Obstacles to US–South Korea Alliance Regional Contingency Planning and Considerations for US Policy

  • Published
  • By Maj Jessica Reneé Taylor, USAFR



Despite displays of closer US–South Korea threat perception alignment, indicators point to the Yoon administration likely maintaining a nuanced approach between the United States and China—specifically in regional security cooperation. This article provides background on why the US–South Korea alliance has so far abstained from regional contingency planning amid a growing China threat. In addition, the article argues that South Korea is unlikely to support the alliance cooperating on US-led regional contingency planning due to the continued enormous influence that Beijing bears on the trajectory of South Korea’s economy, the likely continued divide in Japan–South Korea relations, and the polarizing political environment within the South Korean and US governments. The article concludes with considerations for US policy toward the US–South Korea alliance.


In the waning months of South Korea’s 2022 presidential election, then-candidate Yoon Suk-yeol published a vision for his foreign policy agenda in Foreign Affairs, “South Korea Needs to Step Up: The Country’s Next President on His Foreign Policy Vision.”1 Throughout the piece, Yoon criticized the outgoing Moon Jae-in administration for not taking a principled stance in the US-China “great-power competition” while also calling for strengthening South Korea’s alliance with the United States. Yoon assessed that the Moon administration allowed South Korea’s alliance with the United States to deteriorate while instead prioritizing achieving inter-Korean reconciliation despite the evolving threat from North Korea. However, what was most striking about Yoon’s foreign policy vision was his criticism that South Korea had “failed to adapt” amid the intensifying US–China competition. To this end he called for South Korea to take the initiative in the broader region, to consider joining multilateral regional cooperation initiatives in phases, and to take part in trilateral security coordination with the United States and Japan.

During the US Trump and South Korean Moon administrations, the alliance remained divided toward constructing a unified approach to maintaining stability in the Indo-Pacific region. For South Korea’s part, the Moon administration’s strategy of ambiguity—whereas it avoided taking sides between Washington and Beijing amid their growing interstate tensions—was seen as a significant obstacle to the alliance’s ability to address the threat that China posed to the region’s stability. However, this strategy was out of line with the South Korean public’s sentiment as multiple public polls displayed a growing concern of the threat that China posed to South Korea and the region.2 And notably, in some polls the public even identified China rather than North Korea as the greatest state threat to South Korea.3 In addition, polling displayed support for strengthening South Korea’s alliance with the United States to serve as a bulwark to the growing threat China posed to South Korea.4 Thus, considering Yoon’s foreign policy vision and the South Korean public’s sentiment, observers speculated that with Yoon’s ascendance to the presidency the US–South Korea alliance would finally expand its formalized and routine contingency planning beyond the peninsula to regional threats. However, as the realities of the office have settled in, indicators have pointed to the Yoon administration instead refraining from joining US-led regional contingency preparedness.

The Necessity of US–South Korea Regional Contingency Planning

As of this writing North Korea has reaffirmed its stance as a nuclear-weapon state. In addition, Pyongyang declared that it will never seek to rid itself of nuclear weapons if nuclear weapons exist elsewhere.5 Shortly after these declarations, North Korea followed up with a series of missile launches, including its first launch over Japan since 2017.6 Pyongyang’s continued defiance of UN Security Council resolutions and destabilizing activities have led to increased South Korea, Japan, and US trilateral security cooperation aimed at the North Korean threat. Pointedly, this increase in cooperation comes as the Yoon administration has sought to improve relations with Japan. However, what remains to be seen is additional trilateral cooperation toward the growing threat China poses to regional stability.

While commentators debate whether China will seek to absorb Taiwan by force, President Joe Biden has gone so far as to unequivocally confirm that the United States will come to the aid of Taiwan in the event of a Chinese invasion.7 And as a specific indication that the Biden administration means to make good on its declared commitment to Taipei, the United States and Japan are making efforts to create formal contingency plans to respond to a Chinese invasion of Taiwan.8 Arguably, a growing US-led coalition dedicated to defending Taiwan amid growing cross-strait tensions will have implications for China’s nuclear employment doctrine. Washington is specifically concerned that Beijing may seek to change its “no first use policy” and or increase the alert status of China’s nuclear force.9 The growing concern about a Chinese invasion of Taiwan, coupled with the possibility of a shift in China’s nuclear employment doctrine, poses a variety of complications for the US–South Korea alliance’s force posture. For instance, a priority concern should be the alliance ensuring it is prepared for simultaneous contingencies across the Taiwan Strait and on the Korean Peninsula. This hypothetical situation could involve several simultaneous threats from the nuclear weapon states China, North Korea, and possibly even Russia. Russian president Vladimir Putin has alluded that the nuclear-use taboo that has held since 1945 is possibly not ironclad and that even great powers can threaten the use of nuclear weapons to hold annexed territory. However, recently, President Yoon avoided promising to commit that South Korea would move to join a US-led effort to come to Taiwan’s defense in the event of a Chinese invasion.10 As cross-strait tensions continue to mount and the Biden administration continues to reiterate its commitment to come to Taiwan, the question is whether the US–South Korea alliance will finally evolve to expand its military cooperation beyond the peninsula to regional contingency planning.

In the coming months, Seoul is expected to release its Indo-Pacific strategy, the first of its kind for a South Korean government.11 So far under the Yoon and Biden administrations, US–South Korea joint public statements have indeed included references to the alliance working together on regional stability issues. Of note are references to “supporting the stability of the Taiwan strait” and of “the South China Sea.” which have led to speculation that the US–South Korea alliance may seek to expand its to regional contingency planning.12 Adding to the speculation, the August 2022 Korea–United States Integrated Defense Dialogue joint statement reinforced “the importance of preserving peace and stability in the Taiwan Strait” and pledging “to continue promoting defense and security in the Indo-Pacific region.”13

However, indicators point to the Yoon administration likely maintaining a nuanced approach between the United States and China–specifically in regional security cooperation. As a point of clarification, due to the hallmarks of an alliance being the promise of retaliation on behalf of an ally, here the term alliance refers solely to the military cooperation between South Korea and the United States as formalized under the 1953 US–South Korea mutual defense treaty. As such, while South Korea and the United States have expanded their relationship to areas beyond military cooperation, so far coordination in these areas lacks the guarantee of retaliation beyond kinetic attacks to legally owned territory.14 Also, like the alliance’s cooperation on the North Korea threat, here contingency planning refers to the formalization of operational plans and their associated military exercises to ensure military preparedness for a possible contingency. In other words, debate as to whether South Korea will decide to join an ad hoc response to a regional conflict, such as its support of the United States in the Vietnam War or the Iraq War, is not within the realm of this article’s analysis.

Abstaining from Regional Security Cooperation: The US–South Korea Alliance Status Quo

As concerns of a US–China conflict have risen in the decades following the Cold War, the status quo for successive South Korean governments has been a focus on the North Korean threat while maintaining a balance in Seoul’s approach to relations with its sole security ally—the United States—and its now number-one trade partner: China. Amid the current rise in regional tensions, the current US Forces Korea commander, GEN Paul LaCamera, USA, has stressed the need to include South Korea in US-led regional contingency plans.15

Of importance surrounding the prospect of regional US–South Korea contingency planning the 1953 treaty emphasizes that the allies agree to work together to further regional stability. 16 Meanwhile, concerns surrounding the trajectory of the Indo-Pacific’s stability have become increasingly salient for South Korea. As its export-oriented economy is reliant on trade flow through the South and East China Seas it would be a natural evolution for the alliance to develop regional contingency response plans.17

President Biden’s continued declarations that the United States would come to the defense of Taiwan in response to a Chinese invasion intensifies the debate surrounding whether the alliance should include a focus on regional contingency planning.18 Notably, former US and South Korean alliance military leaders have highlighted the necessity for the alliance to consider how a Taiwan Strait armed conflict would impact the alliance. For instance, US Secretary of Defense Mark Esper specifically warned that South Korea is unlikely to be able to avoid being drawn into the conflict.19 And US–South Korea Combined Forces Command (CFC) deputy commander and the current Korea Association of Military Studies president, General Leem Ho-young, ROK Army, retired, went a step further, warning that the alliance should consider the possibility of simultaneous contingencies across the Taiwan Strait and on the Korean Peninsula.20

The pressure for the alliance to expand its contingency planning beyond the peninsula has been building for years. A crucial pivot for the alliance was when the George W. Bush administration decided that as the international threat environment continued to evolve the United States could no longer have troops stationed overseas dedicated to a sole purpose—such as the North Korea threat.21 To this end, the Bush and ROK Roh Moo-hyun administrations were able to reach a compromise on the US request to have the “strategic flexibility” to mobilize its forces from South Korea for contingencies external to the peninsula. However the Roh administration, out of concern South Korea would be drawn into a regional conflict, stipulated that the United States would first consult Seoul prior to the use of US Forces Korea personnel.22 Thus the alliance’s agreement of strategic flexibility for US Forces Korea along with South Korea’s implementation of a strategy of ambiguity has so far been the alliance’s approach to how the United States could respond to a regional conflict absent South Korean military forces’ involvement.23

But as tensions across the Taiwan Strait and on the peninsula have intensified, questions continue to mount as to whether the alliance would collaborate in the defense of Taiwan in response to a Chinese invasion. This conversation has been increasing in public discourse. For instance, while serving on the US Forces Korea staff during the Moon administration, this author participated in roundtable discussions around this question with alliance key stakeholders. The frequent refrain was that the alliance could not cooperate on regional threats because the Korean public traditionally does not support such collaboration external to the peninsula. In addition, despite the likely impact of cross-strait instability to South Korea’s security, some even argued that the responsibility for a regional contingency response should solely fall to the US Indo-Pacific Command absent US–South Korea CFC support.24 To this end, South Korean government officials have confirmed that, despite the simultaneous intensification of cross-strait and inter-Korean tensions, the alliance has yet to discuss implications of this scenario.25 However, in a significant departure from historic sentiment, late 2021 public polling displays that the South Korean public would actually advocate for South Korean military forces supporting a regional coalition coming to the defense of Taiwan in the event of a Chinese invasion.26

Russia’s invasion of its democratic neighbor, Ukraine, has likely heightened concerns of authoritarian states seeking to undermine the democratic freedoms and sovereignty of their neighbors. Notably, the South Korean public staunchly disapproved of President Yoon’s decision not to meet with US House Speaker Nancy Pelosi during her 2022 visit to Seoul. As her visit directly followed her trip to Taipei, which sparked ire from China, the public notably viewed Yoon’s actions as trying to appease China.27

However, the Yoon government is still unlikely to signal support in his administration’s Indo-Pacific strategy for the expansion of alliance to regional contingency cooperation. The remainder of this article will examine how South Korea’s economic security, South Korea–Japan tensions and the polarized political environments in South Korea and the United States, are not conducive to the Yoon government supporting alliance regional contingency planning. The article will conclude by providing considerations for US policy.

Obstacles to Supporting US-led Regional Security Cooperation

China’s Influence on the Trajectory of South Korea’s Economy

While the Korean public increasingly assesses China as a threat, the public’s actual number-one strategic concern is the state of South Korea’s economy.28 Complicating matters, South Korea has yet to attain its goal of diversifying its economy to have less reliance on China. Thus, any tensions with China, poses a risk of negatively impacting South Korea’s economy.

Consequently, as Beijing is sensitive to US-led efforts to challenge China, Seoul must be diligent in what areas of its foreign policy South Korea is willing to risk tensions with China. For instance, the Yoon government has displayed its willingness to push back against China with reference to the Yoon government’s desire to deploy more US Terminal High Altitude Area Defense (THAAD) anti-ballistic missile systems to South Korea.29 Yoon’s decision follows China’s retaliation on South Korea’s economy during the former Moon administration as a result of Seoul’s decision to deploy the US THAAD system on South Korean soil in the first place.30 However, for Yoon’s current stance, Seoul is able to point to the North Korean threat and, thus, emphasize that South Korea’s decision is not an effort to threaten China. On the contrary, Beijing would view Seoul joining US-led regional contingency planning as South Korea’s participation in military plans for a future armed conflict with China.

President Yoon is likely also concerned about his limited options to improve South Korea’s flailing economy in the near term. To this end, the Yoon administration currently is seeking to strengthen trade with China.31 Thus, considering Seoul’s concerns about the considerable impact China currently has on South Korea’s economic trajectory, the Yoon government is unlikely to risk joining US-led regional contingency plans.

Beijing has displayed that Seoul merely mentioning topics sensitive to China leads to China issuing heavy public rebukes and warnings to South Korea.32 Thus, absent successful efforts to lessen the impact of China’s influence on the trajectory of South Korea’s economy, Seoul will continue to avoid risking another round of Chinese economic retaliation.

As a result, China has devised an avenue to influence South Korea’s strategic decision making within the US–South Korea alliance without triggering US treaty security guarantees. China demonstrating its ability and willingness to weaponize its economy will pressure the Yoon government to abstain from joining US-led regional contingency plans. However, complicating matters is the fact that regional contingency planning would need to incorporate Japan amid continued South Korea–Japan tensions.

The Necessity of Bridging the South Korea–Japan Divide

Amid a regional contingency, the United States will seek support from its allies. For instance, the US–Japan alliance is devising contingency plans in the event the alliance needs to come to the defense of Taiwan. But complicating matters, bridging the divide in South Korea–Japan relations is a crucial component to successfully integrating South Korea into US-led regional contingency cooperation.

The recent deterioration of South Korea–Japan relations stems from a divide over the terms of their reconciliation in response to Japan’s manner of colonial era rule of Korea. Under the Moon and Abe administrations South Korea and Japan even struggled to collaborate on the traditional North Korean missile threat. While there has been an uptick on trilateral cooperation on the North Korean threat since the ascendance of the Yoon and Kishida administrations, trilateral cooperation on the regional China threat would truly be unprecedented.33

The continued impasse in South Korea–Japan relations prevents the interstate trust and public support necessary to cooperate toward regional contingency plans. Although there has been some decrease in tensions, hurdles remain to reconciling the South Korea–Japan relationship. For instance, the South Korean court ruling that still calls for the liquidation of South Korea–based Japanese business assets to compensate Korean victims of Japan’s colonial forced labor policies.34 Despite the continued delay in implementation of the ruling providing diplomatic space to find another solution, so far neither Seoul nor Tokyo have displayed a willingness to give any ground on the issue. The Yoon government is in a particular conundrum, as seeking to influence the South Korean courts would amount to executive overreach of an equal branch of government. Concurrently, Japan’s Kishida administration has warned that South Korea–Japan relations will deteriorate to a point of no return if the South Korean courts go forward with the liquidation ruling.35

Furthermore, Japan has not returned South Korea to its whitelist of trade partners and maintains key semiconductor industry–related materials on its export to Korea control list.36 While these moves were seen in Seoul as a retaliation to the court ruling, Tokyo has asserted that the measures were due to export security concerns in South Korea of technologically sensitive items. During the Moon and Abe administrations, some Japanese government commentary even voiced disapproval of South Korea joining the G7 out of reported concern that Seoul had different regional threat perceptions regarding China and North Korea than the bloc.37 Also complicating matters is the lack of expendable political capital of both the Yoon and Kishida governments. As of this writing, both governments are experiencing low approval ratings due to internal domestic strife.38 In concert with South Korea’s and Japan public’s low approval for each other, there is little room, if any, for either the Yoon or Kishida government to make any concessions.

However, observers speculate that the antagonism between the South Korean and Japanese publics may ease due to shared growing concerns about China. But absent reconciliation on South Korea–Japan historical issues, South Korea’s court order to liquidate Japanese businesses’ assets, and South Korea–Japan trade issues, obstacles will remain to any South Korean government having the political space to join US-led regional contingency planning. But even absent concerns surrounding South Korea–Japan tensions, the increasingly divisive political environments of the South Korea and US governments also represent a considerable barrier to US–South Korea alliance regional contingency planning.

Political Polarization within South Korea and the United States

To make the historic shift of expanding the US–South Korea alliance to collaboration on regional contingency planning, the Yoon government would need the support of South Korea’s major political parties and to have faith in the trajectory of the US government and its enduring dedication to the alliance. A review of these areas casts doubt on prospects for the Yoon administration moving to support South Korea’s inclusion in US-led regional contingency planning.

Political Division in South Korea

South Korea’s 2022 presidential election results illustrate the increasingly polarized nature of South Korea’s political environment. While Yoon won the election, he did so by the smallest margin in the history of South Korea’s democracy.39 The slim margin of victory means that President Yoon does not have an overwhelming political mandate to make drastic changes to South Korea’s foreign policy, especially at the risk of further jeopardizing the country’s economy.

The polarized environment will likely mean less cooperation between South Korea’s leading political factions—the ruling conservative People Power Party (PPP) and its opposition the Democratic Party. Since taking office, Yoon, like previous South Korea presidents, has launched investigations into the former opposition administration, likely further entrenching the political divide.40 Yet Yoon is in a particularly peculiar situation, as the opposition party maintains the majority of seats in the National Assembly, South Korea’s legislative branch.41 Furthermore, the former Democratic Moon administration aimed to avoid acknowledging the threat China poses to South Korea. Thus, as the composition of the Democratic Party majority National Assembly is overwhelmingly the same as it was under Moon, the legislature is unlikely to support and fund foreign policy objectives that depart from the party’s platform under the Moon administration. For instance, the Democratic Party’s staunch criticism of Yoon’s efforts to broker peace with Japan displays the opposition party’s willingness to thwart Yoon’s foreign policy agenda despite security concerns.42

In addition, any moves such as joining regional contingency planning that lead to economic consequences will be feverishly criticized and used toward defeating the PPP in the next presidential and legislative elections. Thus, the PPP will also look to strategically formulate policies that do not risk the party losing future elections. However, a similar political environment in the United States also poses a significant impediment to South Korea joining US-led regional contingency planning.

Political Division in the United States

The polarization within the US government has shown that the division could possibly thwart the Biden administration from furthering its foreign policy objectives. Despite the bipartisan consensus on the US needing to address the China threat, political divisiveness has threatened to stymie the US government’s efforts to address the China challenge. For example, US Senator Mitch McConnell (R-KY) threatened to withhold Republican support of the Creating Helpful Incentives to Produce Semiconductors and Science Act (CHIPS). As the name implies, the CHIPS contains provisions to address portions of the Biden administration’s Indo-Pacific Strategy objectives related to ensuring US access to the global semiconductor supply chain.43 Senator McConnell, the minority leader in the US Senate, threatened to withhold Republican support for the bill if the Democrats moved forward with an unrelated reconciliation bill package. In response, the Biden administration lamented that Senator McConnell was willing to “hold hostage” legislation designed to make the United States more competitive with China.44 The episode illustrates the inherent risk in allies joining US-led efforts. Senator McConnell’s threat to derail legislation on China should cause worry for US allies, especially South Korea. There are risks of allies supporting a plan that may threaten their strategic stability only for that initiative to possibly not obtain the necessary support in the US government to come to fruition in the first place. The specter of such a US legislative failure following displayed public support from the South Korean government for an initiative that might antagonize Beijing might well torpedo Seoul’s willingness to bear the wrath of China’s economic retaliation for South Korea’s strategic regional security alignment with the United States.

To complicate matters further, the political environment in the United States, could lead to the reelection of former president Donald Trump or another candidate that holds Trump’s confrontational views toward continued support of US alliances. While the US public has displayed continued support for the US–South Korea alliance, Trump’s questioning of the value of US alliances during the 2016 election was not enough to prevent voters from electing him.45 During the Trump administration, this author observered South Korean officials voicing their concern that Trump could one day, on a whim, end the alliance or make concessions with North Korea or China that were not within South Korea’s interests.46 Thus, the Yoon administration is likely watching the trajectory of the US political discourse to ascertain what are the different possibilities for the number of US 2024 presidential election contenders’ approaches to the future of the US–South Korea. As a result, the Yoon administration is likely seeking to hedge amid an uncertain future of the US government’s approach to the US–South Korea alliance.

It is reasonable for any South Korean government to be cautious against aligning with US-led efforts to deter and be prepared for Chinese regional armed aggression. Seoul is likely concerned US policies may not endure a change in administrations, or worse, a future US president could make the unfathomable decision to end the US alliance with South Korea. As a result, Seoul would be left to deal with China’s ire due to South Korea’s joining US-led regional contingency planning.

However due to proximity to China, a regional conflict with China is likely to impact US Northeast Asia allies irrespective of whether they supported US-led contingency planning. For example, simply due to the US military footprint in South Korea, China is likely to perceive South Korea as a threat amid a US–China kinetic conflict. To this end, Washington needs to consider how to better support its allies to enable for collective efforts toward regional security strategy.

Considerations for US Policy

Washington first needs to better consider Seoul’s unique position when it comes to seeking South Korea’s inclusion in US-led Indo-Pacific contingency planning efforts. Seoul’s foreign policy will need to take into consideration South Korea’s proximity to the nuclear armed states of China, Russia, and North Korea and the growing strategic collaboration among these three amid a global economic downturn. In addition, Seoul must consider that a continued fraught South Korea–Japan relationship, in tandem with concerns of possible future US abandonment, could lead to South Korea’s isolation in an increasingly dangerous neighborhood.

In terms of US abandonment, while serving on the US Forces Korea headquarters staff, this author noted concerns among South Korea’s alliance supporters and key stakeholders that Washington may seek to eventually end its alliance with South Korea in a manner similar to the Carter administration’s 1979 decision to terminate its alliance with Taiwan.47 Carter’s decision to end the US–Taiwan alliance at China’s behest is significant for the administration having done so without offering any security guarantee for Taiwan.48 Regional observers usually proclaim that allies fear the United States may have what is often referred to another “Nixon moment” that rattled regional allies when Washington first moved to open ties with then previous foe Beijing in the early 1970s.49 However, it is also fair to argue allies would be concerned that a US administration could have a “Carter moment,” and possibly move to end an alliance with say South Korea to broker peace with Beijing,. Thus, the United States needs to continue to reiterate its enduring support to the defense of South Korea while noting some of the damage done by previous administrations.

Furthermore, as the United States is South Korea’s sole ally and was previously its number-one trading partner, the alliance historically had less concerns about external influences on the alliance’s combined decision making. But when China surpassed the United States to become South Korea’s number-one trading partner in 2004, the alliance should have considered how this shift would impact alliance coordination.50 Thus, the United States needs to develop a more holistic approach to strengthening and expanding the US–South Korea alliance to meet South Korea’s evolving regional threat environment more concretely. To better enable South Korea to participate in an expansion of the alliance, Washington should seek to evolve US security guarantees to Seoul. For instance, China’s economic retaliation against South Korea’s economy amid Seoul’s THAAD deployment decision failed to elicit any response or retaliation from Washington. As a result, discourse among the South Korean public called for the exercise of caution surrounding Seoul’s strategic decision making within the alliance out of fear of further Chinese economic retaliation.51

Beijing’s economic retaliation is particularly troublesome as China skillfully does not explicitly link any economic retaliation to a state’s action viewed as harmful to Chinese interests. For instance, Beijing never portrayed its retaliation against South Korea’s economy following the THAAD deployment decision as tied to that particular issue.52 China’s economic attacks on its trade partners have so far been related to supposed unrelated concerns. This informal retaliation may render efforts toward US–South Korea economic retaliation collaboration that much more difficult. In the meantime, the concerns of further economic retaliation amid a global economic downturn will likely cause the Yoon administration, South Korea businesses, and the South Korean public writ large to be wary of supporting alliance decisions that could spark China’s ire.

Furthermore, Washington should consider avenues for adding to Seoul’s political space for making innovative decisions that aid in strengthening and evolving the alliance. For instance, as of this writing, the provisions of the Biden administration’s Inflation Reduction Act (IRA) have incited significant uproar in South Korea.53 The IRA provides tax breaks to electric vehicle (EV) companies that manufacture their vehicles in North America.54 In response the South Korean public has expressed outrage, as most South Korea companies manufacture their EVs in South Korea prior to exporting them to the US.55 South Korean companies have voiced concern they will lose out, as their vehicles may end up being more expensive than EVs manufactured in North America. Thus, in South Korea the IRA provisions are viewed as yet another protectionist agenda akin to those espoused by previous US administrations aimed at increasing the economic prosperity of the US economy with little regard for the impact to allies.

The uproar comes amid Seoul’s limited near-term options to diversify the South Korean economy to have less reliance on China and as several of the country’s companies have pledged increased investment in the United States. This increased investment in the United States, through projects such as Samsung’s upcoming semiconductor fabrication facility, are expected to provide significant benefits to the US economy.56 However, public discourse illustrates that South Koreans are questioning the benefit of this increased cooperation with the United States.57 Debate has even included questions as to whether Korean businesses should go forward with their investments and if Seoul should continue to negotiate its joining of US-led initiatives, like the semiconductor alliance, that risk China’s ire. Thus, some of Washington’s policy decisions, such as exclusionary IRA tax breaks, risk limiting the political space in which Seoul must make risky decisions such as supporting the expansion of alliance cooperation to regional contingency planning.

In addition, while Washington seeks to further US–South Korea–Japan trilateral security cooperation, it should consider the US approach toward aiding the resolution of South Korea–Japan tensions. First, Washington should move to remain neutral in the South Korea–Japan divide, while also privately considering the unique concerns on both sides of the conflict. For instance, South Korea disapproved of the Trump administration publicly admonishing Seoul’s threats to terminate its intelligence-sharing agreement with Japan.58 It is understandable that Washington would want to ensure efforts toward trilateral intelligence sharing amid an increasing North Korean threat. However, it did not bode well for the US mediation position amid the continued deterioration of South Korea–Japan tensions when Washington did not also criticize Japan’s part in the deterioration of its relations with South Korea. For instance, Washington abstained from at least publicly criticizing Japan for its export controls on key semiconductor materials to South Korea, a move that has harmed industries in both South Korea and Japan.59

The US move was particularly concerning as South Korea was seeking limited avenues to motivate Tokyo to reverse Japan’s course on its trade retaliation on the Korean. Thus, Washington’s pressure for Seoul to shift its stance on the intelligence-sharing agreement absent the same criticism of Japan lessened the political capital of the Moon administration. Thus going forward, Washington should seek to enhance the political space Seoul has to bridge its divide with Tokyo while remaining neutral to maintain each public’s support and its ability to be an honest broker.

In conclusion, it is within Seoul’s vested interests for there to be a strong deterrent to Chinese regional aggression. While the Yoon government is so far vague on its position regarding participating in a US-led defense of Taiwan, the stability of Taiwan and the South and East China Seas is crucial to South Korea’s strategic stability. However, South Korea will likely continue to focus more narrowly on the existential threat North Korea poses to South Korea and China’s influence on South Korea’s economic trajectory. Therefore, absent an evolution in how Washington views and responds to threats to South Korea’s stability, the US–South Korea alliance will continue to struggle to adapt to threats to regional stability that emanate beyond the Korean Peninsula.

Maj Jessica Reneé Taylor, USAFR

Major Taylor is a logistics officer in the US Air Force Reserve (USAFR), a geopolitical strategist, and a PhD student in security studies at Princeton’s School of Public and International Affairs. Jessica has served in the Department of Defense in military and civilian capacities since 2005. Just prior to coming to Princeton, from 2019–2021, Jessica was serving as an Indo-Pacific geopolitical strategist on the headquarters staff of United Nations Command, Combined Forces Command and US Forces Korea. While at Princeton, she will focus on US Northeast Asia alliance cooperation.

1 Yoon Suk-yeol, “South Korea Needs to Step Up: The Country’s Next President on His Foreign Policy Vision,” Foreign Affairs, 8 February 2022,

2 Sea Young Kim and Sook Jong Lee, “South Korea Perception of the United States and China: United States, a more favorable Partner than China,” East Asia Institute, 21 July 2020,

3 Sangsin Lee et al., KINU Unification Survey 2021: US-China Conflict & South Korean Public Opinion (Seoul: Korea Institute for National Unification, 2021), 41,

4 Kim and Lee, “South Korea Perception of the United States and China.”

5 “Second-day Sitting of 7th Session of DPRK Held,” Rodong Sinmun, 9 September 2022,

6 Hyonhee Shin, Josh Smith and Kantaro Komiya, “North Korea conducts longest-range missile test yet over Japan,” Reuters, 3 October 2022,

7 President Joe Biden, interview with Scott Pelley, “Biden tells 60 Minutes U.S. troops would defend Taiwan, but White House says this is not official policy” 60 Minutes, 18 September 2022,

8 “Japan and U.S. draft operation plan for Taiwan contingency,” Japan Times, 23 December 2021,

9 Center for Strategic and International Studies, “How is China Modernizing its Nuclear Forces,” China Power, 28 October 2020,

10 Yoon Suk-yeol, President of South Korea, interview with Fareed Zakaria, “South Korean President: North Korea remains an imminent threat,” Global Public Square, 25 September 2022,

11 Andrew Yeo. “Can South Korea chart a path between the US and China in the Indo-Pacific,” Order from Chaos (blog), 15 August 2022,

12 “United-States Republic of Korea Leaders’ Joint Statement” (briefing, White House, 21 May 2022),

13 “Joint Press Statement for the 21st Korea-U.S. Integrated Defense Dialogue,” 17 August 2022,

14 Mutual Defense Treaty Between the United States and the Republic of Korea, 1 October 1953,

15 Gil Yun-hung, “USFK command nominee: S. Korea-US alliance can cooperate beyond Korean Peninsula,” Hankyoreh, 20 May 2021,

16 Mutual Defense Treaty Between the United States and the Republic of Korea.

17 Center for Strategic and International Studies, “How Much Trade Transits the South China Sea,China Power,

18 David Brunnstrom and Trevor Hunnicutt, “Biden says U.S. forces would defend Taiwan in the event of a Chinese invasion” Reuters, 19 September 2022,

19 Esther Chung, “Esper predicts Korean involvement in any Taiwan conflict,” Korea Joongan Daily, 13 July 2022,

20 “Agenda,” (Third Harvard Korean Security Summit: “Korea—A Catalyst of Global Trends, 19–21 July 2022),

21 Scott Snyder, ed., The US–South Korea Alliance: Meeting New Security Challenges (Boulder, CO: Lynne Rienner, 2012), 1.

22 Scott A. Snyder, South Korea at the Crossroads: Autonomy in an Era of Rival Powers (New York: Columbia University Press, 2018), 122.

23 Snyder, South Korea at the Crossroads, 139–40.

24 The author served as an Indo-Pacific geopolitical strategist on the Headquarters Staffs of United Nations Command, Combined Forces Command and US Forces Korea, 2019–2021

25 Josh Smith, “Home to 28,000 troops, South Korea unlikely to avoid a Taiwan Conflict,” Reuters, 26 September 2022,

26 Lee et al., KINU Unification Survey 2021, 41.

27 Min Joo Kim, “South Korea’s president skips Nancy Pelosi meeting due to staycation,” Washington Post, 4 August 2022,

28 Michelle Ye Hee Lee and Min Joo Kim, “South Korean conservative candidate wins close-fought, divisive presidential election,” Washington Post, 9 March 2022,

29 Jeong-Ho Lee, “South Korea Says Missile Shield ‘Not Negotiable’ with China,” Bloomberg, 11 August 2022,

30 Dongwoo Kim, “The Politics of South Korea’s ‘China Threat’,” The Diplomat, April 2021,

31 “China, S Korea made substantial program for 2nd phase FTA talk: China’s Ministry of Commerce,” Global Times, 21 July 2022,

32 Kim Sang-Min, “U.S. Lifts Missile Limits on South Korea,” Arms Control Today, June 2021,

33 Gabriel Dominquez, “North Korea provocations boosting U.S., Japan and South Korea security cooperation,” Japan Times, 6 October 2022,

34 Jo He-rim, “Foreign Minister to meet with victims of Japan’s forced labor,” Korea Herald, 31 August 2022,

35 “Japan, S. Korea to accelerate consultations over wartime labor issue,” Kyodo News, 4 August 2022,

36 “Japan Officially Ousts South Korea from Export Whitelist,” Nikkei Asia, 28 August 2019,

37 Kang Seung-woo, “Japan opposes Korea’s G7 participation,” Korea Times, 29 June 2020,

38 Will Fee, “Kishida Cabinet’s approval rating falls as headwinds mount,” Japan Times, 8 August 2022,; and Kim Yoo-chul, “Yoon’s poor support rate burdens his foreign policy,” Korea Times, October 2022,

39 Martin Weiser, “Did South Korea’s left help Yoon Suk-yeol win the presidency?,” East Asia Forum, 29 April 2022,

40 Scott A. Snyder, “South Korea’s Presidential Election: What to Know,” Council on Foreign Relations, 3 March 2022,

41 Darcie Draudt, “What President Yoon Suk-yeol’s Election Means for South Korean Democracy,” The Diplomat, 23 March 2022,

42 “DP Floor Leader Criticizes Yoon’s Liberation Day Speech,” KBS World, 16 August 2022,

43 “H.R.4346 - 117th Congress (2021–2022): Supreme Court Security Funding Act of 2022,” 9 August 2022,

44 Morgan Chalfant, “McConnell threatens semiconductor bill, prompting White House rebuke,” The Hill, 30 June 2022,

45 Victor Cha, “The Unintended Consequences of Success: U.S. Retrenchment from Korea?,” Korea Journal of Defense Analysis 31, no. 2 (June 2019), 165–91.

46 The author served as an Indo-Pacific geopolitical strategist on the Headquarters Staffs of United Nations Command, Combined Forces Command and US Forces Korea 2019–2021.

47 Andrew Glass, “U.S. recognizes communist China, Dec. 15, 1978,” Politico, 15 December 2018,

48 Carter left the alliance without proffering any security guarantee.

49 Charles Kraus “Nixon’s 1972 Visit to China at 50,” Sources and Methods (blog), 21 February 2022,

50 Snyder, South Korea at the Crossroads, 230

51 Laura Silver, Christine Huang, and Laura Clancy, “How Global Public Opinion of China has shifted in the Xi Era,” Pew Research, 28 September 2022,

52 Andrew Salmon, “Korea still taking Chinese hits over US missiles,” Asia Times, 6 December 2019,

53 William Gallo, “Worse than MAGA—South Korea Erupts Over Biden’s Trade Policy,” VOA News, 14 September 2022,

54 “Text - H.R.5376 - 117th Congress (2021-2022): Inflation Reduction Act of 2022,” 16 August 2022,

55 Gallo, “Worse than MAGA.”

56 Sue Mi Terry, “Yoon’s Strong Start in Foreign Policy,” Foreign Policy, 18 August 2022,

57 Gallo, “Worse than MAGA.”

58 Victor Cha, “The Meaning of GSOMIA Termination: Escalation of the Japan-Korea Dispute,” CSIS, 22 August 2019,

59 Yen Nee Lee, “The Japan-South Korea dispute could push up the price of your next smartphone,” CNBC, 23 July 2019,



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