NATO Nuclear Deterrence Security & Defense
Issue Brief October 7, 2024

Strategic stability in the third nuclear age

By Matthew Kroenig

Executive summary

This is an issue brief about global strategic stability in the 2020s and 2030s. It draws heavily on the 2023 final report of the Congressional Commission on the Strategic Posture of the United States. It will argue that the world is entering a third major period in its nuclear history that will resemble the Cold War much more than the post-Cold War period of 1989 to 2022.1The author is grateful to Brad Roberts for this conceptualization of the major periods of global nuclear history. Strategic stability in this new period will depend less on dialogue, arms control, and risk reduction measures and rather more on ensuring that the United States and NATO maintain an effective strategic deterrent to deal with the growing threats posed by revisionist, autocratic, nuclear-armed states. This will require strengthening US and NATO strategic posture, including: conventional force posture; US strategic nuclear forces; nonstrategic nuclear forces; and integrated air and missile defenses. It is likely that there will be an absence of binding arms control agreements among the major powers for the foreseeable future, and the United States and its allies should focus instead on other risk reduction measures. Perhaps the most important contribution most NATO allies can make to strategic stability is to prepare their governments and publics for this third nuclear age.

Defining strategic stability

Strategic stability is a situation in which nuclear-armed states lack the incentive to conduct a nuclear first strike. Strategic stability is strengthened by secure, second-strike capabilities that give states the confidence that they can deter their adversaries by threatening to absorb an enemy nuclear first strike and retaliate with a devastating second strike. So long as both states understand that they cannot benefit from striking first, then nuclear deterrence should hold.

Strategic stability can also be strengthened by arms control agreements. Arms control can place strict numeric limits on the size of states’ nuclear arsenals, preventing nuclear arms races. They can also seek to limit particularly destabilizing types of nuclear weapons systems—those that might give rise to nuclear first-strike incentives. Finally, arms control can include transparency measures, such as inspections regimes and missile launch notifications, that can reduce mistrust and build confidence.

Geopolitics also influences strategic stability. What are the geopolitical goals and nuclear strategies of the major nuclear powers? Are they revisionist or status quo in their geopolitical orientation? Do they place nuclear weapons at the center of their defense and military strategies and doctrine, or do they seek to reduce reliance on nuclear weapons? Revisionist powers that emphasize nuclear threats in their strategies pose a particular challenge to strategic stability.

Given the recent return of great power rivalry in the international system, and multiple revisionist powers that are relying more on nuclear weapons, geopolitical considerations may be the most salient factor affecting strategic stability today and in the foreseeable future.

The three nuclear ages

The world is entering a third nuclear age. The first nuclear age was the Cold War. Nuclear weapons were central to geopolitical and military competitions. The United States and the Soviet Union engaged in several high-stakes nuclear crises. President John F. Kennedy himself estimated that the Cuban Missile Crisis carried a fifty-fifty chance of nuclear war. Washington and Moscow also participated in an intense nuclear arms competition. The arms race was stabilized only after a decades-long arms competition that left both sides with tens of thousands of nuclear weapons. The Cold War ended in part due to the Reagan administration’s defense buildup of the 1980s and Moscow’s fear that it would not be able to keep pace in a renewed arms competition. Strategic stability was maintained in the Cold War mostly by ensuring that the United States had a robust nuclear posture capable of deterring Soviet aggression.

The second nuclear age was the post-Cold War period. In this period, great power competition receded to the background of international politics. There was hope that the major powers could cooperate on shared challenges, and the greatest threats were posed by rogue states, terrorists, and other transnational threats. Nuclear weapons were not seen as central to these challenges and reducing reliance on nuclear weapons became a stated goal of US nuclear policy. In this environment, arms control and arms reductions were fairly easy. Washington and Moscow signed a series of formal arms control agreements and reduced the size of their arsenals from tens of thousands of nuclear weapons to 1,550 strategic deployed warheads each. Under President Barack Obama, the United States even emphasized a vision for the complete elimination of nuclear weapons. In this period, strategic stability was maintained by ensuring the United States and NATO had a safe, secure, and effective nuclear force, but also by strong assurances to Moscow—through arms control, strategic stability dialogues, and other measures—that the West was not seeking to undermine the Russian Federation’s deterrent.

The second nuclear age is over, and lessons we learned about strategic stability from 1989 to 2021 are less relevant to the period we are now entering. The third nuclear age will likely resemble more closely the Cold War, although in many ways it will be more challenging.

The third nuclear age

This section describes the coming third nuclear age, including the threat environment, US and NATO nuclear strategy, and recommendations for US and NATO strategic posture and strategic stability.

Security environment

The nuclear security environment facing the United States and NATO is in many ways more challenging than during the Cold War.

Russia is pursuing a revisionist foreign policy that includes the use of force against neighboring states in an effort to reconstitute a Russian sphere of influence in its near abroad. In recent years, Russian President Vladimir Putin has invaded or used military force in several neighboring states including Ukraine, Georgia, Belarus, Moldova, Kazakhstan, and Azerbaijan.

Russia has placed nuclear weapons at the center of its defense strategy. Its “escalate-to-de-escalate” strategy envisions using limited nuclear first strikes in a major war with NATO in a bid to force Western leaders to back down and sue for peace on terms favorable to Moscow. This doctrine includes a possibility for nuclear first use even in a war that Russia initiates. In the war in Ukraine, we have seen Putin issue a number of explicit nuclear threats. When Ukraine succeeded in a successful counteroffensive in the late summer of 2022, many analysts believed there was a significant risk of Russian nuclear use.

Russia is building a new nuclear force to back up its nuclear strategy. Moscow has just completed modernizing all three legs of its nuclear triad. It also is adding to its stockpile of more than two-thousand nonstrategic nuclear weapons. These nonstrategic nuclear weapons are intended for battlefield use and include low-yield weapons on a wide-range of delivery vehicles, such as: mines, torpedoes, depth charges, artillery, short-range missiles, air and missile defense interceptors, and more. Russia is also building a new generation of “exotic” nuclear weapons, including nuclear-armed submarine drones, nuclear-armed and -powered cruise missiles, and nuclear-armed hypersonic missiles.

Russia has also undermined the post-Cold War arms control architecture with the West, cheating on or withdrawing from nearly every major arms control treaty. The New START Treaty remains in place but is on life support. Russia has announced that it is suspending compliance with the treaty, though there is no indication that its nuclear weapons have expanded beyond the treaty’s numerical limits. When New START expires in January 2026, it is likely that there will be no major arms control agreements among the major powers for the first time since the early 1970s.

China represents the biggest change to the US and NATO nuclear threat environment—and poses the greatest state-based threat to global order. The threat crosses multiple domains including economic, technological, diplomatic, governance and human rights, and military. The People’s Republic of China has border and maritime disputes with nearly all of its neighbors, and it has vowed to take Taiwan by military force if necessary.

China is engaging in the most rapid strategic forces buildup the world has seen since the 1960s. For decades China maintained a “lean and effective” arsenal of 200 or so nuclear weapons, but Beijing is on pace to field 1,000 nuclear weapons by 2030 and 1,500 by 2035, making the nation a nuclear peer with the United States and Russia. This means that for the first time in history, the United States and NATO will need to face two near-peer nuclear powers, China and Russia, at the same time.

China has traditionally maintained a nuclear “no first use” policy, but the US Department of Defense publicly dismisses this policy as window dressing. China may very well use nuclear weapons first in a high-stakes conflict regardless of its stated policy. Moreover, China has learned from the war in Ukraine that threats of nuclear escalation are effective in deterring Western leaders from intervening in a conflict with a nuclear power.

The motivations behind China’s nuclear buildup are unclear. There are three possibilities that are not mutually exclusive. First, the buildup may be largely political and symbolic in nature. Chinese President Xi Jinping has said that he wants to build a “first-class military” by 2035, and having a first-class strategic force would fit with that goal. It is possible, therefore, that he has demanded a nuclear force on par with the other major powers, and China is building such a force even though the Chinese People’s Liberation Army (PLA) is not quite sure what they will do with it.

Second, it is possible that this is part of China’s strategy for invading Taiwan. Xi has asked the PLA to give him the ability to invade Taiwan by 2027. By enhancing its ability to hold the US homeland at risk with the threat of nuclear war, China may hope to deter US intervention in a Taiwan Strait contingency. Finally, the buildup may be part of a change of China’s nuclear strategy. China may be moving to a “counterforce” nuclear targeting strategy that would give it the ability to blunt American or Russian nuclear forces with a large-scale nuclear first strike.

A fourth floated possibility, that the buildup is merely an attempt to maintain a secure, second-strike capability as the United States modernizes its nuclear forces and missile defenses, is implausible for a variety of reasons. If China were interested in building a more survivable, second-strike capability, it would not, for example, invest in a large number of silo-based warheads, which present easy targets to an adversary.

North Korea, Iran, and nuclear terrorism remain concerns. In addition to the two major nuclear powers, the United States and NATO must also contend with rogue states. North Korea now has dozens of nuclear warheads and intercontinental ballistic missiles (ICBMs) capable of reaching the US homeland. It also is working to build a more sophisticated force to include submarine-launched missiles, solid-fuel missiles, and nonstrategic nuclear weapons.

Iran maintains an advanced nuclear fuel-making capability and the US Department of Defense estimates that Iran’s “breakout time” to one-bombs-worth of weapons grade material is about twelve days. This means that Iran could be a nuclear-armed power in the near future.

Finally, while less of a threat in relative and absolute terms than two decades ago, there remains the possibility that terrorist groups or nonstate actors could engage in acts of nuclear terrorism.

Other nuclear powers must factor into discussions of global strategic stability. The nuclear capabilities of the United Kingdom and France also contribute to NATO nuclear deterrence. During the Cold War, strategic planners concluded that strategic deterrence ultimately rested on the strategic balance between the major nuclear powers, and that conclusion continues to hold today. Israel is widely believed to possess nuclear weapons, but maintains a policy of “strategic ambiguity” and neither confirms nor denies the existence of its nuclear capabilities. If Iran were to build nuclear weapons, however, Israel would be tempted to become a declared nuclear power. India and Pakistan have been engaged in a long-standing rivalry and both possess growing nuclear capabilities. Many in this field believe a South Asia conflict may present the world’s greatest risk of nuclear escalation. The United States and NATO would like to limit the arms race and prevent nuclear conflict in South Asia. Israel, India, and Pakistan do not figure prominently in US and NATO nuclear planning because they are neither targets of US and NATO nuclear deterrence, nor formal treaty allies that fall under the US or NATO nuclear umbrella.

Emerging twenty-first century technologies also figure into strategic stability. Decades ago, the term strategic forces was synonymous with nuclear weapons; now it refers to weapons with potential strategic effect such as missile defenses, advanced conventional strike including hypersonic missiles, cyber and space capabilities, artificial intelligence, and more. Some scholars have worried that new technologies could undermine secure, second-strike capabilities and, therefore, global strategic stability. They fear that an aggressor could, for example, employ cyber attacks to turn off an enemy’s nuclear command and control, conduct large-scale conventional strikes to blunt an enemy’s nuclear forces, and then use advanced missile defenses to deny any nuclear retaliation. In contrast, other scholars argue that politics trump technology. They maintain that the United States and its democratic allies would employ new technology to reinforce the rules-based system and global strategic stability, while revisionist autocracies would employ new technology in a bid to revise the existing order in ways that might threaten strategic stability. Both perspectives may overstate the importance of these technologies. The Congressional Commission on the Strategic Posture of the United States concludes that these technologies will likely only complement strategic nuclear forces, but not in any meaningful way substitute for them.

US and NATO nuclear strategy

US nuclear deterrence strategy plays a fundamental role in underpinning international peace and security. Unlike Russia and other nuclear powers that build a nuclear force to advance their narrow national aims, US nuclear weapons defend the entire free world. Washington extends nuclear deterrence to more than thirty formal treaty allies in Europe and the Indo-Pacific. More than half of global gross domestic product is protected by US nuclear weapons.

To maintain deterrence in this challenging security environment, the United States, NATO, and other US allies and partners need a strategy capable of deterring and, if necessary, defeating China and Russia simultaneously. The free world has an interest in maintaining peace and stability in Europe and the Indo-Pacific, and it cannot afford to allow strategic deterrence to fail in either region.

To maintain deterrence, the United States and its allies should maintain their long-standing and successful deterrence strategy. The fundamentals of deterrence have not changed. US and NATO policy should strive to persuade potential adversaries that the cost of aggression outweighs any potential benefits, as the adversary perceives it. Deterrence is about holding at risk that which the adversary holds dear. As the 1983 Scowcroft Commission explained, “Deterrence is the set of beliefs in the minds of the Soviet leaders, given their own values and attitudes, about our capabilities and our will. It requires us to determine, as best we can, what would deter them from considering aggression, even in a crisis—not to determine what would deter us.”

Putin and Xi each value their own life and hold on power, respective regime, and national nuclear and conventional military forces. They do not particularly value the lives of their citizens, as we can see from Putin’s bloody war against Ukraine.

Accordingly, US deterrence strategy has long pursued what is sometimes referred to as a “counterforce” targeting strategy. The United States builds a nuclear force capable of holding at risk key elements of enemy leadership, the security structure maintaining the leadership in power, nuclear and conventional forces, and war-supporting industry. The United States does not practice a “countervalue” strategy of intentionally targeting adversary population centers.

There are a number of benefits to this targeting strategy. First, it is more effective for deterrence in that it holds at risk that which the adversary holds dear. Second, it is consistent with the Law of Armed Conflict in that it distinguishes between military and civilian targets. Third, and finally, it allows for the possibility of limiting damage if deterrence fails by blunting an adversary’s strategic force.

The United States and NATO have also pursued “flexible” and “tailored” options in their deterrence strategy. Washington and its allies want options between suicide and surrender. If deterrence fails and an adversary commits large-scale conventional aggression or executes a limited nuclear strike, the Alliance needs options other than full-scale nuclear retaliation or backing down.

As such, the Alliance has always maintained the ability to restore deterrence at the lowest level of escalation. This requires the ability to conduct limited nuclear strikes backed by a range of lower-yield and forward-deployed nonstrategic nuclear weapons.

These fundamentals remain sound. The new more challenging security environment, therefore, does not require the United States and NATO to reinvent deterrence theory. Rather, they need to adjust their strategic posture to address the new threat environment.

Recommendations for US and NATO strategic posture

To address this challenging security environment, the United States and NATO need to update their strategic posture for a two-nuclear-peer threat environment.

  1. Conventional forces: The United States and its allies should build a conventional force posture capable of deterring and, if necessary, defeating China and Russia in overlapping time frames. This contributes to nuclear deterrence. It is unlikely that Beijing or Moscow would launch a bolt-out-of-the-blue nuclear strike. Rather, the most likely scenario for nuclear use would be escalation resulting from a conventional war. By deterring conventional conflict, the United States and NATO can deter nuclear war. If Washington and its allies are unwilling or unable to build a conventional force capable of deterring two major power rivals simultaneously, then they will, like during the Cold War, need to increase reliance on nuclear weapons in their deterrence strategy.
  2. Strategic nuclear weapons: The current size of the US strategic, deployed nuclear weapons force (1,550) was set in 2010. The international security environment has greatly deteriorated since that time, and the deterrent force designed for 2010 is inadequate for the projected future security environment. To address the larger number of targets presented by China’s growing arsenal and to address the possible expansion of Russian nuclear weapons in the absence of the New START Treaty, the United States needs—for the first time since the end of the Cold War—to prepare to increase the size of its strategic deployed nuclear arsenal. The exact number of nuclear weapons required by the United States for the coming security environment can only be determined in a classified setting, but it will be more than 1,550. The United States does not need to immediately increase the size of its nuclear arsenal, but it must take urgent action now to be prepared for an increase in the near future. This includes exercising the upload of additional nuclear warheads on existing land-based and submarine-launched missiles, and planning to buy more modern bombers, submarines, and missiles.
  3. Nonstrategic nuclear weapons: The United States and NATO should develop and deploy nonstrategic nuclear weapons in the European theater. During the Cold War, NATO maintained a range of nonstrategic nuclear weapons to deter Soviet aggression. At the end of the Cold War, NATO greatly reduced this category of weapons and now retains only a couple of hundred gravity bombs deliverable from fighter aircraft. In contrast, Russia possesses thousands of theater nuclear weapons and a wide range of delivery platforms. As such, Russia maintains a significant nonstrategic nuclear advantage that it uses to backstop aggression, including in its war in Ukraine. To address this shortfall, NATO needs to strengthen its nonstrategic nuclear posture with capabilities that are low-yield, forward-deployed, prompt, survivable, and capable of penetrating enemy air and missile defense with high confidence.
  4. NATO’s nuclear posture: The security environment has greatly changed since NATO’s current nuclear posture was designed at the end of the Cold War. NATO strategy documents routinely state that NATO’s nuclear posture is “fit for purpose,” but it is unlikely that a posture designed for the 1990s is “fit for purpose” in the 2020 to 2030 time frame. NATO should commission an internal study to reexamine NATO nuclear posture. The study should consider a wide range of options including additional nuclear capabilities like air- and ground-launched nuclear-armed cruise missiles, and new deployment arrangements, including to NATO’s eastern flank.
  5. Air and missile defense: The United States and NATO should strengthen regional and US homeland air and missile defenses. Integrated air and missile defense systems (IAMD) contribute to deterrence-by-denial. If an adversary fears that an attack may be defeated, then the opponent will be less likely to conduct the attack. In addition, an adversary may believe that only a large-scale attack could overwhelm an IAMD system, deterring limited attacks. A perfect defense against Russia’s nuclear and missile forces is impossible, but also unnecessary. Rather, the United States and NATO can and should build a limited IAMD system capable of defending key targets, such as critical infrastructure, military bases, ports of embarkation and debarkation, and so on. The United States should also make a significant change to its homeland missile defense policy, designing a missile defense system to defend both against rogue states and limited attacks from China and Russia.
  6. Arms control: US and NATO strategic forces policy has long pursued a balanced approach that combines strong deterrence with strong arms control. This overall approach remains sounds. The challenge in the current security environment, however, is that NATO adversaries, Russia and China, are not particularly interested in binding arms control agreements. Russia has cheated on nearly every major arms control treaty it has entered. Moscow has suspended its compliance with the New START Treaty. China refuses to seriously discuss nuclear arms control. It is possible, therefore, if not likely, that when New START expires in January 2026 that there will be no formal arms control agreements among the major powers for the first time since the 1970s. The United States and NATO should develop proposals for, and seek to negotiate, effective arms control for the coming two-nuclear-peer threat environment; however, they should also prepare for a future without arms control. In the first Cold War, effective arms control was only reached after a decades-long arms competition. It is possible that the next round of effective arms control will only arrive after another sustained arms competition.
  7. Emerging technology: The United States and its NATO allies should seek to maintain their innovation edge in the emerging technologies of the twenty-first century. These technologies could strengthen their strategic deterrent capabilities and deny revisionist adversaries a military-technological advantage that they could exploit for destabilizing purposes. Moreover, new technologies may also contribute to arms control by improving capabilities for monitoring verification and compliance. Although difficult, the United States and its NATO allies should lead an effort to negotiate new global norms for the responsible uses of emerging technology.
  8. Risk reduction: In the possible absence of binding limits on the size and composition of the nuclear forces of the major powers, NATO should pursue other risk reduction measures. This could include strategic stability dialogues at the official and track 1.5 levels, crisis communication hotlines, missile launch notification measures, the development of norms of behavior for space, cyberspace, and emerging technology, and other creative measures.
  9. Nonproliferation: The United States and NATO have benefited from an effective nuclear nonproliferation regime that has slowed the spread of nuclear weapons around the world. The Alliance should continue to support the Nuclear Non-Proliferation Treaty and other nonproliferation efforts. Member states should remain steadfast in their objectives of preventing Iran from developing a nuclear weapon and in denuclearizing North Korea.
  10. Prepare governments and publics: Perhaps the contribution most NATO allies can make to strategic stability is to prepare their governments and publics for this third nuclear age. The strong urge in many European capitals to make progress on nuclear reductions is understandable, but also unrealistic and even dangerous for the foreseeable future. We need to educate our publics that near-term efforts to reduce US or NATO nuclear weapons in this security environment will weaken, not strengthen, strategic stability. To truly strengthen strategic stability we need to strengthen our strategic deterrent against revisionist and aggressive, nuclear-armed, autocratic rivals. This was not our choice. We would all prefer to live in a more benign security environment. But this is the world Russia and China are forcing upon us.

About the author

Related content

The Transatlantic Security Initiative, in the Scowcroft Center for Strategy and Security, shapes and influences the debate on the greatest security challenges facing the North Atlantic Alliance and its key partners.

Image: A B-52 Stratofortress bomber aircraft assigned to the 340th Weapons Squadron at Barksdale Air Force Base, Louisiana, takes-off during a U.S. Air Force Weapons School Integration exercise at Nellis AFB, Nevada, November 18, 2021. The B-52 is a long-range bomber capable of dropping or launching a vast array of weapons in the U.S. inventory. (U.S. Air Force photo by William R. Lewis)