By Robert Einhorn
Russia’s invasion of Ukraine upended many of the norms and expectations essential to the success of the global nuclear nonproliferation regime.
In his August 1 address to the nuclear Nonproliferation Treaty (NPT) review conference, U.S. Secretary of State Antony Blinken referred to the potentially damaging impact of the invasion: “So what message does this send to any country around the world that may think that it needs to have nuclear weapons to protect, to defend, to deter aggression against its sovereignty and independence? The worst possible message.”1 According to foreign affairs columnist David Ignatius the Russian war “might prove the greatest stimulus to nuclear proliferation in history.”2 Similar concerns are shared by many other experts.3
Such proliferation pessimism in the midst of Russia’s brutal effort to erase Ukraine as an independent state is understandable. Some non-nuclear-weapon states under threat from hostile nuclear powers may reconsider whether they need their own nuclear deterrent to guarantee their security. Moreover, the perception that Russian President Vladimir Putin’s nuclear saber-rattling succeeded in deterring NATO’s direct intervention in the conflict may reinforce the determination of nuclear-armed states such as North Korea to hold on to their nuclear weapons. It also may increase the fears of non-nuclear-weapon states that are potential victims of nuclear power aggression that they could be left without a nuclear protector and forced to fend for themselves.
In theory, the Ukraine experience could incentivize more countries to pursue their own nuclear weapons capabilities, but nuclear proliferation does not occur in theory. It occurs in particular countries, with particular security situations and adversaries, security relationships with friendly states, national priorities, technological and financial capabilities, and domestic balances of political power.
To evaluate the impact of the Russian invasion on real-world prospects for further proliferation, it is essential to focus on particular cases, including the countries often considered possible candidates for reconsidering their nuclear options. When one does that, the outlook for further proliferation does not appear as pessimistic as has been widely assumed.
If any country is likely to “go nuclear” as a result of the war, Ukraine would be a logical bet. Russia’s all-out invasion last February, annexation of Crimea in 2014, and support for pro-Russian separatists in eastern Ukraine were clear-cut violations of the 1994 Budapest Memorandum. That agreement committed Russia, the United Kingdom, and the United States to safeguard Ukraine’s sovereignty and territorial integrity and significantly influenced Ukraine to remove Soviet-era nuclear weapons from its territory and join the NPT as a non-nuclear-weapon state. In a February 19 speech, Ukrainian President Volodymyr Zelenskyy asserted that Russia’s aggression “put in doubt” the package of decisions contained in the memorandum, presumably including Ukraine’s decision to renounce nuclear weapons.4
Nevertheless, for many of the reasons that Ukraine renounced nuclear weapons in the early 1990s and maintained its non-nuclear-weapon status despite Russia’s 2014 encroachments, it is very unlikely to opt for nuclear weapons now. Although Ukraine has a substantial nuclear energy infrastructure, it lacks the specialized facilities needed to produce fuel for nuclear weapons or the weapons themselves. Devoting time and resources to construct those facilities would make little sense when the national priority for years to come will be rebuilding the country in the wake of the war’s devastation.
More fundamentally, Ukraine believes, probably more now than in 1994, that its future is with the West. Even if NATO membership is never in the cards—many Ukrainians and NATO members doubt that it is—Ukraine recognizes that U.S. and European military assistance is essential to its war effort and to defending against future Russian aggression. Moreover, Ukraine is determined to join the European Union and become more integrated economically, politically, and socially with the rest of Europe.
Ukraine knows that embarking on a nuclear weapons development program would alienate its Western partners and put those interests in jeopardy. It could find itself cut off from security assistance and subject to sanctions, including on the civil nuclear cooperation needed to sustain its heavy reliance on nuclear power to meet its energy requirements. Ukraine also knows that an embryonic nuclear weapons program, if detected, could well provide a pretext for a preemptive Russian military attack.
Thus, the likelihood of Ukraine pursuing nuclear weapons development is low and would be even lower if Western security assistance enables the country to achieve a relatively acceptable outcome to the war and if the United States and its allies follow through on their declared intention to strengthen Ukrainian defenses against future Russian aggression.
Frontline NATO States
The frontline states of NATO, mainly Estonia, Latvia, Lithuania, and Poland, might be considered candidates for reevaluating their nuclear options. Putin’s expansive, pre-invasion description of Russia’s geopolitical ambitions, essentially to turn the clock back to the days of the Soviet Union and its sphere of influence, was perceived by those NATO allies as a serious and immediate threat. Since the invasion, they have been on edge about the prospect of Russia expanding the war to their territories and urgently appealed to their NATO partners to bolster their capabilities to deter a Russian incursion.
At their June summit in Madrid, NATO leaders agreed to augment alliance capabilities to defend the frontline states and to “defend every inch of allied territory at all times.”
These force enhancements, the prospect of more in the future, and the renewed solidarity and sense of purpose displayed by NATO countries in response to the Russian invasion should convince the frontline allies that their interests are much better served by relying on NATO’s Article V security guarantee than pursuing an indigenous nuclear weapons capability.
Japan and South Korea
Russian aggression may indirectly affect the security calculations of U.S. allies Japan and South Korea. Neither feels directly threatened by Russia, but they are worried that its attack on Ukraine and its nuclear threats designed to deter U.S. and NATO intervention in the conflict could embolden China and North Korea to act aggressively in the region. They worry that China and North Korea might assume that their ability to strike the U.S. homeland with nuclear weapons would deter the United States from coming to the defense of its allies.
The situations are very different. The United States is not bound by treaty to defend non-ally Ukraine, but is obliged to defend allies Japan and South Korea. Moreover, unlike in Ukraine, the United States stations large numbers of military personnel in both East Asian nations, which ensures that aggression against them would implicate vital U.S. interests and virtually guarantee U.S. involvement in the conflict. Nonetheless, the unsettling Ukraine experience, combined with the threatening nuclear and missile capabilities of China and North Korea and persistent regional uncertainty about the reliability of U.S. security commitments, could increase interest in Japan and South Korea in pursuing their own nuclear deterrents.
In recent years, South Koreans have grown increasingly concerned about the ability of their alliance with the United States to deter North Korea. Political figures, especially from the ruling conservative People Power Party; prominent former officials; and think tank experts have suggested options to enhance deterrence, including the redeployment of U.S. tactical nuclear weapons in South Korea, NATO-like nuclear-sharing arrangements that would enable South Korean pilots to deliver U.S. nuclear weapons in the event of war, and South Korea’s acquisition of its own nuclear weapons capability. South Korean public opinion has long favored indigenous development of nuclear weapons. A recent poll found that 71 percent favored an independent South Korean deterrent, greater than the 56 percent that favored the deployment of U.S. nuclear weapons in South Korea.5
In Japan, the nuclear debate has been more subdued, with the Japanese public opposed to acquiring nuclear weapons.6 Still, the subject is no longer taboo. As in South Korea, questions about the credibility of the U.S. extended nuclear deterrent have led the Japanese strategic community to think seriously about options for strengthening deterrence in a more challenging security environment.
Although support has grown in both countries for reassessing the wisdom of remaining non-nuclear-weapon states, neither is likely to opt for its own nuclear weapons. The Biden administration has done much to reassure the Japanese and South Koreans by giving high priority to strengthening U.S. alliances and reinforcing the U.S. extended deterrent, a sharp contrast to President Donald Trump’s transactional, often dismissive approach to these long-standing allies.
In addition, while continuing to depend heavily on the U.S. nuclear deterrent, these allies have given high priority to increasing their own military spending and boosting their own conventional defense and deterrence capabilities. These national efforts, by enhancing overall alliance deterrence and reassuring citizens of the governments’ ability to defend against growing regional threats, may reduce the perceived need for Japan and South Korea to develop their own nuclear weapons.
Moreover, the strong and skillful leadership displayed by the United States in rallying broad international support for penalizing Russia and assisting Ukraine militarily, even in the absence of a formal alliance with Ukraine, could serve to warn China and North Korea of the risks of aggression and to reassure U.S. allies and partners about the U.S. willingness to stand with them against future aggression.
Another factor working against Japanese and South Korean nuclearization is that acquiring nuclear weapons would not be cost free. A decision by either country to withdraw from the NPT and pursue nuclear weapons development would be a body blow to the global nonproliferation regime and elicit strong international opprobrium. Trading partners could be expected to scale back cooperation in certain strategically sensitive goods and technologies. Among other penalties, international civil nuclear cooperation could be cut off, dramatically effecting Japan and South Korea, which depend on nuclear power for energy.
Both countries would be aware that national nuclear forces and their production and storage facilities would become potential targets of preemptive attack in a crisis, especially in the early stages of nuclearization before survivable retaliatory capabilities are established.
In weighing the costs and benefits of going nuclear, a key factor would be the likely reaction of the United States, which has long opposed the acquisition of nuclear weapons by its East Asian allies. For many years, Japan and South Korea have had good reason to believe that a decision to go nuclear would lead to the weakening of their alliances with the United States and possibly the unraveling of U.S. security guarantees, including the U.S. nuclear umbrella.
With the United States increasingly focused on geopolitical competition with China and Russia, there has been speculation that it would be more tolerant of Japan and South Korea developing nuclear weapons and might even see the move as valuable if it helped tilt the global strategic balance against the United States’ great-power rivals. In that event, Washington might be reluctant to impose security, economic, and other penalties on an ally for choosing its own deterrent.
Depending on the evolution of the international security environment, such a U.S. attitude cannot entirely be ruled out. At least for now, it does not appear likely. The Biden administration seems strongly committed to opposing proliferation, including by its allies in East Asia. It wants to maintain a consistent, global nonproliferation policy and believes that regional stability is better served by continued reliance on the U.S. extended deterrent than by proliferating national nuclear capabilities that would heighten tensions and the risks of nuclear confrontation, intentional or inadvertent, that could involve the United States.
Going forward, the main driver of Japanese and South Korean nuclear decision-making will be the perceived reliability of U.S. security assurances in countering the growing threats from China and North Korea. For now, the Biden administration’s renewed emphasis on strengthening its East Asian alliances and enhancing the credibility of its extended nuclear deterrent, together with Japanese and South Korean conventional defense enhancements, make it unlikely they will opt for their own nuclear deterrent.
Given its precarious geopolitical situation, Taiwan might be expected to revive its interest in acquiring nuclear weapons. China has long been determined to unify the self-governing democratic island with the mainland, by military force if necessary, and President Xi Jinping has stepped up political pressures and military intimidation to hasten that outcome. Taiwan clandestinely pursued a nuclear weapons capability throughout much of the 1970s and 1980s, but it was caught and forced, largely by the United States, to accept constraints on its nuclear activities that effectively crushed its nuclear aspirations.
Taiwanese authorities have drawn parallels between Russia’s invasion of non-nuclear Ukraine, whose legitimacy as an independent state has been challenged by Putin, and an emboldened China’s threat to invade non-nuclear Taiwan, which China views as a renegade province. Like Ukraine, Taiwan faces a mortal threat from a nuclear-armed state and is not the recipient of binding security guarantees from any nuclear power.
Taiwan has plenty of incentive, financial resources, and technical expertise to make another run at nuclear weapons development, but is unlikely to do so. Years ago, it accepted constraints that block its potential paths, including the renunciation of enrichment and reprocessing capabilities, the removal of plutonium-bearing spent fuel, and the shutdown of a research reactor that could be a source of weapons-grade plutonium. After the discovery of Taiwan’s covert program, the United States and the International Atomic Energy Agency (IAEA) pressured Taiwan to accept more rigorous scrutiny of its civil nuclear program, including implementation of an additional protocol to its safeguards agreement, even though Taiwan’s nonstate legal status makes it ineligible to adhere formally.7
Authorities in Taipei also recognize the downsides of seeking nuclear weapons. They know that the United States, their principal benefactor, strongly opposes a nuclear-armed Taiwan, which would radically alter the cross-strait status quo that the United States is determined to uphold. Taiwan’s leaders understand that pursuing their own nuclear deterrent would likely forfeit the substantial increase in political support and military assistance they have received from the Trump and Biden administrations, including after Russia’s invasion of Ukraine. Taiwan’s international political isolation would worsen, and the international trade and investment relationships that are the source of the island’s prosperity could fall victim to sanctions. Not least, China would view a nuclear weapons program as a redline-crossing move intended to ensure Taiwan’s independence and almost certainly trigger a Chinese military response.
Taiwan’s leaders probably understand that, despite President Joe Biden’s apparent personal conviction that the United States should defend Taiwan if it is attacked, the official U.S. position will remain one of strategic ambiguity. Nonetheless, the United States has moved to beef up its military posture in the western Pacific, and a bipartisan group of U.S. senators has introduced the Taiwan Policy Act of 2022 aimed at boosting U.S. security assistance to Taiwan and designating it a major non-NATO ally.8 Taiwan’s leaders probably perceive the U.S. position as evolving in a more reassuring direction, even if it still falls short of a formal guarantee. With U.S. encouragement, Taiwan seems more inclined to take its defense requirements more seriously, to commit the needed funds and political capital to address the growing threat, and to acquire the military and intelligence capabilities most relevant to countering likely scenarios of Chinese aggression.9
Relying on growing U.S. support and stepped-up national defense efforts will be seen by Taiwan’s authorities as a more promising approach to safeguarding the island’s self-governing status than pursuing nuclear weapons.
The non-nuclear-weapon state most likely to seek to join the nuclear club is Iran, although its interest in doing so long predated the Russian invasion and, unlike frontline NATO states in Europe or U.S. allies in East Asia, it does not feel directly or indirectly threatened by Russian aggression.
The Trump administration withdrew from the Iran nuclear deal, formally the Joint Comprehensive Plan of Action (JCPOA), in 2018 and Iran responded with a large-scale buildup of its uranium-enrichment program. Indirect negotiations between the United States and Iran on an agreement to return to JCPOA compliance are at an impasse. Biden administration officials say prospects for a deal in the near term, particularly before the U.S. midterm elections in November, are unlikely.
In the absence of JCPOA revival, Iran could soon have the capability to produce enough weapons-grade uranium to fabricate a nuclear weapon in a matter of days. Reviving the JCPOA and its tight nuclear restrictions would lengthen that “breakout” time to around six months, giving the international community sufficient warning to discover an Iranian breakout and intervene to stop it, if necessary with military force.
An agreement would keep Iran that safe distance from the nuclear threshold for another eight years, but with the JCPOA’s nuclear restrictions scheduled to expire in 2031, a return to the nuclear deal would not permanently close Iran’s nuclear weapons options.
Thus, if the JCPOA is not revived or if it is revived but an extension of its restrictions beyond 2031 cannot be negotiated, Iran’s nuclear program would at some point be unrestricted. In either circumstance, the United States and its partners would have to rely on diplomatic pressures, economic sanctions, and ultimately the threat of preemptive attack to impede Iran’s advance to a nuclear weapons capability.
A nuclear-armed Iran is not inevitable. Iranian leaders may well decide that, in light of the potential economic costs and security risks of building nuclear weapons, their goals would be better served by settling for a threshold nuclear capability, which would give them a future option to acquire nuclear weapons relatively quickly at a time of their choosing. Such a capability could be seen in Tehran as enhancing their regional clout. Alternatively, as many observers predict, Iran may decide that the benefits of actually possessing nuclear weapons are much greater than having a threshold capability. In such a case, however, Iran would still face the obstacle of a few states, especially the United States and Israel, being willing to employ any means necessary to stop it.
At the margin, Iran’s choice might be influenced by the fallout over Ukraine. Although the strengthening of strategic ties between Moscow and Tehran preceded the invasion, it has accelerated since then,10 perhaps giving Iranian leaders the impression that they could count on Russia in withstanding the international pressures that would follow Iran’s nuclear breakout. Whatever Iran decides, it still will be driven fundamentally by the regime’s calculations of its own regional and domestic interests, not by any lessons from the war in Ukraine.
Similarly, Saudi Arabia’s interest in nuclear weapons is independent of the war in Ukraine and based almost entirely on its judgment that arch-rival Iran is determined to be nuclear armed. Saudi Crown Prince Mohammed bin Salman has declared his intention to match a future Iranian weapons capability.11 Contributing to this desire to follow Iran down the nuclear path is a belief shared by several other U.S. partners that the United States is withdrawing from the Middle East and cannot be relied on to protect them from efforts by Iran and its proxies to dominate the region.
Biden’s July trip to Israel and Saudi Arabia was designed in part to counteract that belief and reassure friends that the United States will remain engaged and help them push back against encroachments by Iran. In that connection, the Biden administration has sought to build on the Abraham Accords promoted by the Trump administration and assemble a coalition of Israel and Arab states concerned about the Iranian threat. It has promoted a cooperative missile and air defense and intelligence network to defend against missile, rocket, and drone attacks by Tehran and its proxies.12
Even if the Biden administration makes headway in rebuilding confidence in the U.S. commitment to the region, that is unlikely to dissuade the crown prince from seeking to match an Iranian nuclear capability, given his intense distrust of Iran and his uncertainty about the policies of future U.S. administrations.
Saudi Arabia is likely to have a difficult time catching up with Iran, however. The Saudis have an ambitious plan to build nuclear power reactors, and in negotiations with Washington on a bilateral civil nuclear cooperation agreement, have rejected U.S. proposals that they renounce uranium enrichment and plutonium reprocessing and adhere to an additional protocol to their safeguards agreement. Nonetheless, the kingdom is many years away from having the technical and human infrastructure required to produce nuclear weapons indigenously.
To build the bomb, the Saudis would need large-scale foreign assistance. Several nuclear supplier states, including China, France, Russia, South Korea, and the United States, are eager to sell them nuclear power reactors, but the Saudis would need enrichment or reprocessing facilities to attempt production of nuclear weapons themselves. It is doubtful that Riyadh could find a state possessing such proliferation-enabling technologies that would be willing to provide them or would be willing to sell a fabricated nuclear weapon or its fissile or nonfissile components.
Neither China nor Russia is likely to assist Saudi ambitions by providing proliferation-sensitive nuclear equipment or technology. They do not want a highly destabilizing nuclear arms competition in the Middle East, especially one pitting Saudi Arabia against Iran, their increasingly valued strategic partner.
Proliferation analysts tend to look more toward Pakistan or North Korea as potential nuclear enablers, but with Pakistani nuclear activities under heavy scrutiny in the post-A.Q. Khan era and the government pursuing good relations with Iran and Saudi Arabia, Pakistan is unlikely to provide critical help. Saudi Arabia will not be able to count on North Korea either given that illicit North Korean trading networks and possible Saudi efforts to shop the nuclear black market are likely to be key targets of U.S. and other intelligence and interdiction operations.
The Saudis are highly motivated and likely to persist if the Iranian nuclear threat continues to advance, but they have a steep hill to climb in acquiring a threshold nuclear capability or nuclear weapons, and the probability of succeeding is not high.
The bottom line is that it is premature to write an obituary for the global nuclear nonproliferation regime. Although Russia’s invasion of Ukraine has unnerved the international community, it does not seem to be the proliferation trigger that many analysts predict.
This assessment is based on current circumstances, and circumstances can change. Nonproliferation experts have identified developments that could increase the likelihood of proliferation in the years ahead.13 For example, highly adversarial U.S.-Chinese and U.S.-Russian relations could significantly alter the global nonproliferation landscape. The major powers increasingly could prioritize geostrategic interests over nonproliferation goals. For example, China and Russia might be less inclined to rein in North Korean and Iranian nuclear ambitions that could help offset U.S. power and influence. Already, they are less likely to collaborate with the United States than they did in past negotiations with North Korea and Iran.
In addition, the relative decline in U.S. post-Cold War primacy could weaken Washington’s hand in addressing nonproliferation challenges. Although the United States remains the nonproliferation regime’s leading supporter, its ability to get friends and foes to fall in line behind its nonproliferation policies has diminished. Moreover, despite the Biden administration’s efforts to reassure friends and warn foes that the United States is back as a world leader and committed for the long haul, uncertainty about future U.S. overseas presence and security commitments is likely to persist, given deep domestic divisions at home and the possible return to America First policies.
A Positive Record
The global nonproliferation regime has had a remarkably positive record. In 1992, nine states were believed to possess nuclear weapons (China, France, India, Israel, North Korea, Pakistan, Russia, the UK, and the United States). Thirty years later, despite predictions of a “cascade of proliferation,”14 there are still the same nine nuclear-armed states.
In light of today’s worrisome trends, however, the future of nuclear nonproliferation hardly can be taken for granted. At the same time, the factors that have reinforced the judgment of particular countries to remain non-nuclear, despite the war in Ukraine, will persist. These include the political, economic, and security risks a non-nuclear-weapon state would encounter in pursuing a nuclear weapons program; the financial and technical hurdles some non-nuclear-weapon states would face in embarking on such a program; the security assurances some of these states receive from allied nuclear-armed states; and the recognition by many non-nuclear-weapon states that acquiring nuclear weapons would not be the answer to the actual security challenges they face.
Whatever the likelihood of additional states acquiring nuclear weapons, it is essential to do whatever can be done to make that outcome less likely. Russia’s invasion of Ukraine should be a wake-up call to the United States and other key nations that unless they give high priority to preventing further proliferation by reducing incentives for their friends to acquire nuclear weapons and making it riskier for others to acquire them, the remarkable success of the global nonproliferation regime will be much more difficult to sustain.
1. Antony J. Blinken, Remarks to the nuclear Nonproliferation Treaty review conference, August 1, 2022, https://www.state.gov/secretary-antony-j-blinkens-remarks-to-the-nuclear-non-proliferation-treaty-review-conference/.
2. David Ignatius, “Watching Russia’s Military Failure Is Exhilarating. But a Cornered Putin Is Dangerous,” The Washington Post, March 17, 2022.
3. Michael E. O’Hanlon and Bruce Riedel, “The Russia-Ukraine War May Be Bad for Nuclear Proliferation,” Order From Chaos blog, March 29, 2002, https://www.brookings.edu/blog/order-from-chaos/2022/03/29/the-russia-ukraine-war-may-be-bad-news-for-nuclear-nonproliferation/; Steven Pifer, “Why Putin’s Betrayal of Ukraine Could Trigger Nuclear Proliferation,” Bulletin of the Atomic Scientists, June 1, 2022, https://thebulletin.org/2022/06/why-putins-betrayal-of-ukraine-could-trigger-nuclear-proliferation.
4. Mariana Budjeryn and Matthew Bunn, “Ukraine Building a Nuclear Bomb? Dangerous Nonsense,” Bulletin of the Atomic Scientists, March 9, 2022, https://thebulletin.org/2022/03/ukraine-building-a-nuclear-bomb-dangerous-nonsense/.
5. Toby Dalton, Karl Friedhoff, and Lami Kim, “Thinking Nuclear: South Korean Attitudes on Nuclear Weapons,” Chicago Council on Global Affairs, Lester Crown Center on U.S. Foreign Policy, and Carnegie Endowment for International Peace, February 2022, https://www.thechicagocouncil.org/sites/default/files/2022-02/Korea%20Nuclear%20Report%20PDF.pdf.
6. Rupert Wingfield Hayes, “Will Ukraine Invasion Push Japan to Go Nuclear?” BBC News, March 26, 2022, https://www.bbc.com/news/world-asia-60857346.
7. David Albright and Corey Gay, “Taiwan: Nuclear Nightmare Averted,” Bulletin of the Atomic Scientists, Vol. 54, No. 1 (1998): 54–60.
8. Michael Martina and Patricia Zengerle, “U.S. Senators Introduce Broad Taiwan Bill to Boost Security Assistance,” Reuters, June 17, 2022.
9. Joyu Wang, “In Taiwan, Russia’s War in Ukraine Stirs New Interest in Self-Defense,”
The Wall Street Journal, March 4, 2022.
10. Benoit Faucon, “Iran and Russia Are Cementing an Alliance With Grain, Drones, and Satellites,” The Wall Street Journal, August 27, 2022.
11. “Saudi Crown Prince: If Iran Develops Nuclear Bomb, So Will We,” CBS News, March 15, 2018, https://www.cbsnews.com/news/saudi-crown-prince-mohammed-bin-salman-iran-nuclear-bomb-saudi-arabia/.
12. Nancy Youssef and Stephen Kalin, “U.S. Proposes Helping Israel, Arab States Harden Air Defenses Against Iran,” The Wall Street Journal, June 9, 2022.
13. Eric Brewer, “The Nuclear Proliferation Landscape: Is Past Prologue,” The Washington Quarterly, Vol. 44, No. 2 (Summer 2021): 181–197.
14. “A More Secure World: Our Shared Responsibility; Report of the High-level Panel on Threats, Challenges and Change,” United Nations, 2004, p. 39, https://www.un.org/peacebuilding/sites/www.un.org.peacebuilding/files/documents/hlp_more_secure_world.pdf.
Robert Einhorn, a senior fellow at the Brookings Institution, previously served as assistant secretary of state for nonproliferation in the Clinton administration and the secretary of state’s special adviser for nonproliferation and arms control in the Obama administration.