Deterrence defined

Ask three people to define “deterrence” and you’ll probably get seven or eight different definitions and at least one uncertain shrug.

Deterrence is a complex topic, particularly when discussed in the context of the United States’ defense policy. Add in the threat of nuclear weapons, and the complexity builds. 

At its heart, deterrence simply means preventing something. Most people associate deterrence with preventing war, keeping America safe, and convincing potential adversaries to seek alternatives to aggression. Under those umbrellas, you will find many theories, approaches, strategies, and schools of thought.

Yes, it’s complicated, but National Security Science has sorted through the jargon to compile a simple deterrence dictionary (okay, it’s really a glossary, but we liked the alliteration). So, before you dive into deterrence, take a look at the definitions at the end of this article.

How does Los Alamos contribute to deterrence? 

For nearly 80 years, the United States has relied on nuclear deterrence—the threat of using nuclear weapons to discourage other nations from military aggression—to ensure global stability and prevent war.

For nuclear deterrence to work, the nuclear deterrent has to be credible. That's where Los Alamos National Laboratory comes in.

Los Alamos, which is overseen by the Department of Energy’s National Nuclear Security Administration (NNSA), is responsible for the design, production, and certification of current and future nuclear weapons. Los Alamos designed five of the seven weapons systems currently in the U.S. nuclear stockpile. Today, Los Alamos is responsible for maintaining four of those systems: the B61 family of gravity bombs, the W76 family of warheads, the W78 warhead, and the W88 warhead. (Lawrence Livermore National Laboratory is responsible for the other three systems: the B83 bomb and the W80 and W87 warheads.)

“The Stockpile Stewardship Program provides the scientific and engineering capabilities that the Laboratory depends on to steward a safe, secure, and reliable stockpile,” says Charlie Nakhleh, associate director for Weapons Physics at Los Alamos. “These cutting-edge research tools, facilities, and programs also underwrite our ability to execute the demanding stockpile modernization program that is currently underway, and, looking further ahead, they provide the foundation for the Laboratory’s ability to respond quickly and innovatively to future threats and developments.”

Through stockpile stewardship, Los Alamos works with other labs, plants, and sites in the nuclear enterprise to assess and ensure the safety, security, and effectiveness of the B61, W76, W78, and W88. Each of these weapons requires surveillance (a thorough physical examination of a representative sample weapon that starts at the Pantex Plant and continues at other sites) and routine maintenance. If at any time Los Alamos becomes concerned about the health of a weapon, the weapon may be retired, or in some cases, refurbished through a life extension, alteration, or modification, each of which provides various degrees of updates that enable the United States to maintain a credible nuclear deterrent without producing new weapons or conducting underground nuclear tests.

For weapons at the end of their original design life, Los Alamos may increase the weapon’s lifespan through a life extension program (LEP), which addresses aging and performance issues, enhances safety features, and improves security in an increasingly complicated and uncertain global environment. Through an LEP, scientists and engineers analyze a weapon’s components and, based on that analysis, reuse, refurbish, or replace certain components. An LEP helps the United States maintain a credible nuclear deterrent without producing new weapons or conducting underground nuclear tests.

Los Alamos may also conduct alterations (alts), which are changes to a weapon’s systems, subsystems, or components. Not as extensive as an LEP, an alteration is a limited-scope change that affects the assembly, maintenance, and/or storage of a weapon.  The alteration may address identified defects and component obsolescence without changing a weapon’s operational capabilities.

Weapons may also undergo modifications (mods), which change a weapon’s operational capabilities. A modification may enhance the margin against failure, increase safety, improve security, replace limited-life components, or address identified defects and component obsolescence.

The U.S. nuclear stockpile

B61

Numerous modifications have been made to the B61 gravity bomb since it first entered service in 1968. The aging weapon system recently underwent a life extension that consolidated three B61 weapon designs (the B61-3, -4, and -7) into one updated design: the B61-12. The B61-12 LEP refurbished, reused, or replaced all the bomb’s nuclear and nonnuclear components. The overhaul resulted in a more accurate weapon that’s expected to remain in service another 20 years. If it is ever used, the B61-12 will be air-delivered by the B-2 stealth bomber or a fighter aircraft.

Looking forward: The 2024 National Defense Authorization Act authorized a new variant of the B61: the B61-13. “This weapon will replace some of the B61-7 weapons in the stockpile and have the safety, security, and accuracy of the B61-12 with an ability to hold large area or hard targets at risk,” explained NNSA Administrator Jill Hruby at the 2024 Nuclear Deterrence Summit. “We will decrease the number of B61-12s by the number of B61-13s we build, so the number of weapons in the stockpile will not increase because of this decision.”

W76

Used atop Trident II submarine-launched ballistic missiles on Ohio-class submarines, the W76 warhead was introduced into the stockpile for the Navy in 1978. Since then, the warhead has undergone a life extension program, resulting in the W76-1, and a modification, resulting in the low-yield W76-2.

Los Alamos and Sandia national laboratories are the design agencies for the W76-1 LEP, which wrapped up in 2018 and extended the warhead’s service life from 20 to 60 years.

The W76-2 is a modification of the W76-1 that provides a low-yield, sea-launched ballistic missile warhead capability. The first W76-2 was produced in February 2019, at the Pantex Plant in Amarillo, Texas.

W78

The W78 was first deployed in 1979 on U.S. Air Force Minuteman III intercontinental ballistic missiles. The warhead is the one Los Alamos–designed weapon system that has not undergone a life extension, alteration, or modification.

W88

The W88 warhead, which can be launched on missiles from Ohio-class submarines, entered the stockpile in 1988. In 2012, the W88 underwent an alteration—called the W88 Alt 370—to replace the warhead’s arming, fuzing, and firing subsystem and to include safety enhancements. In 2015, the Nuclear Weapons Council expanded the scope of the alteration and asked Los Alamos to replace the W88’s conventional high explosives and related components. Since October 2021, updated W88s have been gradually replacing older W88 warheads in the stockpile.

Looking forward: The W93 warhead will be deployed on both Ohio- and Columbia-class submarines beginning in the 2030s. As the warhead’s lead physics design agency—the organization responsible for the design and certification of the nuclear warhead package and some of the nonnuclear components—Los Alamos must determine how the W93 design will meet the requirements proposed by the Department of Defense. The design will be based on currently deployed and previously tested weapons and will incorporate modern technologies that improve safety, security, and flexibility to address future threats. 

Annual assessment

Los Alamos continually assesses the health of the B61, W76, W78, and W88. Each September, these assessments culminate in a letter from the Lab director to the secretary of energy, the secretary of defense, and the chair of the Nuclear Weapons Council. This letter informs the president of the United States of the director’s confidence that the B61, W76, W78, and W88 are safe, secure, and effective.  

“This past year alone, NNSA has delivered more than 200 modernized weapons to the Department of Defense. There should be no doubt in anyone’s minds: NNSA is modernizing our stockpile both on-schedule and at pace.” —NNSA Administrator Jill Hruby at the 2024 Nuclear Deterrence Summit

Stockpile stewardship tools and capabilities (just a few of many)

The Laboratory’s capabilities range from advanced supercomputers that support the calculation, modeling, simulation, and visualization of complex nuclear weapons data to facilities where massive amounts of high explosives expose weapons to extreme environments so scientists can monitor how the weapons systems react.

DARHT

The Dual-Axis Radiographic Hydrodynamic Test (DARHT) facility uses two massive electron accelerators to produce high-speed images of mock nuclear devices as they implode at speeds greater than 10,000 miles an hour. “DARHT has become the principal U.S. nonnuclear testing facility where nuclear weapons can be studied in full-scale with surrogate materials,” says research and development engineer George Laity. “These experiments provide a unique opportunity to validate the physics and engineering models used to assess and certify the stockpile, evaluate designs as we modernize our weapon systems, and provide experimental testing capabilities that support global security missions. All these capabilities are exercised to increase our confidence in the overall nuclear deterrent.”

Scorpius

Los Alamos leads the Advanced Sources and Detectors Project, also known as Scorpius, a new diagnostic tool that will be housed underground at the Nevada National Security Site. Scorpius, a linear accelerator that is scheduled to be completed by 2030, will capture x-ray images of subcritical experiments, which use small amounts of plutonium.

“We are building something that is going to get used for decades,” says Mike Furlanetto, senior director of the project. “Knowing the impact of getting this data about plutonium and the impact these findings will have on our work at Los Alamos is thrilling. Scorpius will increase our ability to make devices safer and more secure and will prepare us to meet new military needs.”

Supercomputers

For decades, high-performance computing has facilitated the success of stockpile stewardship. Supercomputers enable large-scale data analysis and visualization capabilities that help scientists test their hypotheses and solutions and make informed decisions about the nation’s deterrent.

In 2023, the Lab began the deployment of two new supercomputers, Crossroads and Venado, which will advance Los Alamos’ ability to study complex physical systems for science and national security.

Pit production

A plutonium pit is the core of a nuclear weapon—a pit compressed by explosives generates nuclear energy, or yield. Los Alamos is currently developing the processes for manufacturing pits for the W87-1 warhead. 

Detonator production

For a plutonium pit to implode inside a nuclear weapon, the pit must be compressed uniformly by the high explosives that surround it. The high explosives are triggered by small devices called detonators. Since 1989, detonators for all nuclear weapons in the U.S. stockpile have been manufactured by Los Alamos.

Where science and strategy meet

“At Los Alamos, deterrence is our business,” says Kirk Otterson, a program manager in the Lab’s National Security and International Studies Office (NSIS). 

But deterrence theory, planning, strategy, and policy are unlike science, engineering, and technology—the fields that dominate most work at the Lab. Los Alamos leaders say bridging that gap between science and policy can be tricky but is necessary. Defense strategy must drive technical decisions such as how the Lab should allocate resources and what capabilities the U.S. military needs. Likewise, technical information can inform policy.

“We provide advice to decision-makers based on sound scientific and technological knowledge and understanding,” explains Los Alamos Director Thom Mason.

Otterson explains that the Lab’s NSIS office provides decision support on national security and technology issues relevant to the Los Alamos mission. “NSIS exists to help advise policymakers on what is technically possible and to advise technologists on what is policy desirable. We help bridge the gap between policymakers, senior Lab leadership, and technical communities, and serve as a think tank and action group,” he says. “What do we need to defend the country? What does that cost? How long will it take to produce it? These are technical questions tied to strategic planning.” 

In 2019, John Scott, the Lab’s Weapons Physics Theoretical division leader, kicked off an effort focused on the intersection of policy and technology by initiating a series of workshops called the Director’s Strategic Resilience Initiative, or DSRI. 

“DSRI was started as a means to spur cross-disciplinary technical work that looked at how we might maintain the efficacy of our stockpile given the quickly changing global and political landscape and our adversaries’ evolving capabilities,” Scott says. “Our aim is to demonstrate that Los Alamos, with its strong technical reputation in all things nuclear, can be a convening authority for policy decisions and establish a dialogue between policy and technical communities.”

Scott says that policymakers and technical experts must work together. “Policymakers typically do not have technical training as part of their background and will rely heavily on technical expertise on new and emerging technologies. This demands that as technical folks, we need to be able to communicate challenging technical information to nontechnical folks. We need to do a good job of elaborating on the art of the possible and the practical.” 

Andrew Ross, who holds a joint appointment at Los Alamos and Texas A&M University, started at the Lab in 2021 to help coordinate the DSRI workshops. Ross and his colleagues engage with policymakers, think tank representatives, academics, and technical subject matter experts to bridge the gap between policy and technical experts and inform, frame, and shape the debate on deterrence.

“I have spent my entire career at the intersection of policy and technology,” Ross says. Topics the DSRI workshops examine include the role of nuclear weapons in U.S. strategy, strategic stability, escalation management, and the future of arms control.

“We bring together people with a diverse range of perspectives as we examine national security and defense planning in a rapidly changing geopolitical environment,” Ross says. “We don’t always agree; there’s never going to be a self-evident right answer, and the game is never over.”

But Ross says he is optimistic about the contributions the workshops are making to deterrence planning and policy. “Some options are better than others, and we need to identify those options and figure out how the Lab can facilitate those options. It’s the whole reason we’re here.” ★

“Science-based stockpile stewardship put the laboratories in a powerful policy position because the responsibility of determining the health of the stockpile was theirs. If they ever believed that we had to go back to testing, they would have to say so.
This is where scientific integrity comes in: You have to be able to say, no matter what the policy is, ‘This is what the science tells us.’”
—Former Assistant Secretary for Defense Programs in the Department of Energy, Victor Reis, who spearheaded the development of the Stockpile Stewardship Program

Deterrence dictionary

Deterrence: Discourages or prevents an adversary from taking unwanted actions, such as an armed attack. 

Compellence: Encourages an actor to take a certain action. Compellence is closely related to but different from deterrence.

Deterrence by denial: Deters an action by making the action infeasible or unlikely to succeed, thus denying a potential aggressor confidence in attaining its objectives.

Deterrence by punishment: Threatens severe penalties if an attack occurs. Also called deterrence by cost imposition.

Deterrence by resilience: Relies on the ability to withstand, fight through, and recover quickly from disruption.

Nuclear deterrence: Relies on a country’s possession of nuclear weapons systems and a plan for the employment of such nuclear weapons.

Integrated deterrence: Leverages all instruments of national power (such as diplomatic, information, military, economic).

Strategic deterrence: Integrates all capabilities in all domains (land, sea, air, space, cyber, and information) across all the combatant commands, government organizations, and alongside allies.

Direct deterrence: Prevents attacks on a country’s  territory.

Extended deterrence: Discourages attacks on third parties, such as allies or partners.

General deterrence: Prevents unwanted actions over the long term and in noncrisis situations. 

Immediate deterrence: Prevents a specific, imminent attack, most typically during a crisis.

Tailored deterrence: Applies classic deterrence notions to specific cases. 

In-domain deterrence: Deters attacks in which the intended consequences unfold in the same domain as the target. U.S. military operations can be divided into domains such as land, sea, air, space, and cyberspace or information.

Cross-domain deterrence: Deters attacks in which the intended consequences unfold in a different domain than the target. 

Cyber deterrence: Uses cyberspace operations to deter both malicious adversary cyberspace activities and kinetic conflict.

Escalation management: Keeps military confrontations from erupting into war and keeps limited wars from spinning out of control.

Deliberate escalation: Deliberately increases the intensity or scope of an attack.

Space deterrence: Deters attacks on space assets (primarily satellites and space flight), attacks in space, and attacks from space.