For decades, nuclear deterrence has dominated interactions between nuclear-armed rivals, as seen in the tense standoffs between the United States and Russia, and between India and Pakistan. This nuclear equilibrium has contributed to regional and international stability. Yet, a critical question arises: How can non-nuclear states establish credible deterrence against nuclear-armed adversaries?
With North Korea possessing nuclear weapons and its neighbour South Korea lacking such an arsenal, the issue of South Korea’s deterrence against Pyongyang has grown increasingly pertinent. This situation highlights the broader inquiry into how non-nuclear states can effectively deter nuclear threats. In the following lines, we examine several strategies and international models that illustrate approaches to this challenge.
1. Extended Nuclear Deterrence
Extended deterrence, primarily associated with the United States, involves Washington providing a “nuclear umbrella” to protect its non-nuclear allies from nuclear-armed adversaries. Through this policy, the United States aims to reassure over 30 allies and partners that it would come to their defence, potentially even employing nuclear weapons if they were attacked. Successive US Nuclear Posture Reviews in 2010, 2018, and 2022 have reiterated this commitment, framing it as a way to prevent nuclear proliferation; allies secure under the US umbrella may feel less compelled to pursue nuclear capabilities themselves. Japan, for example, considers the US nuclear umbrella integral to its national security in its strategic documents.
However, a key test of extended deterrence is the credibility of the protecting power’s willingness to act. Allies may question whether Washington would truly risk nuclear escalation on their behalf, especially if it endangers US territory. This uncertainty led France to develop its own nuclear arsenal, opting for self-reliance in its defence. Likewise, potential adversaries might doubt the resolve of a nuclear guarantor, especially if their aggression risks sparking a nuclear strike against the protecting state. To address this concern, non-nuclear allies sometimes formalise alliances with nuclear powers or host their protective forces, as Russia has done by stationing tactical nuclear weapons in Belarus as a deterrent against Ukrainian or Western aggression.
On the other hand, some US analysts argue that extending the nuclear umbrella might entangle Washington in unwanted conflicts, as the protected states may take more aggressive stances, assuming US backing. This could inadvertently increase the chances of a nuclear confrontation.
The concept of extended deterrence faces new hurdles in the face of Russian nuclear threats. On September 26, 2024, Russian President Vladimir Putin warned the West that Moscow would consider any conventional missile attack on Russia, if aided by a nuclear state, as an act of joint aggression meriting a nuclear response.
This strict Russian stance reflects Moscow’s fear that Western countries might use Ukraine to target Russian nuclear military and civilian sites. This concern is not unfounded, as Ukraine has previously targeted the Zaporizhzhia reactor after it fell under Russian control and reportedly attempted to target the Kursk nuclear reactor on August 17, 2024, according to Moscow’s claims which Ukraine has denied.
2. Targeting Civilian Reactors
Targeting nuclear reactors represents a potential deterrence measure that gained attention following the Russia-Ukraine conflict. Ballistic missiles, particularly hypersonic types, could potentially penetrate heavily fortified structures like nuclear reactors, causing catastrophic nuclear fallout if the containment structures were breached. Such a scenario would require multiple precision strikes and a substantial missile inventory and is especially effective where reactors are situated near strategic centres or where a nuclear incident could contaminate large portions of a small nation.
This strategy could serve as a form of conventional deterrence against a nuclear-armed adversary, provided the state has access to precision-guided ballistic missiles in sufficient numbers. In a high-stakes confrontation, threatening a nuclear adversary’s reactors could impose a form of deterrence by raising the stakes of escalation, though it remains a high-risk approach given the potentially devastating environmental and civilian impacts of such an action.
3. Nuclear Hedging
This strategy is defined as a “national approach to maintain, or at least appear to maintain, a feasible option to acquire nuclear weapons relatively quickly based on domestic technological capacity, within a relatively short timeframe spanning weeks to a few years.” Japan is often classified as a state adopting this approach.
However, having an advanced nuclear infrastructure capable of producing a full fuel cycle, while indicative of nuclear latency, does not necessarily mean a country seeks nuclear weapons. What characterises a hedging strategy is the combination of concerted efforts to achieve nuclear latency alongside evidence that a state is actively considering nuclear armament. In simple terms, nuclear hedging can be seen as possessing nuclear latency with an intent to eventually acquire nuclear weapons.
The United States withdrew its nuclear arms from South Korea in 1991 as part of efforts to persuade North Korea to open its nuclear facilities for IAEA inspection. When US efforts to halt North Korea’s nuclear program failed, and with North Korea developing nuclear capabilities that could potentially target American cities, South Korea requested the redeployment of US tactical nuclear weapons in October 2017. Additionally, calls within South Korea for nuclear armament grew stronger, with a Gallup poll showing 60% of South Koreans favouring nuclear capabilities for their country.
A notable difference of opinion exists between Washington and Seoul regarding the US’s role in the nuclear balance between the Koreas. South Korea prefers explicit assurances that the US would use nuclear weapons against North Korea if it initiated a nuclear attack. In contrast, Washington opts for ambiguous statements, promising a “swift, overwhelming, and decisive response” that would “end the Kim regime.” The US further states that its extended deterrence strategy leverages the “full range of American defensive capabilities, including nuclear, conventional, missile defence, and advanced non-nuclear capabilities.” Many South Koreans view this as an unclear indication of what the US response would actually entail, suggesting that even if North Korea uses nuclear weapons, the US might opt for a conventional response, heightening concerns in South Korea.
Consequently, nuclear hedging may be South Korea’s optimal choice, particularly as some experts argue the country possesses advanced nuclear technological capabilities. Its civil nuclear program is among the largest and most sophisticated worldwide, providing a robust foundation for potential military applications. This technological advancement implies that, if politically necessary, the shift from civilian to military nuclear capabilities could occur relatively quickly.
Some experts believe that Saudi Arabia might also pursue a nuclear hedging strategy should Iran continue progressing towards a nuclear weapon. Others argue that Saudi Arabia may instead seek to acquire nuclear arms from Pakistan as a countermeasure against a nuclear-armed Iran. These experts contend that the US could dissuade Riyadh from pursuing nuclear arms by providing security assurances in light of a potential Iranian nuclear threat.
4. Acquiring a Matching Weapon
Countries sometimes opt to develop nuclear weapons to counter their adversaries, as seen in the cases of the US and the Soviet Union, or India and Pakistan.
Saudi Arabia has repeatedly threatened to acquire nuclear weapons if Iran does, with the most recent statement on 20 September 2023. In an interview with Fox News, Crown Prince Mohammed bin Salman indicated that his country would be “forced” to obtain a nuclear weapon should Iran develop one. Senior government officials have previously expressed intentions to achieve full autonomy by developing a complete nuclear fuel cycle, including enrichment and reprocessing. Although Saudi Arabia might face challenges in obtaining the required nuclear technology and fuel from the US, China appears more willing to collaborate with Saudi Arabia on nuclear-related matters, including uranium enrichment within the limits permitted by the IAEA.
These strategies are not entirely independent. For example, South Korea’s threat to develop nuclear weapons in response to North Korean threats may be intended to pressure the US into offering a more explicit nuclear umbrella to protect Seoul against Pyongyang. In conclusion, countries adopt varying strategies to counter the risks posed by nuclear-armed adversaries. These approaches differ depending on the resources and constraints each state faces, as well as the extent of its nuclear program and its capacity to leverage these advancements for nuclear armament.
» By: Dr. Shadi Abdelwahab
(Associate Professor, National Defence College)
