Key to contain rising revisionist powers---extinction.

Does nuclear modernization promote international security? All the major powers are currently modernizing their strategic nuclear arsenals, and scholars and policymakers are debating the effect of such modernization on international politics. Some argue that nuclear weapons deter a great power war and, therefore, nuclear modernization will contribute to international stability.1 Others claim that modernization programs are fundamentally destabilizing; nuclear weapons are the deadliest weapons ever invented and their continued possession will eventually result in a catastrophic nuclear attack.2

This chapter introduces a third answer to the above question: it depends.

The modernization programs of the United States and its democratic allies at the core of the international system tend to promote international security. On the other hand, the nuclear modernization programs of revisionist autocratic powers intent on challenging the international system tend to threaten global peace and stability. Thus, not all modernization programs are created equal. It is ultimately the underlying geopolitical conditions, and not solely the capabilities themselves, which determine the extent to which modernization programs promote or diminish international security.

Since 1945, the United States has been the leader of a rules-based international order that has brought the world unprecedented levels of peace, prosperity, and freedom.3 U.S. nuclear weapons have provided the security backbone of that order by deterring major power conflict in Europe and Asia.4 Additionally, U.S. extended nuclear security guarantees have protected the entire free world and dissuaded many capable states from developing independent nuclear capabilities. The modernization of U.S. nuclear weapons will therefore continue to reinforce these major sources of geopolitical peace and stability.

Alternatively, Russia, China, and North Korea are opposed to major elements of the existing international system and seek in varying ways to disrupt or displace it. Given their revisionist geopolitical objectives, nuclear modernization in these countries tends to threaten international peace and stability.

Geopolitical intentions guide nuclear strategy, which in turn informs modernization programs. It is therefore essential to account for a state’s position within the international system when evaluating the likely effects of nuclear modernization on international stability.

The rest of this essay proceeds in four parts. First, it explains why U.S. nuclear weapons serve as unique guarantor of international security in the postwar world order. Second, it argues that the United States must modernize its aging nuclear capabilities in order to sustain its longstanding role in promoting global security. Third, it addresses the ways in which revisionist powers seek to use their nuclear modernization programs for destabilizing ends. Fourth, it briefly considers the role of other nations’ nuclear forces, including: Britain, France, India, Israel, and Pakistan. Finally, it concludes with implications for scholarship and for policy.

The U.S.-led, rules-based international order

Following the end of World War II, the United States and its victorious allies built the international system in which we reside today.5 Like past hegemons, the United States ordered an international system to suit its interests. Unlike past hegemons, however, Washington did not seek to rule through formal empire. Rather, it sought to reproduce a variant of its rules-based domestic political system for the global system. This rules-based international order possesses multiple components. First, Washington and its allies established a wide range of international institutions, such as the United Nations, the World Bank, the North Atlantic Treaty Organization (NATO), and the Treaty on the Nonproliferation of Nuclear Weapons, to encourage multilateral solutions to a wide variety of challenges. Second, it sought to correct the protectionism of the interwar years by creating an open economic system defined by the free flow of trade and capital across borders. Third, the United States and its democratic allies have promoted freedom, human rights, and good governance abroad. Lastly, Washington employed its unmatched military might to provide the underlying stability and security which has allowed the overall system to function.

While the system is imperfect and the United States has sometimes disobeyed the rules it helped to write, the rules-based order has nevertheless produced remarkable results. Humanity has been blessed by the absence of great power war for over seventy years. Global standards of living are much higher today than seven decades ago.6 And by the mid-2000s, more people were living under democratic governments than at any time in world history.7

As the world’s most powerful state and the architect of this system, the United States advanced and defended this order through a variety of economic, diplomatic, and military means. An underappreciated but central pillar of this rules-based order, however, has been the U.S. nuclear arsenal. U.S. nuclear weapons have provided the backbone for the underlying security element of the global system.

U.S. nuclear weapons and great power peace

U.S. nuclear weapons contribute to global stability by deterring great power war. U.S. nuclear weapons have deterred revisionist autocratic powers, such as the Soviet Union during the Cold War and Russia, China, and North Korea today, from attacking U.S. allies in Europe and Asia.

Scholars have long appreciated the role of nuclear weapons in deterring war and contributing to the long period of great power peace. Indeed, much social science scholarship credits the nuclear revolution with transforming international politics and making large-scale war among the major powers unthinkable.8

What much of this literature ignores, however, is the unique role played by American nuclear weapons. Unlike other nuclear powers that seek to deter attacks on themselves only, the United States aims to deter attacks against the entire free world.9 The United States extends deterrence to over thirty formal treaty allies, including twenty-eight members of NATO, South Korea, Japan, Australia, and arguably others. The U.S. policy of extended deterrence provides geopolitical stability in Europe and Asia, the two most important geostrategic regions on the planet and the home of all the major nuclear powers.

As a status quo power and leader of the international system, the United States has had little interest in or incentive to use military force to revise the territorial status quo in Europe or Asia. Following the end of World War II, for example, the United States’ immediate goal was in setting up independent governments in defeated countries, allowing free elections, and returning home.10

The Soviet Union, on the other hand, had an explicit goal of spreading Marxist revolutions to other nations in Europe and around the world. It established puppet states under Moscow’s control in the territories it occupied in Eastern Europe. It employed military force, in Hungary in 1956 and Czechoslovakia in 1968, in order to force these states to remain in the Soviet camp. The Soviet Union also attempted to use military coercion in a failed bid to wrest control of Berlin from the West in a series of crises during the late 1950s and 1960s. In Asia, Moscow gave the green light to North Korea to invade its Southern neighbor and initiate the Korean War.11 These are only the major examples of Soviet militarized revisionism during the Cold War.

In the face of this threat from the Red Army, the United States remained in Europe at the behest of its allies to deter Russian invasion. In order to counter the Soviet Union’s conventional superiority in Europe, the United States and NATO relied heavily on nuclear deterrence.12 U.S. nuclear weapons and the requisite resolve to defend allies were critical to forcing Moscow’s submission in the Berlin Crises and to deterring war in Europe. In addition, the United States became more deeply involved in Asia, intervening militarily in Korea and in the Taiwan Straits to prevent communist forces from invading or threatening their neighbors.13 In sum, during the Cold War in Europe and Asia, the Soviet Union’s foreign policy was largely oriented toward revising the status quo, while the United States generally employed force, including nuclear deterrence, in order to uphold it.

Similarly today, Russia, China, and North Korea express their displeasure with the territorial status quo in their respective regions.14 Russian President Vladimir Putin refers to the collapse of the Soviet Union as “the greatest geopolitical catastrophe of the 21st century” and longs to re-establish a “greater-Russia.”15 He has been clear about his interest in re-establishing a sphere of influence in Eastern Europe and he has already invaded two of his neighbors, Georgia and Ukraine. China has also declared a long-term intention to redraw the map of Asia to incorporate Taiwan and it has begun taking contested territory in the South China Sea through military coercion and gray-zone tactics. North Korea has engaged in repeated bouts of aggression against South Korea and Seoul’s American ally over the decades. It initiated the Korean War and seized the U.S.S. Pueblo during the Cold War. In recent years, Pyongyang has sunk a South Korean warship and shelled a South Korean island.

U.S. democratic allies in Europe and Asia consistently call upon the United States to maintain a robust nuclear strategy and posture in order to deter possible aggression from these autocratic and revisionist powers. For example, when U.S. President Obama considered the adoption of a nuclear No First Use Policy at the end of his term, U.S. allies resisted.16 Largely in response to allied demands, the United States agreed to keep the nuclear option on the table to deter conventional aggression. It has also developed nuclear capabilities, including the supplemental, low-yield capabilities called for in the 2018 U.S. Nuclear Posture Review, with the explicit goal of extending deterrence and reassuring allies.17

Therefore, it is true that nuclear weapons have deterred great power war for over seventy years, but it is important to consider whose potential aggression has been deterred. If nuclear weapons were to be un-invented or nuclear deterrence to fail, any ensuing aggression would most likely be conducted, not by the United States, but by Moscow, Beijing, or Pyongyang against their regional neighbors. It is specifically U.S. nuclear weapons that are the most important element for keeping the peace in Europe and Asia.

U.S. nuclear weapons and nonproliferation

The United States has also contributed to the security of the rules-based international system by halting the spread of the world’s most dangerous weapons. Once again, in this domain, U.S. nuclear weapons have been central to these efforts.

As the most powerful state in the international system and the leader of the rules-based order, the United States possesses a strong interest in preventing other nations from acquiring nuclear weapons.18 Washington played a unique role in establishing the major institutions of the nuclear nonproliferation regime, including the Treaty on the Nonproliferation of Nuclear Weapons (NPT).19 Some theorists, like Kenneth Waltz, argue that horizontal proliferation yields greater systemic stability and that Washington could benefit from slow and selective nuclear proliferation, but there are many risks to the spread of nuclear weapons, especially for the world system’s leader.20 Accordingly, this “proliferation optimism” argument has never found favor in the corridors of power.21

To support its goal of preventing the spread of nuclear weapons to allied states, the United States has provided these states with extended deterrence. Washington struck a bargain with allies: refrain from building your own nuclear weapons and we will protect you with U.S. nuclear weapons. As stated above, the United States currently extends its nuclear umbrella to over thirty formal treaty allies and arguably others. Without these efforts at extending deterrence to assure allies, it is likely that at least several other U.S. allies would possess independent nuclear capabilities today. U.S. assurance efforts were essential to eliminating nuclear weapons ambitions in West Germany in the early days of the Cold War, and South Korea and Taiwan in the 1970s.22 Studies employing statistical analysis have shown that, “States receiving security guarantees from nuclear-armed superpower allies are only 22 percent as likely to explore nuclear weapons as those who do not, 13 percent as likely to pursue them, and 15 percent as likely to acquire them in a given year, conditional on their not having done so previously.”23

To make this extended deterrent guarantee more credible, Washington sometimes goes so far as to deploy U.S. nuclear weapons on the territory of its allies. This forward-deployed American nuclear power has been referred to as a wedding ring to its allies, providing a visible symbol of America’s security commitment.24 An empirical study on the link between forward-deployed nuclear weapons and nonproliferation found that forward-deployed nuclear weapons have a perfect track record in preventing nuclear proliferation. Never has a country with U.S. nuclear weapons on its soil developed independent nuclear capabilities.25

To be sure, U.S. attempts at nonproliferation have occasionally failed. In the early stages of the Cold War, U.S. allies Britain and France chose to build independent nuclear arsenals, despite Washington’s preferences to the contrary. Still, the small number of nuclear-armed states today is a fantastic achievement relative to pessimistic proliferation expectations of the mid-twentieth century. And it is very likely that there would be many more nuclear powers in the world today without U.S. efforts at extended deterrence and assurance.

U.S. nuclear security guarantees remain critical in the current security environment to stop the spread of nuclear weapons. With newfound questions about America’s commitment to the security of its allies, there are renewed discussions in Berlin about whether Germany should consider building its own nuclear weapons.26 A majority of the public in South Korea support Seoul going nuclear under uncertain conditions.27 And analysts predict that a weakening of the U.S. nuclear umbrella could lead to proliferation among U.S. allies, including Japan, Poland, and perhaps other states.28

In contrast, other nuclear-armed powers have played a less central role in preventing the spread of nuclear weapons. Indeed, these revisionist and autocratic states have occasionally gone so far as to use their nuclear capabilities to intentionally export the bomb to other states, fueling the spread of nuclear weapons.29 For example, the Soviet Union aided China in developing a nuclear program from 1958 to 1960 to increase the power of the communist bloc relative to the United States. Russia considered exporting a uranium enrichment plant to Iran in 1995 before Washington intervened and pressured them to cancel the transaction. China aided Pakistan due to mutual rivalry with India. Beijing also transferred sensitive nuclear technology to Iran, Algeria, and other countries as well. While Pakistani scientist Abdul Qadeer Khan created a proliferation network which enabled North Korea, Iran, and Libya to acquire sensitive nuclear technology as part of constructing an alliance of “strategic defiance” against the United States and its allies.30 In recent years, Pyongyang has become a nuclear exporter, helping Syria to build a heavy-water reactor before it was destroyed in an Israeli air strike in 2007. All of these countries remain at risk of exporting sensitive nuclear technology in the future, intentionally fueling proliferation in a bid to advance their revisionist aims.

Some have argued that by possessing a robust nuclear arsenal, the United States instigates the spread of nuclear weapons to additional countries, but this is incorrect. They aver that the continued maintenance of an American nuclear arsenal sets a dangerous precedent, undermines the NPT, and encourages other countries to build nuclear weapons. These arguments are plausible at a superficial level, but closer investigation reveals that they are unfounded.31 States build nuclear weapons for a wide range of security, economic, and normative reasons, but aping the behavior of the United States is not among them. Moreover, there is no correlation between the size of the U.S. nuclear arsenal and the probability that other states explore, pursue, or acquire nuclear weapons.32

In sum, U.S. nuclear weapons also contribute to the security of the rules-based system by reinforcing the nonproliferation regime and preventing the spread of nuclear weapons.

The imperative of U.S. nuclear modernization

United States’ nuclear weapons have provided for international security and stability for the past three-quarters of a century, but, if they are to continue to play that role in the future, then they must be modernized.

The U.S. strategic nuclear forces consist of a triad of delivery vehicles: 1) submarine-launched ballistic missiles (SLBMs) deployed on ballistic missile submarines (SSBNs); 2) intercontinental ballistic missiles (ICBMs); and 3) strategic bombers (including the B-2 and B-52) carrying gravity bombs and airlaunched cruise missiles (ALCMs).

These capabilities are aging, however, and must be updated. The OHIO-class SSBNs entered service in the 1980s and 1990s and were originally designed for a 30-year service life. Their service life has already been drawn out to 42 years and further extension is impossible.33 There are only so many times a submarine can withstand the intense pressures of submerging and resurfacing, and relying on these old boats puts the life of the crew at risk.

For the land-based leg, the Minuteman III ICBMs were first deployed in 1970, and they were meant to have a 10-year service life. This service life has been extended multiple times, but the United States cannot continue to rely on this capability beyond 2030.34

Turning to the air leg of the triad, U.S. ALCMs are now 25 years past their expected design life.35 The United States also needs to ensure that its stealth bombers can continue to penetrate current and future enemy air defense systems.

Beyond the delivery systems, the underlying nuclear command, control, and communications (NC3) system is also three decades old and is vulnerable to new space and cyber threats.36 Lastly, the warheads themselves are aging, as many were built in 1976, 1978, 1980, and 1988. These warheads require life extension programs for continued survival.37

In sum, U.S. nuclear weapons were built at the end of the Cold War in the 1970s and 1980s. If you drive a car, it is likely that it was not built in the 1970s or 1980s. And, if it was, then it is not likely very reliable. As long as the United States possesses a nuclear deterrent, it must ensure that it is safe, effective, and reliable. This can only be achieved with modernized capabilities.38

In 2010, then-U.S. President Barack Obama laid out a plan to modernize America’s aging nuclear arsenal over the next thirty years. He called for modernizing each leg of the nuclear triad. In 2031, the new Columbia-class SSBN will begin to replace the Ohio fleet, while the Department of Defense will research a potential replacement to the D5 SLBM.39 The Department of Defense has also launched the Ground-Based Strategic Deterrent (GBSD) program to modernize 450 ICBM launch facilities and field 400 new ICBMs to replace the Minuteman III, beginning in 2029.40 Meanwhile, in order to improve the survivability of the air-based leg in the face of sophisticated enemy air defenses, the U.S. will replace the B-2A with the new B-21 Raider stealth bomber in the mid-2020s. It is also replacing the ALCM with the long-range standoff (LRSO) weapon, and it is modernizing the B61 gravity bomb.41 Simultaneously, the Department of Defense is planning NC3 advancements for improved command and control, as well as coordination with the Department of Energy to extend the service life of the warheads.42

President Trump decided to continue with Obama’s modernization plans in his Nuclear Posture Review, released in 2018.43 In addition, the Trump administration called for capability “supplements” to deal with the threat of Russian nuclear “de-escalation” strikes.44 These low-yield nuclear weapons include installing a low-yield warhead on a small number of SLBMs and the resurrection of a nuclear sea-launched cruise missile.

These modernization plans have strong bipartisan support with senior defense officials on both sides of the aisle attesting to the need for these capabilities.45 Nevertheless, some analysts have questioned the desirability and feasibility of U.S. nuclear modernization.46 Some have argued that U.S. nuclear modernization is too expensive. The Congressional Budget Office (CBO) estimates that the cost of nuclear modernization over the next thirty years will come to over $1 trillion. Critics argue that this is unaffordable and this money could be better spent on other priorities. While $1 trillion is certainly a large number, to put it in perspective, it comes to roughly 5–7% of the U.S. defense budget. Is 5% too much to spend on nuclear weapons? Several recent U.S. secretaries of defense have claimed that nuclear deterrence is the most important mission of the U.S. Department of Defense. So, put another way, is 5% too much to spend on the organization’s highest priority mission? Reasonable people can disagree, but to many this seems to be a good value. Indeed, nuclear weapons have traditionally been prized because they are more economical than conventional weapons.47 As Obama’s Secretary of Defense Ash Carter pithily put it, “nuclear weapons don’t actually cost that much.”48

Other critics of U.S. modernization plans charge that building a new generation of nuclear weapons will fuel an arms race with Russia and China.49 But this is incorrect. Russia and China are already modernizing their forces, and this is occurring irrespective of decisions made in Washington. Indeed, Russia is finishing a modernization cycle and is building new, exotic nuclear weapons, such as a nuclear submarine drone, that have never been contemplated in Washington. When Secretary Carter was asked if U.S. nuclear modernization was stimulating an arms race, he replied, “we know they aren’t having that effect, because the evidence is to the contrary.”50 Moreover, U.S. modernization may actually dissuade arms races, as potential rivals realize they have little hope of achieving nuclear parity with or superiority over the technologically-sophisticated United States.

Finally, some claim that U.S. nuclear modernization plans are inconsistent with its commitments under the NPT to work toward eventual nuclear disarmament. According to this argument, U.S. modernization will cause nuclear proliferation, but this is also incorrect.51 President Obama took good faith steps toward reducing reliance on nuclear weapons, but, as he did so, Russia, China, and North Korea went in the opposite direction, expanding and modernizing their arsenals. Disarmament advocates often harangue Washington, London, and Paris because they know these democracies will listen to their complaints, but they are barking up the wrong tree. If they want to make progress on disarmament, the real obstacle is Moscow, Beijing, and Pyongyang. If other nations up nuclear weapons, Washington would almost certainly join them. So long as these other nations have nuclear weapons, however, the United States needs to possess a robust nuclear deterrent. Moreover, as argued above, doing so reinforces global nonproliferation, by giving U.S. allies the incentive to forego independent nuclear arsenals. Meanwhile, the United States continues to make progress toward nuclear disarmament in other ways with new initiatives to “create the conditions” for future disarmament.52

In sum, U.S. nuclear modernization is necessary for the continued effectiveness of the U.S. nuclear deterrent. Moreover, such measures are affordable and consistent with America’s longstanding disarmament goals.

The threat posed by Russian, Chinese, and North Korean nuclear modernization

Not all modernization programs are created equal. The effect of a state’s nuclear modernization on international security depends upon that state’s objectives and strategy, in accordance with its broader geopolitical disposition. Russia, China, and North Korea are revisionist states dissatisfied with the prevailing status quo. Their broader strategies seek to disrupt or displace the U.S.-led order, and thus their defense capabilities, including nuclear weapons, are oriented toward these destabilizing objectives. Nuclear modernization programs in Moscow, Beijing, and Pyongyang, therefore, tend to undermine international security and stability.

Russia

Russia seeks to disrupt the rules-based international order.53 Under President Putin, Russia has sought to reassert itself as a global great power and to ensure that any major international security issue cannot be decided without Russia at the table. In addition, it seeks to carve out a sphere of influence in Eastern Europe at the expense of the security and sovereignty of its neighbors. It views the spread of the U.S. alliance system and of democratic forms of government as a fundamental threat to the existence of its regime.54 Consequently, it seeks to exploit Western vulnerabilities in order to divide democratic nations within themselves and against each other. To achieve these objectives, Russia employs a “hybrid” or “new-generation warfare” military strategy that combines activities across the full spectrum of conflict, from information operations at the low end to nuclear coercion at the high end.55

The nuclear component of this broader grand strategy is designed to deter NATO from intervening in Russia’s sphere of influence, to coerce neighboring states, and to divide NATO allies against each other.56 In recent years, Russia has increased reliance on nuclear weapons in its strategy.57 Russian leaders have made explicit nuclear threats and have postured and exercised nuclear forces in ways we have not seen since the Cold War. During the Russian invasion of Ukraine, for example, Russian President Vladimir Putin said that “Russia is one of the leading nuclear powers,” and that “it is best not to mess with us.”58 He also put nuclear weapons on alert and moved them into Kaliningrad and Crimea. The message was clear: if the West interferes with Russia’s attempts to use force against its neighbors, the result could be nuclear catastrophe.

The most dangerous component of Russian nuclear strategy is the so-called “escalate-to-de-escalate” doctrine.59 This is simply the idea, widely acknowledged by Russian experts, that Russia will rely on nuclear weapons, including limited nuclear strikes, to offset the conventional superiority of the United States and NATO. This strategy sounds reasonable enough if it were only a defensive strategy to defend the Russian homeland from invasion. The concern is that, like in Ukraine, it will be used as a nuclear backstop to bolster future conventional aggression. Russia could invade a NATO member and then use threats of early nuclear escalation to deter a unified NATO response. Short of invasion, it can continue to use the threat for quotidian nuclear coercion of NATO members over foreign policy decisions of which it disapproves, such as regional states hosting NATO military capabilities.

To support this strategy, Russia is modernizing its nuclear arsenal. It is currently finishing a modernization cycle of its strategic nuclear forces. The Kremlin is building a new generation of non-strategic nuclear weapons, expanding its asymmetric advantages over NATO in this space, and giving credibility to its “escalate-to-de-escalate” approach.60 Finally, it is developing exotic nuclear weapons, including nuclear-armed hypersonic glide vehicles, nuclear-powered nuclear cruise missiles, and nuclear-armed submarine drones.61 The latter is designed as a system of pure terror to hold at risk Western port cities with the threat of a stealthy, large-yield, and highly radioactive strategic attack. These weapons contribute to Russia’s strategic goals of weakening and terrorizing the free world and, as such, they undermine global security and stability.

China

While Russia is the more dangerous near-term threat, China is the greater threat to the global order over the long term. Russia can only disrupt the rules-based order, but China may seek to displace it. China endeavors to gradually replace the United States as the global hegemon by 2049.62 The effort begins regionally in Asia where Beijing seeks to expel the United States as a regional power and establish itself as the region’s hegemon. Globally, China is expanding its political and economic influence in every region of the world through its Belt and Road Initiative (BRI) and Made in China 2025 plans.63 Its state-led capitalist approach seeks to prey on the rules-based economic order at the expense of open market democracies. It is also consciously or unconsciously exporting this state-led capitalist model and seeking to make the world safe for autocracy. Therefore, the rise of China is a profound threat to the rules-based order.

China supports this strategy with an ambitious military modernization program. In East Asia, its anti-access/area denial (A2/AD) approach seeks to undermine U.S. power projection capabilities and enable China to pursue territorial claims in the East and South China Seas, while providing coercive leverage vis-à-vis other regional actors.64 In recent years, the balance of power in Asia has shifted and many question the ability of the United States to defend longstanding allies.65 China is also expanding its global military footprint with overseas bases and military exercises in other world regions.

China is also building nuclear forces designed to contribute to these revisionist aims. While China claims to desire only a “lean and effective” deterrent, it has gradually expanded and modernized its forces in recent years.66 Beijing is clearly attempting to develop a greater ability to hold the U.S. homeland at risk, to increase U.S. vulnerability to a large-scale nuclear exchange, and to deter U.S. military action, including in defense of its allies. In the past decade alone, the number of Chinese strategic nuclear weapons that could reach the continental United States has more than doubled. And U.S. intelligence has recently estimated publicly that China’s nuclear arsenal will at least double again in the coming decade.67 In addition to its strategic forces, China possesses a large stockpile of medium- and intermediate-range missiles that are capable of delivering nuclear weapons.68 These capabilities contribute to China’s A2/AD strategy and could be used to blunt U.S. and allied military forces in their attempts to defend against possible Chinese aggression. While China espouses a formal nuclear No First Use Policy, Chinese experts acknowledge that there is a narrow range of contingencies, such as a major war with the United States in East Asia, in which China might very well use nuclear weapons first. In the future, China may leverage its substantial resources to sprint to nuclear parity, potentially igniting an arms race with the United States and undermining U.S. extended deterrence and assurance in Asia.

North Korea

Relative to the Russian and Chinese great powers above, the rogue North Korean regime is not as threatening to the very fabric of the current international order. Still, North Korea’s nuclear program is a challenge to the rules-based order. Pyongyang has flagrantly violated the nonproliferation regime and its weapons threaten the security of the free world.

Scholars debate North Korean goals. Some argue that North Korea only wants to defend its brutal totalitarian regime from external intervention; others maintain that Pyongyang is pursing the more aggressive and revisionist goal of eventually reuniting the Korean peninsula under its own rule.69 Regardless, North Korean behavior threatens almost every aspect of the rules-based order. It has repeatedly engaged in armed aggression against its neighbors from initiating the Korean War in the 1950s to sinking a South Korean warship in the 2010s. It cheats on global economic rules engaging in currency counterfeiting and black market smuggling activities. It also conducts massive human rights abuses at home.

North Korea’s military strategy seeks to retain the capability to deter external invasion and, if necessary, to fight a full-scale war on the Korean Peninsula. North Korean nuclear capabilities contribute to these goals. It is publicly estimated that North Korea has the ability to deliver close-range, short-range, and medium-range missiles to U.S. allies and bases in Asia, while possessing enough fissile material to build between 30 and 60 nuclear warheads.70 In addition, it is on the verge of developing an ICBM capability to hold the U.S. homeland at risk with the threat of nuclear war.71

While some hope that the international community may be able to negotiate the denuclearization of North Korea, it seems more likely that North Korea will remain a nuclear power for the foreseeable future. If North Korea’s nuclear modernization continues, it will possess a more reliable means of threatening nuclear war against the United States and its allies at the core of the rules-based order. North Korean nuclear weapons may also act as a shield to external intervention, deterring the United States and incentivizing Pyongyang’s aggression against South Korea or Japan. North Korea’s nuclear weapons may also weaken U.S. extended nuclear deterrence and assurance, possibly persuading Tokyo and Seoul to reconsider their nuclear options. More broadly, North Korean possession of nuclear weapons undermines the NPT. North Korea may decide to once again export dangerous nuclear or missile technology. Pyongyang’s nuclear possession may create a dangerous precedent as other nonnuclear nations hope to follow the same path of cheating on the NPT, building nuclear weapons, and ultimately being welcomed as de facto members of the nuclear club.

In sum, Russia, China, and North Korea are autocratic, revisionist challengers to the rules-based international order. As such, their nuclear programs threaten core pillars of the system of global stability and security that has reigned for the past several decades. In short, Russian, Chinese, and North Korean nuclear modernization programs undermine global stability and security.

The role of other nations’ nuclear forces

To this point, we have reviewed the effect of the modernization programs of the United States and its adversaries, but what about the nuclear programs of other nations? This list of nuclear-armed powers includes America’s nuclear-armed allies, Britain and France, and the three nuclear-armed states outside of the NPT framework: Israel, India, and Pakistan.

Like the United States, Britain and France have been status quo actors at the core of the Western liberal order since the end of World War II. Therefore, British and French nuclear weapons have, on balance, done more to reinforce, rather than undermine, sources of global stability. These allied nuclear forces have bolstered the capabilities of the Western alliance, thereby increasing its credibility and demonstrating alliance burden-sharing. Britain and France can deter direct attacks on their homeland. Nuclear weapons in these two nations also complicate Russia’s nuclear targeting and make it possible that Russia will suffer a nuclear attack even if it succeeds in de-coupling America’s nuclear weapons from the security of Europe.

However, British and French nuclear weapons have not had a comparable effect on global security. Due to America’s global power projection capabilities and its vast international commitments, U.S. nuclear weapons have been more influential in underwriting European and global stability. As Albert Wohlstetter argued decades ago, at the end of the day, the nuclear balance in Europe rests primarily on U.S. and Russian nuclear arsenals.72

Moreover, while the United States was working hard to stop nuclear proliferation, France had a troubling history of using its nuclear capabilities to fuel horizontal proliferation. During the Cold War, France provided sensitive nuclear assistance to nonnuclear states, such as Israel and Pakistan.73 Fortunately, France’s nonproliferation policies have greatly improved since that time.

Britain and France are also undergoing their own nuclear modernization efforts and these capabilities will continue to make positive contributions to nuclear deterrence in Europe. It is ultimately the United States, however, which will continue to bear the greatest responsibility for using its nuclear weapons to deter great power war and halt the spread of the world’s deadliest weapons.

India, Pakistan, and Israel are three states that never signed the NPT and then went on to build nuclear weapons. Unlike the other nuclear-armed states reviewed above, these states sit at the periphery of the U.S.-led global order. None of these states are formal U.S. allies, but they are not sworn enemies either. Washington, therefore, does not have a formal obligation to extend nuclear deterrence to these states and these states are not mentioned in the U.S. NPR as possible targets for U.S. nuclear weapons.

Israel is a democracy and a close, although not formal, American security partner. The United States failed in its bid to prevent Israel from developing nuclear weapons in the 1960s. Israel was, however, the repeated victim of conventional aggression by its conventionally superior and autocratic Arab neighbors in the past and its nuclear program has deterred subsequent invasions and generally contributed to Middle Eastern stability. Unlike Iran’s advancing nuclear program today, Israel’s nuclear weapons did not spur other regional states to develop their own nuclear weapons in response.

Nuclear programs in India and Pakistan are also contrary to the global nonproliferation order due to their acquisition outside of the NPT framework and because of a series of subsequent, dangerous nuclear crises in South Asia. The United States has maintained good relations with both India and Pakistan, but the orientation of these states may be shifting in this new era of great power competition. The Chinese-Pakistani strategic partnership seems to be deepening. And India is cooperating more closely with the United States and its democratic allies in Asia as a counterbalance to China’s growing power. If these trends continue, India’s nuclear forces may increasingly serve on balance to reinforce the sources of stability in the prevailing global order. While we can hope that Pakistan does not use its nuclear forces to complement China’s revisionist ambitions.

Still, the existence of three nuclear powers outside of the NPT framework is somewhat problematic for efforts to develop a global, rules-based nonproliferation regime and there have been discussions in Washington about how best to mainstream these programs into the broader rules-based nuclear order.

Conclusion

Does nuclear modernization promote international security? This chapter argues that it depends. Previous scholarship has focused too narrowly on whether the technology itself is inherently stabilizing or destabilizing, but we argue that we can only make sense of the technology when it is situated within its proper geopolitical context. Different actors with different goals use the same technology in different ways. The status-quo-oriented United States has sought to create, advance, and defend the rules-based international order that has governed the global system since 1945. Thus, its nuclear modernization program tends to promote this overall system of international stability and security.

Several autocratic revisionist actors, on the other hand, are threatened by this rules-based system and believe that it does not reflect their interests and priorities. Russia, China, and North Korea are autocracies that are dissatisfied with significant aspects of the reigning order. Accordingly, they are pursuing strategies to revise the international status quo. Their military postures are oriented toward disrupting the current global order, and it is therefore likely that their nuclear modernization programs will diminish international security and stability.

This argument has scholarly and policy implications. Scholars should move beyond abstract discussions about whether nuclear weapons (or modernization programs) are stabilizing or not and focus more on the important variation caused by the strategies of weapons possessors. States use nuclear weapons in different ways and this has implications for how nuclear weapons affect international politics. Current political science models seek to understand the likely effects of nuclear acquisition in Iran, for example, by conducting quantitative analysis of all instances of past proliferation.74 But aggregated data that contains information about U.S., British, and French behavior with nuclear weapons will likely be misleading in attempting to understand how a nuclear Iran will act. Like the revisionist autocracies reviewed above, Iran is another power with a foreign policy objective of resisting the United States and the prevailing international order. It is likely, therefore, that China or North Korea are more accurate models for imagining the behavior of a future nuclear-armed Iran.

In the realm of policy implications, we conclude that the United States must follow through on its modernization plans. U.S. nuclear weapons play a unique role in protecting the free world and preventing the spread of nuclear weapons. The vast majority of states in the international system have a strong interest in the continued salutary effects of a robust U.S. nuclear deterrent.