already committed to spend 3% of their GDP on defense, yet the U.S. is now calling for them to spend at least 5%. It is likely that U.S. allies in East Asia will soon face similar calls to do more. Greater investments in conventional capabilities make a lot of sense. However, there are some U.S. policy experts, officials and academics calling for more U.S. allies to go nuclear to reduce U.S. defense requirements. These calls are dangerously misguided and ignore the threat any proliferation – including by U.S. allies – poses to American security interests. They must be rejected wholesale by the Trump Administration.  

One of the most enduring successes of U.S. national security policy has been its effort to limit the number of states with nuclear weapons. Predictions that dozens of countries might possess nuclear weapons did not materialize because of concerted U.S. actions. The risks include the reality that U.S. allies can and often do experience internal instability or even regime collapse, that any state with nuclear weapons creates a risk that those materials or knowhow can be stolen or diverted, that any state with nuclear weapon in a crisis might actually use those weapons, and lastly the reality that states with their nuclear weapons are less susceptible open to U.S. influence. There may be reasons why a state may want to go nuclear from their own perspective but there are few if any lasting benefits to American security that comes from proliferation to friends and allies.

Nine countries currently have nuclear weapons, but perhaps 40 additional states are technically advanced enough to build nuclear weapons if they chose to do so. Many of these states are U.S. allies or partners, including in Europe as well as Japan, South Korea, and even the island of Taiwan. That these states never went nuclear (although some tried) is due to a combination of factors, including the credibility of U.S. defense commitments to their security, the pressure America brought to bear when these states indicated a potential interest in building independent nuclear arsenals, and the recognition that if the world was serious about getting rid of all nuclear weapons then their spread was a step in the wrong direction.

The re-election of Donald Trump has understandably spooked many U.S. allies, renewing doubts that America will come to their aid. The growth of China’s military and economic power relative to the United States is adding to these concerns. More allies are asking now, just as they did during the Cold War if America would really risk Boston to protect Berlin, or Seattle to protect Seoul. As this question festers and as America’s relative power over China and other states ebbs, the lure to encourage U.S. friends to develop nuclear weapons of their own to deter or defeat an attack will grow. After all, the theory goes, why should the United States worry if its friends go nuclear?

In the real world, however, the spread of nuclear weapons anywhere complicates and undermines U.S. security. One reason is states are not always stable. In the 1970s, the U.S. supported its Treaty partner Iran acquiring nuclear reactors and advanced technology but in 1979, that regime was overthrown by the Islamic Revolution. Pakistan went nuclear when the U.S. needed its help fighting the Soviets in Afghanistan, and has faced wave after wave of instability and crisis. And South Korea is a more recent challenge. For the last few decades, South Korea was considered a stable and vibrant democracy – even hosting a Summit for Democracy last year. Under President Yoon, South Korea has voiced increasing interest in an independent nuclear arsenal. And just last year, a former Trump official, Elbridge Colby, expected to serve in a senior policy role at the Pentagon publicly encouraged South Korea to build their own nuclear weapons to deter North Korea and enable the U.S. to focus more on China. The situation in South Korea, with an impeached President and no clear sense of who controls the country’s military, would be a lot more dangerous if Seoul had nuclear weapons. 

This is not just an issue for newer nuclear weapons states. Prior to the Soviet Union’s collapse in 1991, a coup created confusion for days over exactly who had the ability to control Soviet nuclear weapons.  Following the USSR’s demise, nuclear weapons and materials remained at risk of theft and diversion for years and required massive U.S. efforts and investments to prevent their loss. And even the United States is not immune from these risks. The 2021 insurrection raised nuclear risk to the point that the Speaker of the House had to publicly ask the Chairman of the Joint Chiefs about the risk that President Trump might use nuclear weapons in a gambit to remain in power, and Chairman Milley took extraordinary steps to insert himself into the nuclear chain of command to preempt that risk. Any nuclear arsenal anywhere is a potential danger if political circumstances change.

And states with nuclear weapons create a nuclear risk if nuclear technology, materials and knowhow are stolen or diverted. Five of today’s nuclear weapon states – America, Russia, China, France, and Pakistan – have either knowingly or unwittingly helped other states go nuclear.  Even if theft or transfer were not an issue, when new states have gone nuclear in the past, others have followed. America’s nuclear success led the Soviet Union to build them as well. This in turn led the UK and France to follow suit. These four nuclear weapon programs fueled China’s desire to join the club. Beijing having the bomb drove India to do the same, which then led Pakistan to follow suit.  

And any nuclear state might decide one day to use those weapons. Every nuclear leader must get every nuclear decision right, every time or boom. The history of U.S. and Soviet nuclear deterrence is marked as much by nuclear misunderstandings and potential accidents as by stable deterrence. India and Pakistan have the same problem. It is reasonable to assume new nuclear states with nuclear weapons would encounter many of the same risks.

And finally, from a very direct Americentric point of view, each state that acquires their own nuclear weapons lessens the ability of the United States to influence, control or dictate security outcomes in that state and region. While not the message U.S. diplomats use openly when trying to work diplomatically to stop proliferation, the issue of influence is as relevant to U.S. allies as adversaries. To the extent that the U.S. security is enhanced by being able to heavily influence how states around the world act, then enabling the spread of nuclear weapons undermines that ability.

It is and will continue to be tempting for the next Administration to find rapid and easy solutions to long-standing security challenges. Empowering U.S. allies to do more so Washington can do and spend less, or focus more effectively on fewer challenges is an understandable policy outcome. But enabling, or looking the other way at the spread of nuclear weapons is not in America’s interests anymore today than it was in the 20th century.  

Today, the Bulletin of Atomic Scientists announced that the Doomsday Clock is 89 seconds to midnight. 

Created in 1974, the Clock is a symbolic representation of how close humanity is to global catastrophe—or midnight—due to man-made technologies. The Clock is set by the Bulletin’s Science and Security Board, a group of experts on nuclear risk, biological threats, disruptive technologies, and climate change. Each time the Doomsday Clock is set, it is a visual reminder of the work to be done.

While the Clock has remained at 90 seconds for the past three years, today, the Bulletin announced that the Clock has moved 1 second to midnight, symbolizing a time of “unprecedented danger.” This is the closest the Doomsday Clock has ever been to midnight, even through events like the Cuban Missile Crisis, the creation of the hydrogen bomb, 9/11, and North Korea’s first test of a nuclear weapon. The Science and Security Board explained that this change was due mainly to a rise in nuclear stockpiles, warming global temperatures, and advances in disruptive technologies. A “countdown to zero” metaphor, the Clock is used as a plea from scientists and experts for policy changes that would reduce the risk of nuclear war and mitigate the effects of climate change. 

Daniel Holz, the Chair of the Science and Security Board, stated that “the countries that possess nuclear weapons are increasing the size of all of their arsenals, investing hundreds of billions of dollars in weapons that can destroy civilization many times over.”

The Federation of American Scientists was founded over 75 years ago after the bombings of Hiroshima and Nagasaki with a commitment to the use of science and technology for the betterment of humanity. To this day, the staff continues to work towards the reduction of nuclear risks and to support evidence-based policy decisions.

In 2024, the Nuclear Information Project of the Federation of American Scientists reported on several of the risks that contributed to the clock’s hand moving forward. 

All nuclear weapons states are undergoing nuclear weapons modernization programs. While not all states are necessarily increasing the number of warheads in their stockpiles, a combination of nuclear signaling, the degradation of arms control, and massive spending indicate that we are entering an age of arms racing. All of these indicators demonstrate that states are further prioritizing nuclear weapons in their national security strategies, potentially at the expense of   more proximate security priorities. 

As long as nuclear weapons exist, nuclear war remains possible. The Nuclear Information Project provides transparency of global nuclear arsenals through open source analysis. It is through this data that policy makers can call for informed policy change. Pursuing policy options that lower the risks of nuclear war and global catastrophe should be of the utmost importance. In 2024, The Global Risk team at Federation of American Scientists proposed several options as part of FAS’s Day One Project.

Pursuing a Missile Pre-launch Notification with China as a Risk Reduction Measure

With tensions and aggressive rhetoric on the rise, the next administration needs to prioritize and reaffirm the necessity of regular communication with China on military and nuclear weapons issues to reduce the risk of misunderstandings. Details regarding a proposed agreement between China and the United States can be found in this policy memo. 

Removing Arbitrary Deployment Quotas for Nuclear Force Posture

Congress should ensure that no amendments dictating the size of the intercontinental ballistic missile force are included in future National Defense Authorization Acts. For more on reducing costs in the ICBM force and adjusting to current strategic objectives, read this policy memo.

Introducing Certification of Technical Necessity for Resumption of Nuclear Explosive Testing

The United States should continue its voluntary moratorium on explosive nuclear weapons tests and implement further checks on the president’s ability to call for a resumption of nuclear testing. On preventing environmental contamination, unnecessary spending, public health crises, and security threats due to resuming nuclear testing, read more here. 

Saving Billions on the US Nuclear Deterrent

Life-extending the existing Minuteman III missiles is the best way to field an ICBM force without sacrificing funding for other priorities. Read more in this policy memo.

Washington, D.C. – January 13, 2025 – Today, the Federation of American Scientists released “United States Nuclear Weapons, 2025”—its estimate and analysis of the U.S. nuclear weapons arsenal. The annual report, published in the Bulletin of the Atomic Scientists, estimates that the United States maintains a stockpile of approximately 3,700 warheads, about 1,700 of which are deployed. 

Under several successive presidential administrations, the United States has pursued an ambitious nuclear modernization program, including upgrades to each leg of its nuclear arsenal. Under the Biden administration, however, the debate has shifted to begin assessing ways that the United States could potentially increase the number of nuclear weapons that could be deployed on its current launchers by uploading more warheads. 

Despite mounting cost overruns and program delays in its nuclear modernization efforts, the incoming Trump administration has signaled it may pursue additional nuclear weapons programs and further expand the role that these weapons play in U.S. military strategy, based in part on the recommendations of the 2023 Strategic Posture Commission. 

Nuclear Signaling

In recent years, the United States sought to use its nuclear arsenal to signal both its resolve and capability to adversary nations—an effort likely to continue and grow in the coming years. Past efforts at nuclear signaling include increased nuclear-armed bomber exercises, updating nuclear strike plans, nuclear submarine visits to foreign ports, and participation in NATO’s annual Steadfast Noon nuclear exercise. In addition, the Biden administration announced that its new nuclear employment guidance determined “it may be necessary to adapt current U.S. force capability, posture, composition, or size,” and directed the Pentagon “to continuously evaluate whether adjustments should be made.” This language effectively leaves it to the incoming Trump administration to decide whether to expand the U.S. arsenal in response to China’s buildup (read a detailed FAS analysis by Adam Mount and Hans Kristensen here). 

Modernization and Nuclear Infrastructure

Nuclear modernization continues for all three legs of the nuclear triad. For the ground-based leg, the new ICBM reentry vehicle––the Mk21A––is expected to enter the Engineering and Manufacturing development phase in FY25. It will be integrated into the Sentinel ICBM and carry the new W87-1 warheads currently under development. The Sentinel ICBM program continues to run over-budget as all 450 launch centers must be renovated to accommodate the new missile, and new command and control facilities, launch centers, training sites, and curriculum for USAF personnel must be created. For the sea leg, the first Columbia-class ballistic missile submarine (SSBN)––the USS District of Columbia––passed its 50 percent construction completion metric in August 2024, and the USS Wisconsin passed 14 percent in September. The new SSBNs will include a reactor that, unlike the Ohio class SSBNs, will not require refueling for the entirety of its lifecycle. The program faces delays and is projected to cost five times more than the Navy’s estimates For the air leg, the Air Force is developing a new nuclear air-launched cruise missile (ALCM) known as the AGM-181 LRSO, as well as the B-21 Raider and new gravity bombs, including the B61-12 and B61-13. 

Throughout 2024, infrastructure upgrades at various U.S. ICBM bases were visible. This includes a new Weapons Generation Facility at Malmstrom Air Force Base and a Missile-Handling and Storage Facility and Transporter Storage Facility at F.E. Warren Air Force Base, as well as test silos at Vandenberg Space Force Base.

Finally, in addition to these ongoing upgrades, the United States is also considering developing a new non-strategic nuclear sea-launched cruise missile (SLCM-N), which was proposed during the first Trump administration. Despite the Biden administration’s attempt to cancel the program, Congress has forced the administration to establish the SLCM-N as a program of record. The SLCM-N was originally expected to use the W80–4 warhead that is being developed for the LRSO; however, this is currently being renegotiated. The warhead and delivery platform are expected to be finalized in early 2025.

The Nuclear Notebook is published in the Bulletin of Atomic Scientists and freely available here.

This latest issue follows the release of the 2024 UK Nuclear Notebook. The next issue will focus on China. Additional analysis of global nuclear forces can be found at FAS’s Nuclear Information Project.

ABOUT THE NUCLEAR NOTEBOOK 

The FAS Nuclear Notebook, co-authored by Hans M. Kristensen, Matt Korda, Eliana Johns, and Mackenzie Knight, is an effort by the Nuclear Information Project team published bi-monthly in the Bulletin of the Atomic Scientists. The joint publication began in 1987. FAS, formed in 1945 by the scientists who developed the nuclear weapon, has worked since to increase nuclear transparency, reduce nuclear risks, and advocate for responsible reductions of nuclear arsenals and the role of nuclear weapons in national security.

The Federation of American Scientists’ work on nuclear transparency would not be possible without generous support from the Carnegie Corporation of New York, Longview Philanthropy, the Jubitz Foundation, the New-Land Foundation, Ploughshares, the Prospect Hill Foundation, and individual donors.

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 at fas.org

The Department of Defense has finally released the 2024 version of the China Military Power Report. We will provide additional analysis of the Chinese arsenal in early 2025 but offer these observations for now:

The report estimates that China, as of mid-2024, had more than 600 nuclear warheads in its stockpile, an increase of roughly 100 warheads compared with the estimate for 2023 and about 400 warheads since 2019. As we have stated for several years, this increase is unprecedented for China and contradicts China’s obligations under the Nuclear Nonproliferation Treaty. DOD assesses that the Chinese nuclear buildup “almost certainly is due to the PRC’s broader and longer-term perceptions of progressively increased U.S.-PRC strategic competition.”

The breakdown of the DOD estimate comes with considerable uncertainty. It appears to assume that sufficient warheads have been produced to arm many – perhaps up to one third – of the silos in the three new ICBM silo fields in northern China. Different assumptions about how those silos will be armed greatly influence warhead projections:

Different assumptions about how China will arm it’s missile silos can significantly influence warhead number projections.

Matching the warhead estimate with the known force structure also depends on how many of the new liquid-fuel silos under construction in the mountains of central/southeastern China are operational, and how many of missiles carry multiple warheads. Other variables are how many warheads are assigned to the DF-26 IRBM launchers (probably not all of them), how many of the six SSBNs have been upgraded to the JL-3 SLBM and whether it is assigned multiple warheads, and how many DF-41 ICBM launchers are operational and how many warheads each missile is assigned.

As in previously years, the DOD report misleadingly describes the Chinese warheads as “operational.” This gives the false impression that they’re all deployed like Russia and U.S. nuclear warheads on their operational forces and has already created confusion in the public debate by causing some to compare all Chinese warheads with the portion of US warheads that are deployed. What DOD calls China’s “operational” warheads is equivalent to DOD’s entire nuclear warhead stockpile, whether deployed, operational, or reserve.

Except for perhaps a small number, the vast majority of Chinese warheads are thought to be in storage and not deployed on the launchers. This situation may be changing with a higher readiness level and emerging launch-on-warning capability.

The report repeats earlier projections that China might have over 1,000 warheads by 2030 but does not mention previous projections of 1,500 warheads by 2035. But this expansion requires additional plutonium production. The report confirms that China “has not produced large quantities of plutonium for its weapons program since the early 1990s” and anticipates that it “probably will need to begin producing new plutonium this decade to meet the needs of its expanding nuclear stockpile.”

ICBMs

The report lists 550 ICBM (Intercontinental-Range Ballistic Missile) launchers with 400 ICBMs, an increase of 50 launcher and 50 missiles compared with last year’s report. That is more ICBM launchers than the United States has, although far from all the Chinese silos are armed.

It is unclear what operational status a missile must have to be included in the count or whether 400 is simply the total number of missile available for the launchers. If it means operational (which I don’t think is the case), then 400 ICBMs would imply a significant number of the new silos loaded.

The report includes a map that appears to match previous FAS analysis of the three silo fields:

The DOD map of the three northern silo fields appears to match earlier FAS analysis.

The report states that the three ICBM fields were probably completed in 2022 and that PLARF has loaded “at least some” ICBMs into the silos. The report says China “probably continues to arm” the silo fields.

For now, the new silo fields appear intended for the solid-fuel DF-31A. The DOD report identifies a new version of the DF-31 (CSS-10 Mod 3), which is probably the version intended for the silos.

The ICBM estimate appears to come with several caveats. One is that the number of ICBM launchers is not the same as the number of operational ICBMs. A silo launcher appears to be counted when construction is completed, whether it is operational with missile or not. To get to 550 launchers, it is necessary to count everything, including all the 320 silos in the three new northern silo fields as well as all the silos under construction in the southeastern mountains.

The report says the silo construction in the central/southeastern part of China will probably result in about 50 silos there, matching estimates made by FAS and others. The report confirms that those new silos are intended for DF-5 liquid-fuel missiles and appears to suggest that at least two brigades with the new silos are intended for the new multi-megaton DF-5C that it says China is now fielding.

The 2024 China Military Power Report confirms reports by FAS, Ben Reuter, and Decker Eveleth about the modernization of the DF-5 silos in central/southeastern China.

The report does not say how many of the new DF-5 silos – if any – have been loaded with missiles.

The new DF-41 ICBM is not said to be deployed in silos but so far only as a road-mobile system in a few brigades. But the DOD report says China might pursue silo and rail deployments for the missile in the future.

The new DF-27 is described as dual-capable and while capable of shorter ICBM ranges mainly be intended for conventional IRBM missions.

IRBMs and MRBMs

The report lists 250 IRBM (Intermediate-Range Ballistic Missile) launchers with 500 missiles, the same as in 2023. This force apparently consists entirely of the DF-26, of which the report identifies three versions. Previously an anti-ship version was identified in addition to the basic version, so it is unclear if the first two versions are used to differentiate between the conventional and nuclear versions. Regardless, the DF-26 is replacing the DF-21 MRBM (Medium-Range Ballistic Missile) and the report says there are no longer any brigades with “dual nuclear-conventional capable DF-21Cs” (which is odd because the C was the conventional and the A was the nuclear).

The DF-17 MRBM maneuverable glide vehicle is described as conventional.

SSBNs

The report says that China continues to operate six Jin-class Type 094 SSBNs (nuclear powered ballistic missiles submarines) equipped with either the JL-2 or the 10,000-km range JL-3 SLBM (Sea-Launched Ballistic Missile). Despite the longer range of the JL-3 SLBM, it is not capable of targeting the Continental United States from the South China Sea. A submarine would have to deploy up into the shallow Bohai Sea to be able to target part of CONUS.

The DOD report says the six SSBNs “are conducting at sea deterrent patrols.” In the U.S. Navy, that means the missiles are armed with nuclear warheads, but the DOD report does not explicitly say this is the case for China.

The report says the SSBNs are “representing the PRC’s first viable sea-based nuclear deterrent,” and says China “has the capacity to maintain a constant at sea deterrent presence.” More Jin-class SSBNs apparently are under construction.

The next-generation Type 096 apparently is not yet under construction. It is said it will get a new longer-range missile, although it is unclear if that is older language that used to refer to the JL-3. The report says the Type 096 SSBN “probably is intended to field MIRVed SLBMs,” indicating that the SLBMs on the current Jin-class are not.

Bombers

The report repeats previous statements that China is fielding a nuclear version of the H-6 medium-range bomber. The nuclear version H-6N is capable of carrying a large air-launched ballistic missile that “may be” nuclear capable. Although China is often said to have a Triad, the air-leg is nascent and still only includes one brigade that is developing tactics and procedures for the PLAAF nuclear mission. 

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As mentioned above, we will provide additional analysis of the DOD report and Chinese nuclear forces early in the new year. More information: The Nuclear Information Project

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The Federation of American Scientists’ work on nuclear transparency would not be possible without generous support from the Carnegie Corporation of New York, Longview Philanthropy, the Jubitz Foundation, the New-Land Foundation, Ploughshares, the Prospect Hill Foundation, and individual donors.