South Korea’s new President Lee Jae Myung will visit his US counterpart Donald Trump in Washington on August 25. Their meeting occurs at perhaps the most precarious period in the 72-year history of the alliance between the Republic of Korea (ROK) and the United States. The Democratic People’s Republic of Korea (DPRK) has continued to develop its military power and forged an exceptionally close partnership with the Russian Federation to the detriment of European as well as Asian security. The Moscow-Beijing relationship also remains stronger than ever, while North Korea’s ties with the People’s Republic of China (PRC) have substantially improved in the past year. The alignment between North Korea, China, and Russia, along with other new regional complexities, raises the risk of miscalculation and deterrence failure. Lee and Trump face such critical security questions as how to address DPRK’s military threats, Chinese and Russian hostilities, rebalancing defense commitments, and sustaining trilateral security cooperation with Japan.

The alignment between North Korea, China, and Russia, along with other new regional complexities, raises the risk of miscalculation and deterrence failure

Dealing with Pyongyang

Criticism of the traditional ROK-US strategy of relying on diplomacy, deterrence, and sanctionshas increased due to this strategy’s failure to prevent North Korean threats. The DPRK government has dismissed recent ROK and US diplomatic entreaties, deployed additional nuclear weapons, and provided unprecedented military assistance to the Russian invasion of Ukraine.

Faced with these setbacks, some analysts have called for scaling back ROK and US objectives. They want to concentrate for now on limiting North Korea’s nuclear arsenal rather than eliminating it. This arms control-focused approach would seek to reduce or freeze the core components of the DPRK’s nuclear weapons complex (nuclear warheads, delivery systems, fissile material, nuclear-related tests). The near-term priorities would become preventing North Korea from selling these components to other state or non-state actors, developing transparency and confidence-building measures, restoring regular dialogue channels, and alleviating North Koreans’ humanitarian problems.

Proponents believe these steps could contribute to building trust and advancing long-term disarmament; opponents worry that they would legitimize the DPRK’s status as a nuclear weapon state for an indefinite period.

Reducing Russian and Chinese Obstacles

Given the strong support that Moscow and Beijing provide to North Korea, particularly their refusal to enforce international sanctions, the earlier debate over whether “maximum pressure” could compel Pyongyang to make concessions, or whether sanctions relief and incentives should be offered in return for cooperation, has become meaningless. Since the DPRK can acquire copious volumes of fuel from Russia, food from China, and other previously restricted imports, South Korea and the United States can neither escalate economic pressure on the North sufficiently to compel concessions nor induce cooperation by offering to relax their own sanctions.

Though the Trump administration could apply secondary sanctions against Russian and Chinese companies that engage in commercial transactions with the DPRK, these firms, supported by their governments, have regularly circumvented international sanctions. If Seoul and Washington sought to bargain for their support, Beijing and Moscow would likely demand major concessions on other issues. There is also no guarantee that Russian and Chinese enforcement would improve since both governments have already violated the mandatory UN Security Council sanctions that they earlier voted to adopt. Furthermore, Russian firms are already so heavily punished that threats of additional sanctions would not present much of a deterrent, while the PRC could credibly threaten economic countermeasures against the United States and South Korea, such as by curtailing their critical mineral imports.

Divergent Diplomacy

The United States and South Korea could attempt to circumvent Russia and China through bilateral diplomacy with the North. To decrease intra-Korean tensions, the Lee administration has dismantled loudspeakers broadcasting anti-regime propaganda to the North, reduced the size of this month’s Ulchi Freedom Shield military exercise with the United States, and proposed reviving cooperative projects with the North. Setting aside demands that the North commit to denuclearization as a precondition for negotiations, Lee has outlined a three-stage plan with the goals evolving from freezing, then decreasing, then eliminating the North’s missile and nuclear programs.

Though Lee has pledged to coordinate intra-Korean policies with the United States, these outreach initiatives have evoked worries about diverging diplomatic priorities between Seoul and Washington. South Korean progressives, who are influential in Lee’s ruling Democratic Party, have traditionally sought to promote economic and humanitarian ties with North Korea while decreasing sanctions and border tensions. In contrast, Trump may want primarily to limit the North’s threats to the US homeland. Furthermore, Trump has been less critical of the Russian-DPRK military partnership than South Korean policymakers, who fear that with Moscow’s backing, Pyongyang will become more provocative.

In addition to the two governments’ possible diverging substantive priorities, they also likely favor different diplomatic styles. The Lee administration favors the traditional “action-for-action” approach in which South Korea and its partners would reward the North for incremental concessions. In contrast to this step-by-step approach, Trump has displayed a preference for “big bang” diplomacy in which the parties frontload concessions to drive rapidly toward a bold end state.

Though the North’s refusal to engage directly with Lee or Trump this far has averted a ROK-US diplomatic gap, tensions between Seoul and Washington would increase if either government perceived the other as neglecting its security priorities.

Burden Shifting

Trump wants to make US security alliances more economically beneficial to the United States and perceives even close security allies like South Korea as economic rivals. Though the ROK recently reached a new trade and investment deal with the United States, Trump will probably continue his efforts to induce Seoul to substantially increase its national defense spending and support payments for the United States Forces Korea (USFK). Through the Special Measures Agreement, the ROK government spends more than one billion dollars each year, mostly on South Korean contractors, to cover expenses related to the USFK.

Though the ROK recently reached a new trade and investment deal with the United States, Trump will probably continue his efforts to induce Seoul to substantially increase its national defense spending and support payments for the United States Forces Korea (USFK)

The Lee administration seems prepared to raise ROK defense expenditures due to the deteriorating Northeast Asian security environment. The resulting capability boost should dampen past South Korean-American tensions regarding when and under what conditions the ROK would assume wartime Operational Control (OPCON) over the US-ROK Combined Forces Command. Though Lee emphasized achieving OPCON transfer during his presidential campaign and the transition would align with Trump’s desire for US allies to assume greater responsibility for their own defense, concerns persist that North Koreans and others would perceive a hasty OPCON transfer as US eagerness to decrease its ROK-related defense commitments.

Strategic Flexibility

The current Pentagon leadership prioritizes preparing for a possible war against China, especially regarding Taiwan, and judges US allies by their support for this mission. US planners want strategic flexibility to draw on US forces and bases throughout the Indo-Pacific, including in South Korea, for potential contingencies. They are considering means to make USFK capabilities better suited for off-Peninsula contingencies, how USFK bases and other stationary assets can support missions at a distance, and whether to redeploy troops from South Korea to other locations.

In recent years, South Koreans have perceived greater security concerns regarding China and the sea lanes around Taiwan, which are vital for South Korea’s maritime trade. Nonetheless, the ROK national security establishment wants to continue restricting USFK combat forces for missions on the Peninsula. They also typically eschew public discussions of South Korea’s possible military roles in a Taiwan contingency to avoid antagonizing China to the detriment of the ROK’s economic and security interest. The PRC is the ROK’s primary trade partner and has employed commercial coercion against countries whose governments pursue policies Beijing opposes.

Furthermore, many progressive South Koreans still seek Chinese help managing North Korea, while some conservative ROK analysts fear the Pentagon’s preoccupation with PRC-related contingencies will downgrade US military preparations against North Korea. Both groups fear ROK “entrapment” in a Sino-American tussle and PRC participation on Pyongyang’s behalf in another Korean War. North Korea’s deployment of nuclear missiles near its Chinese border also increases the risk that PRC policymakers could perceive US and ROK strikes against DPRK nuclear assets as threatening.  

Trilateral Tensions

South Korea, Japan, and the United States have substantially enhanced their security cooperation in recent years. At their August 2023 Camp David summit, the presidents of the three countries agreed to convene annual trilateral exercises, share more information about DPRK missile launches, and cooperate more on missile defense. Japan plays a pivotal role in this trilateral equation. The US forces and bases in Japan would provide critical reinforcements for ROK and USFK forces during a war in the Korean Peninsula. Tokyo can also amplify South Korean and American messaging through its robust global partnerships. Since his election, Lee has made more favorable comments regarding ties with Japan and is visiting Tokyo for senior-level meetings before flying to Washington.

Though South Korean and Japanese policymakers share concerns about changing US economic and security policies, the recent political transitions in all three countries have called into question their level of defense collaboration in the future. Some ROK progressives worry that the growing security ties among South Korea, Japan, and the United States impede inter-Korean cooperation by constraining the ROK’s flexibility and intensifying DPRK, PRC, and Russian security anxieties. The Japanese defense establishment is more inclined than ROK national security managers to perceive the areas around Japan, the Korean Peninsula, and China as a single military theater. Tokyo is also pushing South Korea and other US allies to make greater commitments to defend Taiwan against PRC military threats.

Though South Korean and Japanese policymakers share concerns about changing US economic and security policies, the recent political transitions in all three countries have called into question their future level of defense collaboration

Scenarios

Seoul and Washington have established the goal “to strengthen the US-ROK Alliance into a future-oriented, comprehensive strategic alliance, and to modernize the Alliance in a mutually beneficial manner in the face of an evolving regional security environment.” How the two presidents address the above issues will go far toward determining whether they will realize these objectives.

Lee’s election reduces the likelihood that South Korea will pursue an independent nuclear deterrent. His predecessor, Yoon Suk Yeol, ruminated about national nuclear capabilities and demanded more explicit US nuclear deterrence guarantees, which the Biden administration provided. Opinion surveys regularly show general support among South Korean respondents for various nuclear options, but for now, Lee advocates Peninsula-wide denuclearization and relying on US pledges to defend the ROK. The United States has traditionally extended nuclear deterrent guarantees to allies like South Korea as an essential nonproliferation tool. The first Trump administration continued this policy, and Trump has not changed this stance. Should he do so or should South Korean confidence in US security guarantees substantially decline, ROK interest in acquiring nuclear weapons could increase.

Security cooperation among South Korea, Japan, and the United States will likely decline given diverging priorities and different domestic imperatives in Seoul, Tokyo, and Washington. Yoon was an atypical ROK president willing to buck South Korean animosities toward Japan in the interest of deepening ties among the Northeast Asian democracies against China and its authoritarian partners. Meanwhile, the weak Japanese government led by Prime Minister Shigeru Ishiba has less capacity to make concessions to South Korea. Additionally, Trump, unlike Biden, has not made fostering South Korean-Japanese ties a presidential priority. Though US domestic polarization has not directly affected the ROK-US alliance or trilateral relations among South Korea, Japan, and the United States, the Trump administration’s economic nationalism could impede the pooling of South Korean, Japanese, and US defense industrial capabilities, such as in the areas of critical minerals or shipbuilding. If the United States curtails its conventional deployments in South Korea or makes excessive host-nation support demands, the prospects that the ROK will accommodate rather than balance China to secure Beijing’s support for restraining the DPRK will rise, further increasing security strains with Washington and Tokyo.

The weakening of the ROK-Japan-US alignment would remove a driver of DPRK-Russia-PRC cooperation. Beijing would have less incentive to align with Pyongyang and Moscow if PRC concerns about Western containment against China in Northeast Asia decline and Chinese leaders perceive opportunities to exploit fissures between Seoul, Tokyo, and Washington.