https://crsreports.congress.gov
Updated July 19, 2024
Defense Primer: Strategic Nuclear Forces
The United States is in the process of modernizing its
strategic nuclear forces. This modernization effort includes
numerous Department of Defense (DOD) major defense
acquisition programs, some of which are annually assessed
by the Government Accountability Office, and warhead
modernization programs implemented by the National
Nuclear Security Administration (NNSA), a semi-
autonomous agency in the Department of Energy. In 2023,
the Congressional Budget Office estimated that U.S.
programs to operate and modernize nuclear forces would
cost $756 billion over the next 10 years. The FY2025 DOD
budget requests “$49.2 billion for the modernization,
sustainment, and operations of all three legs of the nuclear
triad.” Members of Congress have shown strong interest in
conducting oversight of U.S. nuclear modernization efforts.
The Nuclear Triad
Since the early 1960s, the United States has maintained a
“triad” of strategic nuclear delivery vehicles. These include
long-range land-based intercontinental ballistic missiles
(ICBMs), long-range submarine-launched ballistic missiles
(SLBMs) on strategic nuclear submarines (SSBNs), and
long-range heavy bombers. The U.S. nuclear warhead
stockpile has decreased in number as the United States
changed nuclear planning requirements after the Cold War
and complied with arms control agreements.
U.S. strategic forces are currently limited by the 2011 U.S.-
Russian New START treaty. Table 1 displays U.S. nuclear
forces, as of September 1, 2022, accountable under that
treaty. The United States had 1,419 warheads deployed on
662 missiles and bombers as of March 1, 2023, according to
a more recent State Department fact sheet. The State
Department has stated that the United States “is prepared to
adhere” to the treaty’s central limits (1,550 deployed
warheads on 700 deployed strategic launchers; 800 total
strategic launchers) “as long as it assesses the Russian
Federation is doing so.”
Table 1. U.S. Strategic Nuclear Forces in 2022
Source: U.S. Department of State. New START Treaty Aggregate
Numbers of Strategic Offensive Arms, September 1, 2022.
a. The treaty attributes one warhead to each deployed bomber,
although each could carry up to 20 bombs or cruise missiles.
Rationale for the Triad
Early in the Cold War, the United States developed three
types of nuclear delivery vehicles, in large part because
each of the military services wanted part of the U.S. nuclear
arsenal. Eventually, DOD came to argue that different
basing modes’ complementary strengths could enhance
nuclear deterrence. As the 2010 Nuclear Posture Review
(NPR), a periodic assessment of U.S. nuclear policy,
summarized the post-Cold War evolution of this thinking:
[SSBNs] and the SLBMs they carry represent the
most survivable leg of the U.S. nuclear Triad.…
Single-warhead ICBMs contribute to stability, and
like SLBMs are not vulnerable to air defenses.
Unlike ICBMs and SLBMs, bombers can be visibly
deployed forward, as a signal in crisis to strengthen
deterrence of potential adversaries and assurance of
allies and partners.
The U.S. government has reaffirmed the value of the
nuclear triad and the importance of its modernization in a
series of NPRs. The Obama Administration stated in the
2010 NPR that the unique characteristics of each leg of the
triad were important to “maintain strategic stability at
reasonable cost, while hedging against potential technical
problems or vulnerabilities.” The Trump Administration
stated in the 2018 NPR that “the triad’s synergy and
overlapping attributes help ensure the enduring
survivability of our deterrence capabilities against attack
and our capacity to hold a range of adversary targets at risk
throughout a crisis or conflict.” The Biden Administration’s
2022 NPR argued that “maintaining a modern triad
possessing these attributes—effectiveness, responsiveness,
survivability, flexibility, and visibility—ensures that the
United States can withstand and respond to any strategic
attack, tailor its deterrence strategies as needed, and assure
Allies in support of our extended deterrence commitments.”
Current Forces and Modernization Plans
ICBMs
Before implementing the New START Treaty, the United
States deployed 450 Minuteman III ICBMs at Air Force
bases in Wyoming, Montana, and North Dakota. Under
New START, the number has declined to 400 deployed
missiles, although the Air Force has retained all 450 silo
launchers. While each Minuteman III missile originally
carried three warheads, the United States deploys the
missile with a single warhead in order to comply with New
START levels. The Air Force has completed life extension
programs (LEPs) to improve the accuracy and reliability of
the Minuteman.
The Air Force is also developing a new ICBM, the Sentinel,
previously known as the Ground-based Strategic Deterrent
