China’s expanding military capabilities and escalating intimidation strategy against Taiwan have triggered growing concerns amongst Indo–Pacific democracies about the potential for Beijing taking military action against Taipei. Japan has described the deteriorating regional security situation as “severe and complex as it has ever been since the end of World War II,” with the international community “facing the greatest post-war trial yet and has entered a new era of crisis.”REF

In recent years, senior Japanese officials strongly criticized Chinese transgressions and issued bold public statements directly linking Japan’s national interests to protecting Taiwanese security, even hinting at military support during hostilities.

For several regional capitals, Russia’s invasion of Ukraine in 2022 was a wake-up call to the fact that similar hostilities could occur in the Indo–Pacific. As a result, the Japanese populace abandoned long-standing pacifist resistance to expanding the role of Japan’s Self-Defense Forces and whole-heartedly supported the Kishida Administration’s sweeping defense reforms announced in December 2022. Tokyo’s pledge to double its defense spending to 2 percent of national gross domestic product (GDP) and declared intent to develop counter-strike capabilities were a revolutionary break from decades of constricted defense posture and glacial decision-making—but itself may be insufficient, given the deteriorating security environment and the rising threats from both North Korea and China.

In sharp contrast, South Korea has limited its public remarks to—cryptically—criticizing Chinese actions in the East and South China Seas without directly naming Beijing as the perpetrator. Seoul avoids mentioning Taiwan contingencies and even criticized current and former senior U.S. military officials who suggested that South Korea had strategic interests and a potential role in defending Taiwan.

Seoul’s reticence is due to its laser focus on the North Korean threat, fear of economic retaliation from China (its largest trading partner), and the perception that Taiwan is far away and not a South Korean responsibility. Chinese action against Taiwan, however, would have significant and potentially cataclysmic impacts on South Korea’s economy and security.

While few officials or experts advocate a direct South Korean military role in or near Taiwan, U.S. expectations are that Seoul would need to assume greater responsibility for its own defense as well as provide enhanced rear-area support and extended reconnaissance and protection to U.S. forces engaged in Taiwan operations.REF

The U.S. will continue to advocate that allies and partners assume greater responsibilities for their own defense as well as assuming larger roles to address common security challenges beyond their borders. In return, Washington must procure sufficient military capabilities and make absolutely clear, to friend and foe alike, that it will resolutely uphold its long-standing security commitments to its allies.

South Korea Reluctant to Discuss Taiwan Contingencies

As to be expected, South Korea has prioritized its defense posture toward the escalating North Korean military threat. Taiwan has not been a general topic of discussion amongst the South Korean public or policy community since it seems far removed from Korean security concerns. Until Russia’s invasion of Ukraine raised fears of a similar Chinese attack in the Indo–Pacific, South Korean officials and experts had been extremely reluctant to discuss Taiwan contingencies, particularly any potential role for South Korea or U.S. forces stationed on the Korean Peninsula.

America’s allies, reliant on Washington for part of their defense, typically harbor anxieties of abandonment or entanglement. For South Korea, American involvement in the defense of Taiwan could simultaneously engender both fears.

Any reduction of American forces in South Korea, or U.S. involvement in large-scale military operations off-peninsula, would trigger South Korean fears of abandonment by its treaty ally to face the North Korean threat alone. South Koreans would be gravely concerned that Washington would no longer be willing or able to fulfill its commitments to existing war plans for the defense of South Korea. A perceived weakening of the U.S. security commitment might also embolden Pyongyang to engage in coercion, greater provocations, and direct attacks.

U.S. involvement in a military conflict over Taiwan would concurrently generate South Korean alarm at being entangled in a war with China. South Koreans worry that if the U.S. used its bases in South Korea to stage attacks on Chinese forces, it could trigger Chinese attacks on South Korea. Conversely, a South Korean refusal to be involved in a Taiwan crisis could lead to a degrading or severing of the alliance with Washington.

Even if China did not directly attack South Korean or U.S. bases in South Korea during a Taiwan conflict, Beijing would likely target U.S. facilities in Guam. At that point, Washington might demand South Korean involvement by invoking the U.S.–South Korea Mutual Defense Treaty in which both countries recognize “that an armed attack in the Pacific area on either of the Parties in territories now under their respective administrative control…would be dangerous to its own peace and safety and declares that it would act to meet the common danger.”REF

Debating Strategic Flexibility. When determining the potential role of U.S. Forces Korea (USFK) in the defense of Taiwan, both Washington and Seoul might cite a 2006 bilateral joint statement on strategic flexibility.

During the George W. Bush Administration, Washington declared it would withdraw U.S. forces from South Korea for redeployment to Iraq under a policy of strategic flexibility to move units where they were most needed. Secretary of Defense Donald Rumsfeld also publicly considered altering the U.S. force posture in South Korea as part of the Global Defense Posture Review. Both measures unnerved South Korea. Seoul tried to prevent U.S. forces from departing the peninsula since it feared the units might not return to Korea after their deployment to Iraq, which ultimately proved to be the case.

South Korea was also concerned that any U.S. military units redeployed from Korea to a Taiwan contingency or Korean support to U.S. operations would be deemed by China as grounds for attacking South Korea. In March 2005, President Roh Moo-hyun declared that South Korea “will not be embroiled in any conflict in Northeast Asia against our will. This is an absolutely firm principle we cannot yield under any circumstance.”REF

Eventually, the two governments papered over their differences by acknowledging each other’s interpretation. In January 2006, Secretary of State Condoleezza Rice and Foreign Minister Ban Ki-moon signed an agreement in which:

[South Korea] fully understands the rationale for the transformation of the U.S. global military strategy, and respects the necessity for strategic flexibility of the U.S. forces in [South Korea]. In the implementation of strategic flexibility, the U.S. respects the [South Korean] position that it shall not be involved in a regional conflict in Northeast Asia against the will of the Korean people.REF

Since then, there has been an underlying tension between expanding the role, responsibilities, and geographic scope of the alliance while maintaining the alliance’s primary focus on the defense of South Korea. Successive U.S. Presidents and Congress have pledged to maintain U.S. forces at the existing 28,500 troop level and repeatedly affirmed the U.S. extended deterrence guarantee to use all necessary means, including nuclear weapons, to ensure the defense of South Korea.

Seoul Leans Forward...a Little

South Korea espouses the necessity of upholding a rules-based international order, human rights, democratic values, and a free and open Indo–Pacific. Yet, Seoul has been reluctant to directly criticize those nations that violate those principles. Nor has it defined the measures it would undertake to uphold those values against regional threats. South Korean rhetoric and actions remain more reserved than those of other U.S. allies.

South Korea has gradually become more forthright in articulating its concerns about a potential military contingency in the Taiwan Strait and publicly voicing support for Taiwan against growing Chinese intimidation. Seoul has now increasingly defined Taiwanese security as affecting that of South Korea as well as linking it to regional and even global stability.

During the U.S.–South Korea May 2021 summit in Washington, Presidents Joe Biden and Moon Jae-in issued a joint statement that emphasized “the importance of preserving peace and stability in the Taiwan Strait.”REF First Vice Foreign Minister Choi Jong-kun commented that it represented Seoul’s view that Taiwan’s security has “a direct impact on our national interest.”REF South Korean officials stressed that it was the first time that Taiwan had been included in a U.S.–South Korean joint statement.

However, the statement was disappointing in comparison with the declaration from the previous month’s visit by Japanese Prime Minister Yoshihide Suga in which Japan directly criticized Chinese human rights violations in Hong Kong and Xinjiang Province, intimidation against Taiwan, and Beijing’s belligerent actions in the East and South China Seas.

By contrast, South Korea only blandly affirmed opposition to Chinese actions while refusing to mention China by name. The Biden Administration had tried to convince President Moon to accept stronger language against China but to no avail.REF

South Korean officials subsequently downplayed the significance of including Taiwan in the joint statement. When asked by journalists if Beijing might respond strongly, Foreign Minister Chung Eui-yong stressed that the Taiwan issue was expressed only “in generalities.”REF He added that, “We are fully aware of the unique relations between China and Taiwan. Our government’s stance has not changed.”REF First Vice Foreign Minister Choi Jong-kun believed that Beijing would appreciate that the summit did not specify China.REF

Upon his inauguration in May 2022, President Yoon Suk Yeol declared that South Korea’s policy of “strategic ambiguity,” in which Seoul tried to balance its security and economic relationships with the U.S. and China, would be replaced by “strategic clarity.” Yoon criticized his predecessors for timid deference to China out of fear of economic coercion and retaliation.REF

Instead, Yoon rejected Moon’s attempts at fence-sitting between China and the United States and declared that South Korea must never compromise on its core security interests. He vowed that Seoul would implement values-based policies and strengthen its alliance with the United States to provide a foundation and greater leverage when engaging China and North Korea. Relations with Beijing were to be based on mutual respect without Chinese economic arm-twisting.

Yoon also pledged that South Korea would become a “Global Pivotal State,” which “advances freedom, peace, and prosperity through liberal democratic values and substantial cooperation,”REF including assuming a greater international security role to defend democracies against attack or coercion. Yoon vowed to join multilateral regional cooperative initiatives to contribute to the peace and stability of the Indo–Pacific and “maintain the freedom of navigation and over-flight in the region.”REF

As a result, there was far greater U.S. and South Korean policy alignment on the Indo–Pacific region. During their May 2022 summit meeting, Presidents Yoon and Biden affirmed their commitment to maintain peace and stability and reiterated the “importance of preserving peace and stability in the Taiwan Strait as an essential element in security and prosperity in the Indo–Pacific region.”REF Yoon took a step further than his predecessor by linking Taiwan security to that of the region. However, characteristically the U.S.–South Korea joint presidential statement did not mention China by name.

Yet, there remained clear constraints on how far Yoon was willing to go in risking Beijing’s ire over Taiwan. In August 2022, Yoon did not meet with Speaker of the House Nancy Pelosi (D–CA) after her trip to Taiwan triggered angry Chinese statements and extensive military exercises. Yoon’s unwillingness to have an in-person meeting was explained by the presidential office as based on a “comprehensive consideration of national interest”REF but interpreted as timidity in aggravating Beijing.

In December 2022, the Yoon Administration released South Korea’s first “Strategy for a Free, Peaceful, and Prosperous Indo–Pacific Region.” The document underscored “the importance of peace and stability in the Taiwan Strait for the peace and stability of the Korean Peninsula and for the security and prospering of the Indo–Pacific.”REF When announcing the Indo–Pacific strategy, Yoon said “any unilateral change in the status quo by force should never be tolerated.”REF

But Seoul’s Indo–Pacific strategy had only one mention of China, and it was in a positive context as a “key partner for achieving prosperity and peace in the Indo–Pacific [with which Seoul] will nurture a sounder and more mature relationship as we pursue shared interests based on mutual respect and reciprocity, guided by international norms and rules.”REF By contrast, Japan’s national security documents released the same month were highly critical of China’s transgressions.

During an April 2023 interview, Yoon characterized tensions between China and Taiwan as a “global issue” and asserted that South Korea, together with the international community [would] absolutely oppose such a change.”REF Yoon, however, did not indicate what steps Seoul would be willing to undertake in a Taiwan contingency.

The August 2023 U.S., South Korean, and Japanese summit at Camp David affirmed trilateral agreement of “the importance of peace and stability across the Taiwan Strait as an indispensable element of security and prosperity in the international community.”REF For the first time, South Korea agreed to language criticizing China’s “dangerous and aggressive behavior” in the South China Sea.REF But the leaders did not go beyond a commitment to expeditiously consult with each other to coordinate responses to “regional challenges, provocations, and threats affecting collective interests and security.”REF

While President Yoon has incrementally strengthened South Korea’s messaging on China, South Korea’s progressive opposition party remains firmly committed to acquiescing to Chinese pressure tactics. During a March 2024 speech, Lee Jae-myung, leader of the Democratic Party, asked, “Why keep pestering China [and] why are we meddling everywhere?” He questioned the relevance of the Taiwan Strait to South Korea: “Whatever happens in the Taiwan Strait, whatever happens with China and Taiwan’s domestic issues, what does it matter to us?”REF In July 2024, the South Korean opposition parties vowed to introduce legislation to prevent the South Korean military from intervening in a crisis over Taiwan.REF

If Lee Jae-myung or another progressive Democratic Party candidate wins the South Korean presidential election in 2027, Seoul would likely distance itself from Washington and Tokyo while striving to improve relations with Beijing and Pyongyang.

The Strategic Importance of Taiwan to South Korea

South Korea’s economy is heavily reliant on trade, supply chains, and maintaining freedom of navigation for imports and exports. South Korea and Taiwan are each other’s fifth-largest trading partners.REF More than 90 percent of South Korea’s maritime trade volume passes through the Taiwan Strait and the South China Sea.REF

Taiwanese fabrication facilities produce 60 percent of the world’s semiconductors and 92 percent of the most-advanced logic chips.REF According to Bloomberg Economics, a Chinese invasion of Taiwan would cost the global economy around $10 trillion, approximately 10 percent of global GDP, while a Chinese blockade of Taiwan would result in a loss of $5 trillion to the global economy.REF A China–Taiwan conflict could reduce South Korea’s GDP by an estimated 23.3 percent.REF

Beyond the physical and economic devastation of a military clash, a Chinese victory over Taiwan would enable Beijing to subsequently project military power against and undermine the security of other Indo–Pacific democracies, including South Korea and Japan. U.S. and Japanese military capabilities are crucial for the defense of South Korea. A dominant Chinese sphere of influence would incentivize Beijing to attempt to dictate terms to its neighbors who would be less able and willing to resist Chinese coercion.

Despite Taiwan’s critical importance to South Korea, Seoul remains reluctant, if not resistant, to defining the role it would play in a crisis in the Taiwan Strait. The predominant South Korean concern is being dragged into “someone else’s conflict.” Ideally, Seoul should be prepared to assist the international community to protect South Korean strategic interests in the Indo–Pacific.

South Korea needs to embody its Global Pivotal State role rather than seeking to remain aloof from potential contingencies that would directly affect its national security. Having pledged to preserve stability in the Taiwan Strait, Seoul should articulate how it will do so rather than relying on others to defend its strategic interests.

The South Korean public supports a South Korean role in a Taiwan crisis. According to an August 2022 survey conducted by South Korean daily Joongang Ilbo and the East Asia Institute, 64.5 percent of South Korean respondents agreed that Seoul should provide direct or indirect support for U.S. military operations in a Taiwan contingency. Within that figure, 42 percent responded that South Korea’s military role should be limited to providing rear-area support for U.S. forces, and 22.5 percent supported participation in joint military operations with the U.S. Only 18 percent of respondents opposed any involvement of South Korea in a Taiwan contingency.REF

A subsequent poll in September and October 2023 indicated that 45.21 percent of South Korean respondents supported imposing economic sanctions on China after an attack on Taiwan while 34.39 percent supported providing military assistance.REF

The Risks of Non-Involvement

There would certainly be risks for South Korea if it became involved in a multilateral coalition to defend Taiwan. China may inflict economic retaliation or even attack U.S. or South Korean bases. However, there are also tangible costs of not supporting an international defense of Taiwan.

South Korea exists today because 70 years ago an international coalition defended it against attack and guaranteed its sovereignty. Seoul should consider doing for Taiwan what others did for its nation 70 years ago.

Seoul should consider what would happen if other nations were to now refrain from providing support to South Korea after another major North Korean invasion, out of fear that doing so could anger China and lead to economic retaliation, or that it might involve combat against Chinese forces with potential direct attacks on their countries.

South Korean reluctance to defend another democracy could have significant repercussions for its alliance with the United States. U.S. policymakers and the American public might question the continued value and relevance of its military relationship with South Korea if Seoul attempted to sit on the sidelines—or, especially, to restrict the use of U.S. forces stationed in South Korea.

Any attack on U.S. forces in South Korea or potentially elsewhere in Asia would, in the U.S. view, require a South Korean response against China. A South Korean refusal to defend U.S. forces would be seen as a failure to abide by, or an abrogation of, the mutual defense treaty. Such inaction by South Korea would likely end the alliance.

Seoul Needs to Look Beyond the Korean Peninsula

Presidents Biden and Yoon pledged that they would upgrade the bilateral military relationship to a comprehensive strategic alliance based on shared values and interests that would promote peace and stability in the Indo–Pacific.REF Some U.S. officials have suggested that the U.S.–South Korea alliance should operationalize broader responsibilities for the military relationship in the Indo–Pacific.

In July 2022, General Paul LaCamera, Commander of U.S. Forces Korea, Combined Forces Command, and United Nations Command (USFK/CFC/UNC), recommended that, while remaining anchored on the North Korean threat, the bilateral alliance should also evolve into a “multinational and multidimensional coalition [to] maintain a rules-based international order with an eye on China and Russia.”REF

LaCamera assessed that Taiwan contingencies would not remain local and would quickly “become regional and global pretty quickly [with] second and third-order effects elsewhere.”REF He commented that the U.S. is considering a contingency plan to support South Korea’s role in defending Taiwan in the event of a Chinese invasion.REF

In a September 2022 interview, General (ret.) Robert Abrams, the Commander of USFK/CFC/UNC from 2018 to 2021, concurred that the United States will keep open “all options” in deciding which forces might be used in the event of a military conflict between China and Taiwan, “including those assigned to the USFK.”REF

Such advocacy, however, comes with caveats. General Vincent Brooks, the Commander of USFK/CFC/UNC from 2016 to 2018, commented that “defending [South Korea] has to be the first task and so, even as the alliance continues to think beyond the peninsula, it must never lose sight of the peninsula. So defending there first against the immediate North Korea threat has to be the first concern.”REF

Similarly, General Walter “Skip” Sharp, USFK/CFC/UNC Commander from 2008 to 2011, commented, “We are still going to have to deter North Korea if China attacks Taiwan. With what little U.S. combat power we have stationed in Korea, I do find it hard to believe that we would pull our forces out of Korea to deal with a Taiwan contingency.… [T]he challenge will be what additional forces we could send to Korea if needed.”REF

North Korean Threat Looms Large for Seoul

While other Indo–Pacific democracies are predominantly focused on the growing Chinese threat, South Korea prioritizes its security posture against North Korea, which poses an existential threat. While South Korean military forces have participated in off-peninsular operations in the past—such as Vietnam, Afghanistan, and Iraq—South Korean officials rebuffed possible involvement in a Taiwan crisis.

In September 2022, President Yoon stressed that in the case of a military conflict over Taiwan, “there would be increased possibility of North Korean provocation [and] the top priority for Korea and the U.S. Korean alliance on the Korean peninsula would be based on our robust defense posture, [so] we must deal with the North Korean threat first.”REF

Defense Minister Shin Won-sik commented that “if a crisis occurs in Taiwan, the South Korean military’s paramount concern is observing the possibility of North Korean provocations and working with USFK (US Forces Korea) to establish a firm joint defense posture.”REF Vice Defense Minister Shin Beom-chul denied that there had been any bilateral discussions with the U.S. on Taiwan contingencies. Shin emphasized that any bilateral contingency planning “would not move in a direction that undermines security on the Korean Peninsula.”REF

Seoul Considers Its Options

In choosing how to respond to a Taiwan crisis, South Korea would have to balance upholding its diplomatic, economic, and security interests with the potential risks, costs, and consequences of becoming involved.

Seoul would consider the consequences of refusing U.S. requests to assist the international community to defend Taiwan, which could sever the alliance with the risk that acceding could trigger Beijing to attack U.S. bases, or even South Korean bases or cities. South Korea may perceive that Washington is asking it to risk its survival for that of Taiwan or defending the existing regional security order.

The danger of horizonal escalation is also very real. Either acting in concert with Beijing, or independently sensing an opportunity to achieve its own objectives, Pyongyang might decide to escalate provocative actions or initiate hostilities against South Korea. Conflicts on Taiwan and the Korean Peninsula could either occur simultaneously or sequentially.

Even prior to the outbreak of hostilities, Seoul would see a dilemma between the merits of strong South Korean rhetoric and actions potentially deterring a Taiwan crisis with fears of Chinese economic retribution for even a public declaration of support to Taiwan prior to hostilities.

South Korean support to Taiwan may not be an all-or-nothing decision but a graduated and escalating response, a rheostat instead of an on-off switch. Seoul’s decision would be heavily dependent on the scenarios, which include China conducting:

1. An enhanced gray-zone operation, including maritime incursion and interdiction, sabotage, cyber operations, and influence campaign;
2. A blockade of Taiwan to impose economic damage;
3. A missile attack on, but not invasion of, Taiwan to induce Taipei to negotiate; and
4. A full-scale invasion of Taiwan, either with or without attacking U.S. bases in Japan, South Korea, and the Indo–Pacific region.

U.S. Expectations of South Korea During a Taiwan Crisis

Discussions with current and former U.S. officials and alliance managers indicate that Washington sees South Korea’s primary responsibility during a Taiwan crisis as assuming a larger role in deterring and defeating North Korean attacks while also providing indirect military assistance through rear-area support, protection, and expanded reconnaissance for U.S. military operations in defense of Taiwan.REF

If China initiated a naval blockade of Taiwan, Seoul should safeguard the freedom of navigation that is vital to South Korea’s economic survival by providing naval forces to defend sea lines of communication, escort and protect ships transiting the Taiwan Strait, and break the Chinese blockade.

If China attacked Taiwan, South Korea would be expected to publicly and strongly condemn Chinese actions; participate in international sanctions against Beijing; impose its own unilateral economic punitive measures, including trade bans and denial of Chinese ships and planes transit of Korean airspace or entry into Korean ports; allow the U.S. forces in South Korea to engage in Taiwan operations; and to endorse, if not participate in, an international military response.

South Korean military responses would be called upon to:

• Conduct intelligence, surveillance, and reconnaissance against Chinese ships and planes operating near the Korean Peninsula.
• Provide rear-area and logistical support to U.S. forces conducting reception, staging, onward movement, and integration (RSOI) operations in South Korea.REF This could include providing full-time security for U.S. bases that is currently provided by U.S. forces; assuring access to South Korean ports and airfields; providing transport assistance for the flow of U.S. ammunition, logistics, and forces onward to Taiwan; conducting maintenance and repair of U.S. weapons systems; and providing munitions, ammunition, and military-grade fuel.
• Defend South Korean and U.S. forces from, and respond to, Chinese attacks. South Korea should extend its air and maritime protection for U.S. forces against potential Chinese attacks. If Beijing attacked U.S. bases in South Korea, Seoul would be obligated under the bilateral defense treaty to respond against China. Washington may stipulate that Chinese attacks on U.S. bases in Guam or throughout the Indo–Pacific would also require a South Korean response.
• Assume greater responsibility for defending itself against North Korean attacks. Washington is unlikely to withdraw elements of U.S. military forces in South Korea from the peninsula for Taiwan operations, with the possible exception of some airplanes. U.S. ground forces in South Korea would be of little utility early in a Taiwan contingency and the numbers of U.S. Naval and Marine Corps personnel in South Korea are negligible. However, follow-on forces that are dual-apportioned for both Korean and Taiwan contingencies might be affected.

Recommendations for the United States and South Korea

Given the growing Chinese and North Korean military threats, there is a clear need to augment allied military capabilities, increase production of ammunition and munitions, increase reserves of ammunition and missiles, and strengthen multilateral coordination and integration of contingency planning, intelligence-sharing, maritime domain awareness, and capacity building.

To address these requirements, the United States should:

Re-Affirm Its Commitment to America’s Indo–Pacific Allies and Partners. Japan, South Korea, the South China Sea, and Taiwan are of vital economic and geopolitical importance to the United States. A defeat in any of those areas would have a devastating effect on U.S. and allied strategic interests and fundamentally alter the regional, if not global, military, diplomatic, and economic balance of power. A failure by the United States to uphold its commitments to its Indo–Pacific allies and security partners would have a deleterious effect on regional security and stability, weaken deterrence, undermine the credibility of America’s security guarantees, and embolden opponents to test American resolve.

Even a perceived degradation in U.S. commitment to defend its allies and partners could undermine efforts to rally other Asian nations to resist Chinese demands and prompt them to adopt a more conciliatory approach to Beijing. The viability of the U.S. extended deterrence guarantee is demonstrated by the presence of U.S. forces, robust military exercises with allies and regional partners, and rotational deployment of U.S. strategic assets—including strategic bombers, dual-capable aircraft, submarines, and carrier-strike groups.

Strengthen Its Military Posture in the Indo–Pacific. Washington needs to substantially increase deterrent and response capabilities for Korea, South China Sea, and Taiwan contingencies. Washington needs sufficient air, ground, Marine, and Naval forces in the region to sustain major conflicts. The U.S. needs greater investment to augment the quality and quantity of its conventional and nuclear forces.REF

The U.S. should assess the benefits of forward-deploying significant stockpiles of ammunition, missiles, and weapons in Japan, the Philippines, and South Korea for Indo–Pacific contingencies, given the difficulties of resupplying munitions across long distances during conflict.

Engage with Seoul to Define Roles and Missions for Korea and Taiwan Contingencies. Existing military operations plans should be reviewed in response to growing North Korean and Chinese military capabilities. Washington and Seoul should develop joint military plans for potential Korean and Taiwanese conflicts occurring singly, sequentially, and simultaneously, including Chinese military involvement on the Korean Peninsula and Korean involvement in the defense of Taiwan or as part of a broader war with China. Planning should delineate responsibilities for South Korean forces, U.S. Forces Korea, and follow-on U.S. units apportioned for Indo–Pacific contingencies. Future table-top exercises should test these plans, identify potential capability shortfalls, and provide recommendations for remedial action.

Bilateral consultations should identify and redress any differences in expectations as the United States and South Korea work to implement an agreed-upon comprehensive strategic alliance with expanded roles and missions beyond the Korean Peninsula. Contingency plans should be developed for Korea, Taiwan, and South China Seas contingencies ranging from maritime restriction and blockade to full-scale conflict.

Expand Allied Cooperation on Defense Development and Production. Combat operations in Ukraine underscored the high expenditure rate of munitions in modern combat. Conflict on the Korean Peninsula or near Taiwan would rapidly deplete U.S. ammunition and missile reserves. Washington must address constraints that hinder increasing indigenous U.S. production of necessary weapons and ammunition.REF

In addition, the U.S. should intensify its efforts to expand military co-development and co-production with allies and partners to replenish depleted reserves and prepare for potential conflicts in the Indo–Pacific. South Korea is an obvious candidate given its world-class defense industry, highly advanced production capabilities, and long-standing military relationship with the United States. South Korea is currently the world’s ninth-largest global arms exporter and President Yoon announced that Seoul aims to become the world’s fourth-largest defense equipment exporter.REF

In April 2024, the U.S. and South Korea agreed to jointly develop advanced defense technologies as well as create a Regional Sustainment Framework to facilitate logistics in a contested environment as well as cooperation to distribute maintenance, repair, and overhaul capabilities in the Indo–Pacific.REF The two countries have also been working toward a Reciprocal Defense Procurement agreement to promote interoperability of defense equipment, develop and manufacture weapons jointly, and strengthen defense supply chains.REF

Washington should reduce restrictions, regulations, and export controls—such as International Traffic in Arms Regulations (ITAR) restrictions—to allow greater joint weapons development, technology transfer, and collaborative research and development. A high priority should be placed on licensing the production of precision-guided missiles to augment allied stocks.

Expand Multilateral Security Architecture for Indo–Pacific Contingencies. Regional security threats require regional responses. Allies and partners are force multipliers as the U.S. leads coalitions of nations against common threats. Addressing the Chinese threat to the Indo–Pacific requires regional nations to significantly augment their indigenous military capabilities; to assist lesser capable nations in security capacity-building, including maritime domain awareness and naval interdiction capabilities; and to accelerate efforts for integrating partners into collective regional security networks.

New multilateral security coalitions supplement the existing U.S. “hub and spoke” alliance system to create a network for coordinating crisis management and military collaboration to deal with different components of the China threat. The U.S. and its allies should undertake multilateral contingency planning on Taiwan and South China Sea scenarios. Future multilateral military exercises could quietly incorporate Taiwan contingencies.

Augment the Security Dialogue with Taiwan. The United States and its regional partners should increase communication, intelligence-sharing, and operational contingency planning with Taiwan. While most U.S. regional partners take a highly risk-averse stance toward political and military contact with Taipei and could be overly sensitive, nations could use coast guards and air traffic control authorities as initial proxies for coordinating maritime and aerial surveillance and reconnaissance, situational awareness, and real-time intelligence exchanges of Chinese military movements in the East and South China Seas. Japan’s recent joint Coast Guard exercise with Taiwan serves as a promising model.REF

This effort could build on the Quad’s Indo–Pacific Partnership for Maritime Domain Awareness (IPMDA) announced in May 2022. The initiative seeks to develop a near-real-time, integrated, and cost-effective maritime domain awareness network across the Pacific Islands, Southeast Asia, and the Indian Ocean regions.

A positive development took place in June 2024 when the U.S., South Korean, and Japanese coast guards conducted their first trilateral training exercises off the western coast of Japan. The training followed a May 2024 trilateral agreement to “enhance maritime expertise and promote regional cooperation” in the Indo–Pacific as well as enhance multilateral operations with other partners in the region.REF

South Korea should:

Strengthen Its Offensive and Defensive Military Capabilities. Seoul should maintain ongoing efforts to procure additional advanced attack aircraft and develop missiles with larger payloads and ranges. President Yoon pledged to strengthen South Korean capabilities to implement the Kill Chain pre-emptive-attack strategy and the Massive Punishment and Retaliation strategy against North Korea. The Ministry of Defense announced plans to increase its inventory of land-based, sea-based, and air-based precision missiles, augment penetration and strike capabilities of special forces, and procure additional F-35 stealth fighter jets.

South Korea should also improve its command, control, and communication system to enable enhanced joint and combined capabilities as well as continue deployment of its Cheongung II medium-range surface-to-air missile (SAM) and long-range SAM (L-SAM) programs to augment existing Patriot and Terminal High Altitude Area Defense (THAAD) land-based missile defenses. Seoul should carry through on plans to deploy SM-6 missiles on its Aegis-equipped KDX-III destroyers to defend the country against North Korean submarine-launched ballistic missiles.

Publicly Underscore the Strategic Importance of Taiwan to South Korean National Interests. The Yoon Administration should engage with and educate the populace on the consequences to South Korea if China were successful in dominating Taiwan through economic coercion, low-intensity conflict, or large-scale military force. Emphasis should be placed on the economic interdependence of South Korea with regional trading partners, such as Taiwan, as well as the importance of maintaining freedom of navigation in the Indo–Pacific for South Korea’s trade-based economy. Public awareness should also be raised of the detrimental effect that Seoul’s seeking to avoid supporting Taiwan would have on the alliance with the United States as well as future international support in response to a North Korean invasion.

Assume a Larger Security Role in the Indo–Pacific. While remaining predominantly focused on the North Korean threat, South Korea has a formidable, highly capable military to implement President Yoon’s pledge for his country to become a Global Pivotal State by shouldering greater responsibilities for addressing regional security challenges. The Yoon Administration should assess how to contribute to ensuring freedom of navigation in the South China Sea as well as potential contingencies in the Taiwan Strait. Seoul should augment security ties with regional democracies and expand its involvement in regional exercises on air and sea interdiction, anti-submarine warfare, coastal defense, maritime surveillance, and operating as a combined task force for multiple Indo–Pacific contingencies.

Conclusion

Even during a Taiwan crisis, the United States would remain inextricably bound to the defense of South Korea by its bilateral defense treaty commitments, continued integrated role in the U.S.–South Korea Combined Forces Command structure, existing bilateral operation and contingency plans, and its duties as Commander of United Nations Command. Beyond its formal obligations, maintaining stability in northeast Asia remains a core U.S. strategic interest. To address security threats in the Indo–Pacific, the United States, its allies, and its partners need to implement an extensive campaign to augment their military forces, increase co-development and co-production of weapons and munitions, and enhance multilateral security cooperation.

Bruce Klingner is Senior Research Fellow for Northeast Asia in the Asian Studies Center at The Heritage Foundation.