U.S. Allies and Adversaries Are Attempting Nuclear Deterrence without Weapons — Will It Work?

Your adversaries and closest allies might not need nuclear weapons to achieve deterrence — they just need you to believe they could build them at any moment.

Nuclear proliferation is once again in the news. Iran is moving exceedingly close to a nuclear weapon. U.S. allies are calling for nuclear weapons with renewed fervor too. On March 7, Polish Prime Minister Donald Tusk said that it was now time to “reach for opportunities related to nuclear weapons.” South Korean leaders have made similar public calls for exploring the nuclear option. These events seemingly suggest we are entering a new era, one characterized by a sharp increase in the pace of nuclear weapons proliferation. Yet recent actions by potential proliferators do not necessarily imply they are bent on arming. Instead, they resemble a strategy I call latent nuclear deterrence.

This strategy, which I detailed in a new book, involves developing the dual-use technology needed to make nuclear weapons without going all the way to a bomb. Countries can then exploit their near-nuclear status to influence the behavior of their adversaries and allies.

Akbar Hashemi Rafsanjani, the former president of Iran, explicitly embraced a latent deterrence strategy when he said in 2005, “once we have mastery of the fuel cycle, all our neighbors will draw the proper conclusion … to dare to attack Iran would be foolhardy.” Other Iranian officials have made similar statements more recently. Meanwhile, U.S. allies are increasingly wondering if they can trust Washington to provide for their security. When this happens, allies may build their own nuclear weapons, a path that France followed under Charles de Gaulle. But most allies don’t ultimately arm. They raise the possibility of nuclear proliferation in hopes that Washington will redouble its alliance commitment.

Will this strategy of latent deterrence work? Many policymakers think so. In 2004, Mohammed El Baradei, the former director general of the International Atomic Energy Agency, said, “If you are really smart, you don’t need to develop a weapon, you just develop that capability. And that is the best deterrence.” In this view, having the dual-use technology needed to make a bomb — commonly called “nuclear latency” — is a substitute for having full-blown weapons.

There is some truth to this view, but the path forward will be challenging for countries seeking influence from a non-weaponized nuclear program. Some states relying on latent deterrence today are better positioned than others to meet the requirements for success.

Varieties of Latent Deterrence

U.S. allies and Iran are seeking to enhance their international influence using nuclear technology. However, they are pursuing different forms of latent deterrence.

Allies are using an approach I call deterrence by proliferation. Here, a country threatens to possess nuclear weapons, not necessarily to use them in an attack. Assuming the target of the threat — in this case the United States — opposes nuclear armament, the prospect of inducing proliferation may lead to more accommodating policies. For example, in 1973, before Spain joined NATO, the Spanish government shared a study with Secretary of State Henry Kissinger indicating that Madrid could build a nuclear weapon quickly given its existing dual-use technology. Spain was essentially saying: Do more to protect us or we will build nuclear weapons. Japan and West Germany pursued this strategy during the Cold War as well. By floating the possibility of seeking nuclear weapons, Poland, South Korea, and other U.S. allies seem to be following this playbook today.

Iran is relying on two other forms of latent deterrence beyond deterrence by proliferation: deterrence by delayed attack and by doubt. Deterrence by delayed attack occurs when a country threatens to carry out belated retaliatory nuclear strikes. A near-nuclear state cannot immediately retaliate with nuclear weapons, but it can swiftly assemble one or more bombs and then use them in retaliation for an invasion or other serious military attack. The above statement by Rafsanjani resembles this kind of threat.

Deterrence by doubt usually happens when a country is extremely close to a bomb. At that point, it can become difficult to know for sure whether it may be nuclear-armed. The possibility that the country could have one or more nuclear weapons could deter others from launching attacks, even if it is in fact non-nuclear. During the early 1990s, the CIA concluded there was a 50-50 chance that North Korea could already have one or two nuclear weapons. This uncertainty may have influenced some U.S. officials as they contemplated military action against North Korea during a crisis over Pyongyang’s nuclear program in 1994. Iran is now at the point where it could conceivably use this strategy, too.

How to Succeed

The conditions for success vary based on whether a country is attempting deterrence by proliferation, delayed attack, or doubt. Yet two things generally help across the board.

The first is possessing the most sensitive nuclear technology: uranium enrichment plants or plutonium reprocessing facilities. These plants allow countries to make fissile material — the most critical ingredient for producing a nuclear bomb. Having enrichment or reprocessing technology, then, makes a country’s timeline to a bomb relatively short, perhaps just a few months. A short timeline makes threats to build, and potentially use, nuclear weapons more credible. If the timeline is too long, the target of the threat might believe that it could escape punishment, since many opportunities to stop the potential proliferator would remain.

A recent book by Tristan Volpe argues that being too close to a bomb makes it difficult for a country to reassure others that it will stay non-nuclear, thereby undermining its international influence. Although I argue that being technologically closer to a bomb is better for deterrence, Volpe’s argument usefully puts the spotlight on the second condition for success: a country seeking to maximize success in latent deterrence must reassure others that it is not bent on arming.

Latent nuclear deterrence is a dangerous game. To pursue this strategy, a country must at least implicitly raise the possibility of future nuclear proliferation or use. Doing so can bring unwanted attention, including preventive military strikes against a country’s nuclear facilities or nuclear armament by rivals, generating an arms race. The U.S. intelligence community recognized this back in 1981 when it concluded that the emergence of latent states “could initiate a process of destabilizing counter-actions.” Iran is no stranger to this risk, as it has faced the prospect of attacks against its nuclear sites since the public revelation of its Natanz enrichment plant in 2002.

The key to mitigating this challenge is to adopt a restrained nuclear program. These programs can include some flirtation with the nuclear option. However, they cannot feature a dedicated weapons program, which I consider to be present when the political leadership has decided to develop the bomb, the weapons program is a high national priority backed by broad domestic support, and there is no intention to reverse course. I classify programs as unrestrained when they meet these conditions.

Countries with restrained programs appear less threatening to others and reduce incentives for countermeasures, like preventive military attacks. These countries also preserve the viability of deterrence proliferation, a strategy that requires perceptions of nuclear restraint. If a national leader believes that a rival is already racing to a bomb there is both a more urgent need to act and less incentive to hold back. Deterrence by delayed attack and doubt can still work if others perceive that a country with enrichment or reprocessing technology is racing to build nuclear weapons. However, because this pathway takes deterrence by proliferation off the table and is more likely to trigger destabilizing counteractions, the combination of this technology and nuclear restraint is more likely to enhance a country’s influence overall.

New evidence in my book, including 20 case studies and quantitative findings from statistical models, supports this idea. Having enrichment or reprocessing technology and a restrained nuclear program can yield several benefits: greater foreign policy alignment with rivals, fewer crises, more U.S. troop deployments to allies, and a lower risk of nuclear armament by adversaries. By contrast, this technology paired with an unrestrained program produces less reliable deterrence of crises and conflict, a risk of preventive military attacks, and arms racing.

Prospects for Jittery Allies

What does this imply about the prospects for U.S. allies to succeed in deterrence by proliferation today?

U.S. allies in East Asia are relatively well positioned for success. Japan meets both criteria: it has a large-scale fissile material production capability and a restrained nuclear program. Nobody thinks that Japan is racing to a bomb today. But everybody knows that it could build one quickly following a political decision, especially if it just wanted a single first-generation weapon. The key question is whether the Trump administration would oppose or welcome a Japanese bomb. President Donald Trump has endorsed Japan getting its own nuclear weapons in the past. If this becomes U.S. policy, deterrence by proliferation would completely lose its bite.

However, the United States is not the only relevant audience for Japan’s latent deterrent. Tokyo has tried to use its nuclear latency to deter China and North Korea, in addition to influencing the United States. Then-vice president Joe Biden did this on Tokyo’s behalf too, telling Chinese leader Xi Jinping that Japan could build nuclear weapons “virtually overnight” if Beijing didn’t help rein in North Korea. Japanese officials have increasingly embraced the idea of latent deterrence against adversaries. Former Defense Minister Satoshi Morimoto said, for example, that Japan’s nuclear latency provides “very great defensive deterrent functions.” Japan’s prospects for success here are strong — maybe better than towards the United States, due to questions about Washington’s opposition to nuclear proliferation.

South Korea is in a less favorable position. Yet, it is one in which latent deterrence could still be viable. Like Japan, South Korea has been able to credibly signal nuclear restraint in recent decades. But unlike Japan, it does not have large-scale enrichment or reprocessing facilities. Seoul’s activities in this area have been limited to laboratory-scale work, and it does not presently have the technology needed to make enough fissile material for one or more bombs. Based on my analysis, laboratory-scale enrichment or reprocessing activities can be helpful for bolstering a latent deterrent, but they are not nearly as effective as having larger-scale plants.

Poland’s prospects of deterrence by proliferation are bleak. It lacks any enrichment or reprocessing capabilities, putting it too far away from a bomb. Poland has plans to build nuclear power plants, but its dual-use nuclear capabilities are currently nascent. Polish officials will therefore struggle to make proliferation threats credible, whether the audience is the United States or Russia.

In NATO, the U.S. allies best positioned for success are Germany and the Netherlands. They currently operate large-scale enrichment or reprocessing plants and are not perceived as racing to a bomb. Other NATO members that operated these facilities in the past — Belgium, Italy, Norway, and Spain — could position themselves for success relatively quickly. Many of the “frontline” states, such as Estonia, Latvia, and Lithuania, are unlikely to find value in a latent deterrent anytime soon. It would not be surprising, though, to see some of these countries embark on plans to expand their dual-use nuclear capabilities in the coming months and years.

Iran’s Latent Deterrent

At least some Iranian officials believe that its latent deterrent has been beneficial. Iran’s former ambassador to the United Kingdom, Seyed Mohammad Hossein Adeli, said in 2007, “Iran would like to have the technology, and that is enough for deterrence.” Five years later, Seyed Hossein Mousavian, an Iranian nuclear negotiator, echoed this view, saying that his country’s dual-use uranium enrichment program was “extremely important for Iran, not only for industrial development, but also as a ‘virtual deterrent.’” What should we expect moving forward?

From a technological standpoint, Iran is well positioned for success. It has a large-scale uranium enrichment program that provides the means to make fissile material for bombs in short order. Tehran’s challenge stems from foreign perceptions of its intentions: Some U.S. and Israeli officials believe that Iran is bent on building nuclear weapons. This has two negative effects for an Iranian latent deterrent. First, it neutralizes the viability of deterrence by proliferation. Second, it exacerbates the perceived threat posed by Iran’s nuclear program, leading to calls for preventive military action.

Iran can still use deterrence by delayed attack or doubt. To do so, it would have to convince potential attackers that its latent forces could survive a disarming first strike. This may be easier to do than it seems on the surface. Locating and destroying relevant infrastructure and materials may be difficult since Iran can disperse, relocate, and hide centrifuges and enriched uranium. If an attack fails to eliminate some of Iran’s fissile material production capacity, it could race to a bomb following the opening salvo. Moreover, it may be increasingly difficult to be certain that Iran is still non-nuclear if it continues to inch closer to a bomb, a path it has followed since the U.S. withdrawal from the Joint Comprehensive Plan of Action in 2018. Israeli diplomat Alon Pinkas hinted at this when he wrote in 2021 that “Iran is already a nuclear state” because of the dual-use nuclear technology it possesses.

Inking Deals with Allies and Adversaries

The Trump administration appears frustrated with U.S. allies, in part because they do not contribute to what it considers to be their fair share of collective defense. Alliance “free-riding” does happen sometimes, as I have shown in some of my research. Yet rhetoric and policies that undermine longstanding publicly articulated U.S. alliance commitments will probably increase discussions about nuclear options. Allies’ movement towards nuclear weapons should be seen as a message to Washington. Reassuring allies through supportive public rhetoric, troop deployments, joint military exercises, and other measures can help keep them non-nuclear. U.S. officials may not want to make deals to reassure or “buy out” anxious allies. However, failing to do so is a recipe for further nuclear proliferation.

Trump says he wants to negotiate a new nuclear deal with Iran and reportedly sent a letter to officials in Tehran to initiate talks. Iran appears skeptical given Trump’s withdrawal from the Joint Comprehensive Plan of Action. In responding to Trump’s letter, Tehran rejected direct negotiations with the United States but raised the possibility of Oman-mediated indirect talks. Trump is considering this proposal. He says he prefers a deal but appears willing to consider attacking Iran’s nuclear facilities if talks fail. How realistic is a new nuclear deal?

U.S. officials can increase the chances of a successful deal by enabling the conditions for successful latent nuclear deterrence. The viability of latent deterrence helped make the Iran nuclear deal possible in 2015. It could play a role this time, too.

This may be politically difficult. It would require allowing Iran to maintain at least some of its uranium enrichment capacity. U.S. officials appear wary of Iran possessing dual-use technology that puts it on the cusp of a bomb. But demanding that Iran permanently shut down all enrichment activities is probably a non-starter in Tehran. To maximize the potential of a latent deterrent, Iran would also need to make clear it has a restrained nuclear program — and U.S. officials would have to perceive it as such. This is a tall order and would require robust reassurance measures, such as the surveillance provisions that were part of the 2015 deal. If there is nothing Iran could conceivably do to convince U.S. officials that it is not bent on arming while still maintaining some enrichment capacity, a new nuclear deal may be dead on arrival.

Conclusion

Latent nuclear deterrence — using nuclear programs without assembled weapons to gain international influence — has been a feature of world politics for decades, and it remains so today. Yet not everyone who embraces this strategy succeeds. The countries best positioned to gain influence without arms are those that have an enrichment or reprocessing capacity and a restrained nuclear program. Combining the most sensitive dual-use nuclear technology with restrained political intentions is a recipe for maximizing the odds of success.

Matthew Fuhrmann is the Cullen McFadden Professor of Political Science at Texas A&M University. He is the author of Influence Without Arms: The New Logic of Nuclear Deterrence.

Image: Midjourney.

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