Key Takeaways: 

- Trump is dealing with a different kind of progressive South Korean government in his second term. 

- Ambition could backfire. The leaders should focus on reaffirming long-standing alliance principles rather than details on thorny security and defense issues. 

- Strategic flexibility, burden sharing and details on modernizing the alliance should be dealt with between working-level officials in both governments.

United States President Donald Trump and South Korean President Lee Jae-myung will meet for the first time on August 25 in Washington, DC. Trump and his first administration have worked with a progressive South Korean government before. However, it is not inevitable that the alliance is in for another bumpy ride simply because there is another progressive ally in Seoul. The new South Korean President Lee Jae-myung represents a departure from the traditional progressivism of his predecessors Moon Jae-in (2017-2022) or even Roh Moo-hyun (2003-2008). In other words, Lee may not possess deep, ideological convictions when it comes to dealing with Japan and the United States, although his critics claim he is “pro-China” for comments made in the past and “pro-North Korea” for allegedly transferring funds illegally to the regime when he was a provincial governor.

In fact, those around Lee claim that he is a foreign policy novice. Some who have worked closely with him even say “he does not care about foreign affairs,” meaning that his priority is domestic policy and domestic politics. Lee is also a self-proclaimed pragmatist, which will certainly be tested in his meeting with Trump and throughout his presidency.

The most notable difference from the Moon government is that half of the political appointees on Lee’s national security team are seen as pragmatic and half are considered ideological or traditional progressives. He has appointed pragmatic, career diplomats to lead the country’s national security and foreign policy. If Lee delegates foreign policy to them and accepts their recommendations, then South Korea’s foreign policy will exhibit more consistency than divergence with a conservative approach. This means that, unlike during the Moon government, the US-Korea alliance relationship will likely be quite smooth. However, Trump’s unpredictable style could tip the balance.

The first indication of such consistency is Lee stating before and after his election that his foreign policy will be based on the alliance with the US and trilateral cooperation with Japan. The architect of such approach is evidently National Security Advisor Wi Sung-lac who is respected by the foreign policy community in Seoul. He is known for his pragmatic, strategic mind and could have easily led foreign policy in a conservative administration. Wi has a strong ally on the team with newly-appointed Foreign Minister Cho Hyun. Their main challenge will be grabbing the ear of their president fully as Lee’s national security team also has ideological officials leading the country’s spy agency and Unification Ministry as well as traditionally-progressive mentors who could be influential without assuming an official role.

These three ingredients, if utilized properly, could portend a smooth working relationship with the United States and present more opportunities—perhaps even historical ones—than challenges for the alliance during Trump’s term and for Seoul’s own foreign policy. Washington, meanwhile, may not currently have a Senate-confirmed senior official with the kind of gravitas South Koreans would like to lead America’s Korea policy. But the State Department and Defense Department have strong working-level officials who understand alliance issues and the stakes that are involved in managing thorny factors in them.

US Strategic Flexibility and Alliance Modernization

While the summit date was suddenly set when Washington and Seoul struck a deal on Trump’s tariffs, the months leading up to it were shrouded with suspense and concern in Seoul. South Koreans will zero in on if and how the two leaders use the terms “(US military) strategic flexibility” and “alliance modernization,” which are being pushed by Trump’s administration. At a minimum, Trump will likely want to receive a financial pledge that Seoul will contribute more towards hosting US troops.

Lee will likely seek to focus their conversation on increasing South Korean military expenditures and avoiding a conversation about strategic flexibility, which entails the possibility of redeploying US troops stationed in South Korea flexibly to other conflict zones (i.e., Taiwan Strait). In fact, both leaders should allow their teams at the working level to hash out details on strategic flexibility and how to modernize the alliance with Seoul assuming more responsibility for deterring North Korea.

Trump’s comments about allies and “free riding” since his first presidential term have long primed South Koreans to expect him to demand more military expenditures for Washington’s defense commitment to South Korea. They saw Trump elicit pledges from NATO allies to raise defense spending to five percent of their gross domestic product (GDP). Seoul currently spends about 2.8 percent of GDP. Seoul appears willing to increase up to approximately 3.5 percent while potentially making additional contributions in kind, amounting to a total increase of about 1.5 percent.

Instead, South Korean concern has been driven by Trump’s nonchalant comments about wanting to withdraw US military forces from South Korea due to costs and comments made by Under Secretary of Defense Elbridge Colby before and after his confirmation. Colby believes that US troops based in South Korea should now be focused primarily on deterring China, rather than North Korea because Washington sees Beijing as a “pacing threat.”

The Trump administration is also seeking to modernize the alliance so that Seoul would focus more on deterring North Korea—which includes increasing expenditures on national defense capabilities for deterrence—while Washington focuses more on China in peacetime. In other words, Seoul would be sharing more of Washington’s security burden (known as “burden sharing”), which would include Seoul spending more to strengthen its own capabilities. Burden sharing is different from a cost-sharing agreement called the Special Forces Measures Agreement (SMA), which has long been a challenging negotiation to increase South Korea’s share of the costs to host USFK mainly due to Seoul’s need to receive National Assembly approval. The allies have made a prudent decision to negotiate burden sharing separately from SMA negotiations.

Colby has also been known to want explicit support for strategic flexibility and South Korea’s military involvement in a potential conflict. Seoul is firmly opposed to these two scenarios, let alone allowing them to be discussed between the two presidents.

US rationale behind seeking alliance modernization and strategic flexibility is that US Forces Korea (USFK) and the alliance need to contribute to America’s central security challenge too (i.e., China), just as USFK has been focusing on South Korea’s existential threat of North Korea. It is particularly difficult to argue otherwise when South Korea’s military capabilities are the strongest they have ever been since the 1950 Korean War (although its military readiness is a separate matter). After all, the two countries have a Mutual Defense Treaty (1953) and not a unilateral one. The Treaty, which provides the legal and fundamental framework for US troops stationed in South Korea, does not specify North Korea as the “potential aggressor” nor does it specify any aggressor against which the allies must deter armed attack.” This means that the mission of USFK is not limited to deterring and defending US allies against only North Korea in the Pacific.

The US National Defense Strategy is expected to be complete in late August or September with a Global Posture Review to follow it. Due to the “pacing threat” of China, America’s global military posture is expected to focus more on its navy and air force rather than its army. This means that the number of American troops stationed in South Korea could naturally decrease with, e.g., the deployment of modern weapon systems like fifth generation fighter jets, which require less “manpower” to operate them.

In this context, military capability is certainly more important than the number of American soldiers in Korea. Still, Seoul should seek to sustain a sufficient number of US troops that can deter and immediately fight Pyongyang. US troops are protecting both South Koreans and a large American expat community living there.

For Washington, strategic flexibility today means that USFK’s posture during peacetime will continue to be to deter North Korea while designating a small portion of it to maintain a deterrence posture against China during peacetime. It also means that during wartime, a portion of USFK could be deployed as necessary to a conflict zone. South Koreans fear this scenario would leave a security vacuum on the Korean Peninsula and hand North Korea an opportunity to provoke or even invade the South again.

The concept of strategic flexibility is not a new one. In 2003, Washington first broached the topic with Seoul and, after almost a year of negotiations, the term appeared officially in a 2006 Joint Statement between Secretary of State Condoleezza Rice and Foreign Minister Ban Ki-moon. Such discussions came against the backdrop of the September 2001 terrorist attacks on the US and the Iraq War, which led to Washington reorienting its global military posture to deal with its top security threat at the time. As a result, the Bush administration’s Global Posture Review led to a reduction of USFK from its previous 37,000 troops and redeployment to the Middle East.

Rice and Ban confirmed strategic flexibility to mean that “The ROK, as an ally, fully understands the rationale for the transformation of the US global military strategy, and respects the necessity for strategic flexibility of the US forces in the ROK. In the implementation of strategic flexibility, the US respects the ROK position that it shall not be involved in a regional conflict in Northeast Asia against the will of the Korean people.”

South Koreans were certainly anxious about the troop reduction. However, Washington’s decision and President Roh’s agreement to send Korean troops to Iraq were less controversial than today with China. Korean soldiers deployed to Iraq were also medics and combat troops for security and reconstruction missions in non-combat zones.

Metrics for Success

A successful summit would focus less on details regarding security, defense and trade issues. Instead, the two presidents should reaffirm long-standing alliance principles. Seoul should refrain from presenting Trump with a long, detailed list of asks and discussion topics because their efforts could backfire. Instead, it should deal with sensitive issues and specific demands at the working level of the US government.

Lee could express gratitude for US involvement in the Korean War and commitment to defending South Korea against regional threats. He could remind Trump of the importance of USFK’s role in deterring and potentially engaging North Korea militarily because a Taiwan contingency could expand into a simultaneous conflict on the Korean Peninsula that puts American expats’ lives at risk. Lee could seek reaffirmation of the US defense commitment to South Korea while pledging to spend more on military expenditures and the procurement of advanced weapon systems. He could also stress that Seoul should be consulted before Washington strikes any future deals with Pyongyang, and that any agreement should be advantageous to Seoul and the alliance’s interests.

Trump, meanwhile, has a propensity to go off script, but he should still avoid trying to secure an explicit agreement about US strategic flexibility and South Korean role in a potential Taiwan or South China Sea contingency. Their Joint Statement does not necessarily need to mention “strategic flexibility,” but if it must, then it would be sufficient to retain the same language used in 2006. After all, both US strategic flexibility and South Korea’s direct or indirect involvement are inevitable. If Trump gives Lee a hard time, Lee’s foreign policy professionals risk losing face, potentially resulting in an altered foreign policy approach from Seoul’s current trajectory.

Trump and Lee could reaffirm their country’s commitment to the alliance amid shifting security dynamics and agree to modernize it in broad terms to meet the needs of today and the future. They could also reaffirm that diplomatic engagement with North Korea is the desired approach while reaffirming the importance of deterrence and North Korea’s denuclearization.

The two leaders should also wait to discuss details of their framework agreement on trade issues until after their teams have sufficiently worked through the necessary measures to implement it.

Finally, another marker of success would be if the two presidents agree to continue implementing their countrys' 2023 Summit Joint Statement on deepening and expanding the alliance across all domains; the 2023 Washington Declaration on US extended deterrence and South Korean nuclear-weapons abstinence; and the 2023 Camp David trilateral summit agreements on expanding trilateral cooperation.

Ambition could backfire. The alliance would benefit from an amicable and respectful summit that focuses on key principles, especially when it will be the first meeting between two unpredictable leaders.