Federation of American Scientists Releases Latest United States Edition of Nuclear Notebook
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
FAS estimates that the United States maintains a stockpile of approximately 3,700 warheads, about 1,700 of which are deployed.
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