5 Challenges for the South Korea-US Alliance

The United States and South Korea marked the 70th anniversary of their alliance with South Korean President Yoon Suk-yeol’s state visit to Washington, D.C. in late April After seven decades, the alliance has become an enduring partnership that continues to provide peace and security on the Korean Peninsula, while the relationship between the United States and South Korea has deepened to include close diplomatic, economic, technological, and cultural ties. 

Despite the long-standing nature of the alliance, the next decade may present the South Korea-U.S. relationship with more profound changes than any prior decade. These changes will come not only from shifts in geopolitics and North Korea’s weapons developments but also from climate change, technology and demographics. How the United States and South Korea respond to these five changes and the policy challenges that will develop from them will shape the prospects for bilateral relations.

In the most recent U.S. National Security Strategy, President Joe Biden described the coming decade as a “decisive decade” for the geostrategic competition taking shape with China. While this competition is often described in terms of a new Cold War, this geostrategic rivalry will play out differently for the United States and its allies. 

In contrast to the original Cold War, in which the allies and partners of the United States and the Soviet Union were largely in separate economic camps, China is integrated into the global economy and is the largest trading partner for more than 120 countries – including South Korea. China has also replaced the United States as the world’s largest manufacturing hub. These deep economic ties make states, including South Korea, more sensitive to their economic and diplomatic interests in China, a dynamic that was less of a factor during the Cold War. 

Since the United States continues to maintain a technological edge over China, it has turned to export controls to preserve its advantage while using subsidies to rebuild its manufacturing base. In the areas of semiconductors and electric vehicles, this has created tensions within the South Korea-U.S. alliance. South Korean firms are heavily invested in the production of semiconductors in China, and U.S. export controls and the CHIPS Act have raised concerns about the viability of maintaining those operations. The discriminatory granting of subsidies for electric vehicles – where U.S. national security policy and climate policy intersect – in the Inflation Reduction Act has also been a point of contention. 

With the expectation that the United States will continue to deploy export controls in areas related to cloud computing, quantum computing, biotechnology and artificial intelligence (AI), the China-U.S. rivalry is likely to continue to shape the economic relationship between the United States and South Korea. 

Geostrategic rivalry is also shaping policy regarding North Korea as it draws closer to Russia and China. For much of the last three decades, China and Russia have been partners, if not always as helpful as Washington would have hoped, in efforts to denuclearize North Korea. That is changing. 

With North Korea resuming its missile tests, China and Russia have provided political cover by blocking new resolutions and sanctions at the United Nations. North Korea has reciprocated Russia’s support by blaming the United States for Russia’s invasion of Ukraine, voting against U.N. resolutions condemning Russia’s invasion, and criticizing the transfer of U.S. tanks to Ukraine. At the same time, North Korea is reported to be providing Russia with ammunition, something Moscow hopes to continue, as Pyongyang seeks to negotiate an arms-for-food deal to deepen ties with Russia.

The South Korea-U.S. alliance faces the prospect of diminishing leverage in its denuclearization efforts as North Korea continues to develop its weapons systems while receiving political cover and likely economic support from Moscow and Beijing despite U.N. sanctions. While deeper ties among the three countries, driven by shifting geopolitics, do not eliminate the prospect of talks with North Korea, they significantly dim them. They also complicate South Korea’s ability to work with the United States in its geostrategic competition with China due to Seoul’s concerns related to growing Chinese influence over North Korea. 

Geostrategic and security concerns are not the only challenges the South Korea-U.S. partnership will need to address. If the next decade will be key for the geostrategic competition between the United States and China, a new U.N. report suggests that it will also be critical for averting the global temperature rises that would bring about extreme changes to the climate. 

The United States and South Korea have increased cooperation on climate change in recent years, but the cooperation will need to deepen and expand to other countries if there is to be measurable progress on quickening emissions reductions. The two allies will also need to avoid the types of disputes that have taken place over industrial policy in the Inflation Reduction Act. 

Climate change will also impact security policy for the alliance. North Korea’s already fragile infrastructure and agriculture will face greater strains from extreme weather. Those strains on food production could result in increased instability if they push the availability of food to more extreme levels than have been seen during the pandemic. 

The United States and South Korea are also undergoing demographic shifts with implications for national security. These shifts will be slow moving and play out over the next two decades but will be most dramatically felt in South Korea. Decades of declining births have resulted in decreases in both the working-age population and the overall population. These trends are unlikely to change anytime soon and have become more extreme in recent years. Since 2018, South Korea’s total fertility rate has fallen below 1.0, well below the population replacement rate of 2.1, and reached a new low of 0.78 in 2022. 

The demographic trends in South Korea have implications for the alliance. As the workforce declines and the population ages, South Korea will face declining economic growth prospects and increased strain on resources from rising healthcare and pension costs, but it will also face a declining number of conscripts for the military. Since 2018, South Korea has reduced its active-duty military from 618,000 troops to around 500,000. The current plan calls for maintaining those levels through 2027, but demographic trends will increasingly create pressures to reduce the size of active-duty forces further. Enlisted members currently account for 299,000 active-duty troops, but over the last two decades, male births have fallen from roughly 110,000 in 2000 to a little under 105,000 last year. As males born over the last two decades begin their service over the two decades ahead, there will be a shortage of roughly 80,000 enlisted members.

Technology will serve as one potential solution for South Korea’s troop shortages. Seoul is already experimenting with using AI to power drones for reconnaissance and image recognition, and is working to develop other strategies for the future use of AI in defense. Ultimately, AI could help with tasks related to the autonomous transfer of weapons, field medical diagnosis and treatment, and improved missile defense.

While AI may be able to help South Korea address the needs of future troop decreases, technology will also present challenges beyond the questions on the ethics of utilizing autonomous weapons and AI integration between U.S. and Korean systems. 

In contrast to the Cold War, when states largely monopolized strategic technologies, the private sector will play the dominant role in the development and deployment of AI, and there will be relatively low barriers to entry. Two of the more recent entries, ChatGPT and DALL-E 2, have shown the potential of AI, but also the possibilities for AI to be used as a tool of political subversion both domestically and by foreign powers; it is increasingly hard to know if text, sound, and images are real or artificial. 

Of all of the changes over the next decade, AI has the potential to be both the most profound for society, politics, economics, and national security, but also the one whose impact is most difficult to predict.

The next decade will look very different from the past decade, and will shape the decades to follow. To address these trends the United States and South Korean need to engage in deeper, long-term discussions about the future U.S. force posture on the Korean Peninsula to better prepare for the demographic shifts to come. There will also need to be more coordination between the United States and South Korea, and their partners and allies, on climate change and emerging technologies. 

Climate, demographic, and technological shifts will also take place against the backdrop of a different geostrategic context that is reshaping the threat from North Korea. Managing these disparate but interconnecting challenges will require deeper coordination between the United States and South Korea, but also an approach that integrates what used to be thought of as separate issues.