02.11.23 Review

Defending the South: The US must give Seoul stronger security guarantees to deter it from developing its own nuclear weapons

In an era marked by the increasing propensity of autocracies to use force to alter the world's political power balances, the once-reliable special security guarantees provided by the United States to some of its allies, including South Korea, have lost their former lustre. South Korea, in particular, finds itself grappling with this issue due to the inability of the US and the international community to rein in North Korea's nuclear program and its expanding military cooperation with Putin's Russia. Analysts from the RAND Corporation contend that if the US does not enhance the reliability of its security guarantees, possibly by deploying nuclear weapons in South Korea, the republic may embark on the development of its own nuclear program.

Not so long ago, the model of special US security relationships and Israel, Japan, Taiwan, and South Korea served as a model in discussions about security guarantees for Ukraine. However, in today's world, characterised by escalating geopolitical tensions, shifting global military-political balances, and the increasing polarisation of American domestic politics, doubts have begun to emerge about the effectiveness of these guarantees. This is especially pronounced in South Korea, where residents are increasingly concerned about the apparent failure of the United States and the world community as a whole to ensure the nuclear non-proliferation regime with respect to their northern neighbour.

In a special report devoted to this issue, RAND Corporation experts cite data from a recent survey, which revealed that 58% of South Korean citizens are unsure about whether they can rely on US military support in the event of a North Korean attack. As President Yoon Suk Yeol put it, Washington's security guarantees mean that 'the US will take care of everything if necessary, so South Korea should not have to worry, but it is difficult to fully convince the Korean people of this right now.' The situation calls for immediate 'measures to strengthen nuclear assurances for the Republic of Korea,' the RAND experts state.

The doubts surrounding American security guarantees are tied to their lack of specificity, the report's authors point out. These assurances are based on the concept of extended deterrence, which entails a commitment to respond to a wide range of potential nuclear and non-nuclear scenarios to protect allies and partners. The latest version of the ‘Nuclear Posture Review’, the official document that defines the long-term US nuclear weapons strategy, states that 'any North Korean nuclear attack against the United States or its allies and partners is unacceptable and will result in the end of that regime.' Additionally, South Korea hosts approximately 30,000 US military personnel, making it the third-largest overseas contingent of US forces.

Nevertheless, there is a lack of a more precise definition of the content of these guarantees, akin to the clear-cut obligations set forth in Article 5 of the NATO treaty. In today's climate, where authoritarian states are willing to take military risks to shift the political balance of power, this is becoming a serious concern. Notably, the US has not even mentioned the guarantees provided to Ukraine in light of its renunciation of nuclear status, as established in the Budapest Memorandum.

South Korea's concerns about the reliability of US assurances have been mounting for at least a decade. The RAND analysts underscore that, during this period, the international community has attempted to prevent Pyongyang from acquiring its own nuclear capabilities, to no avail. Lately, these concerns have become increasingly tangible, especially in light of North Korea's plans to develop intercontinental ballistic missiles. It appears that Washington is unable to thwart these plans, especially given that Russia and China are preventing the United Nations Security Council from taking action against North Korean nuclear production and testing programs. South Korea is also alarmed by the emerging military cooperation between Russia and North Korea, and the US withdrawal of troops from Afghanistan has been a separate shock to Seoul, according to the analysts at RAND.

The RAND Corporation analysts believe that, unless immediate action is taken to fortify security guarantees, public sentiment in South Korea will inevitably gravitate towards the need for its own nuclear weapons program. Recent opinion polls indicate that the majority of South Koreans support the development of their own nuclear capabilities. Such a development could deal a severe blow to the Treaty on the Non-Proliferation of Nuclear Weapons.

In April 2023, the Presidents of the United States and South Korea signed the Washington Declaration, which aimed to strengthen nuclear safeguards for South Korea. Among other things, the two countries agreed to establish a Nuclear Advisory Group to reinforce extended deterrence. However, RAND argues that these measures are insufficient. A more serious US assurance could be a set of measures to establish parity with the North Korean nuclear threat, along with efforts to freeze the DPRK's nuclear programme. For this purpose, the US could modernise or construct a new storage facility in South Korea and deploy a limited number of tactical nuclear weapons. Moreover, Washington could modernise, at Seoul's expense, about 100 tactical nuclear weapons that are currently subject to dismantlement and place them in its own storage facilities allowing for rapid deployment to South Korea if necessary.

In total, the US could potentially transfer around 180 nuclear warheads to South Korea within a few years, along with 8 to 12 B61 nuclear bombs. Additionally, the US could allocate a portion of its ballistic missile-armed submarines operating in the Pacific Ocean for the purpose of a potential strike against North Korea.

Further, the White House must address a series of critical questions that it has thus far evaded. For instance, Washington has yet to specify the measures its threat of 'regime destruction' in Pyongyang would include in the event of North Korea's use of nuclear weapons. Moreover, it is imperative to determine the measures to counter the development of North Korea's nuclear potential. The RAND report’s authors question whether Washington and Seoul should contemplate a military operation to curtail its growth before it becomes an insurmountable threat.

They believe that the pronounced revisionist trajectory of the regime in Pyongyang will inevitably lead to a conflict with Seoul and perhaps even with Washington. Acting swiftly, even at the risk of provoking retaliatory measures from Pyongyang, is therefore paramount. Failure to do so may result in the US having to contend with Kim's attempts to establish a new world order based on Juche ideology and underpinned by a substantial arsenal of nuclear weapons within a few short years.