Successful U.S.–South Korean Summit Strengthened the Alliance

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Successful U.S.–South Korean Summit Strengthened the Alliance

May 5, 2023 10 min read Download Report
Bruce Klingner
Senior Research Fellow, Northeast Asia
Bruce Klingner specializes in Korean and Japanese affairs as the Senior Research Fellow for Northeast Asia.


During his speech to Congress, South Korean President Yoon Suk Yeol cited the inscription at the Korean War Veterans Memorial in Washington: “Our nation honors her sons and daughters who answered the call to defend a country they never knew and a people they never met.” It is a fitting reminder that freedom must be defended—even at the cost of sending so many young men and women into harm’s way. The U.S.–South Korean alliance was forged in blood in the crucible of war, but the two countries are far more than a military alliance: They share values, principles, and interests far beyond the shores of the Korean Peninsula. South Korea’s growing capabilities and influence let it play a stronger regional and global role—lightening the load for America as it faces growing challenges in the Indo–Pacific.

Key Takeaways

South Korean President Yoon’s visit to Washington with President Biden—including an address to a joint session of Congress—re-enforced the U.S.–South Korea alliance.

South Korea has proven itself a stalwart ally to the U.S., and given the threat from North Korea and China, Seoul is prioritizing its relationship with Washington.

Both countries should expand combined military exercises and regional security relationships, and operationalize the Nuclear Consultative Group.

South Korean President Yoon Suk Yeol’s trip to Washington from April 24 to 28 highlighted the importance of an indispensable American ally and provided the springboard for even greater bilateral security, economic, and diplomatic cooperation. Yoon’s state visit was the first by a South Korean president in 12 years and the first address to a joint session of Congress in a decade. Presidents Yoon and Joe Biden emphasized closely aligned policies based on shared national values, principles, and objectives while affirming defense against regional and global security challenges.

Washington rolled out the red carpetREF for Yoon who reciprocated with masterful speeches showcasing the renewed vitality of the bilateral alliance, which is particularly apropos during the 70th anniversary year of both the armistice ending the Korean War and the inception of the mutual defense treaty. Since then, the allies have remained shoulder to shoulder, not only out of tradition and honor, but due to necessity, since the North Korean and Chinese threats are even more dire today.

Seoul Prioritizes Relationship with Washington

Yoon’s speech to CongressREF paid homage to the U.S. support during the Korean War and in decades afterward that enabled South Korean rebuilding to become the economic “miracle on the Han” river. It is the only nation to have gone from economic aid recipient to donor. Yoon also described the vibrant and growing bilateral economic, trade, and investment partnership.

Upon his inauguration in May 2022, President Yoon declared that he would strengthen South Korea’s alliance with the United States to provide a firm foundation and leverage for Seoul’s engagement with Pyongyang and Beijing. He adopted a pragmatic policy toward North Korea by offering an “audacious initiative”REF of economic aid conditioned on progress toward a denuclearization accord.

Until Pyongyang agrees to resumption of dialogue, Seoul will continue to enhance its military capabilities. Yoon acted on his early pledge to improve South Korea’s strained relations with Japan to enable greater trilateral security cooperation against the common North Korean and Chinese threats, including resumption last year of trilateral South Korean, Japanese, and U.S. military exercises.

Improving Alliance Readiness. North Korea was a major topic of discussion during the summit as the two countries agreed to concurrently press for resumption of diplomatic dialogue with Pyongyang while concurrently enhancing defenses against the regime’s growing nuclear and missile prowess. President Yoon, like President Biden, has rejected future summit meetings with North Korea without first attaining actual progress toward a denuclearization accord by diplomats.

Since their first meeting in Seoul last May, Presidents Yoon and Biden resumed large-scale bilateral combined military exercises to repair the damage to alliance deterrence and defense capabilities wrought by the unilateral U.S. decision in 2018 to cancel and constrain military drills. Since late 2022, Washington and Seoul have conducted wide-ranging air, naval, and ground maneuvers on and near the Korean Peninsula.

The U.S. and South Korea agreed earlier this year to conduct at least 20 large-scale combined training exercises in 2023. The Freedom Shield and Warrior Shield exercises in March 2023 were the largest and longest drills in at least five years.REF

Strengthening U.S. Extended Deterrence

The most notable achievement of the summit was the Washington Declaration that addressed U.S. concerns of allied nuclear proliferation and South Korean doubts about the viability of the American extended deterrence guarantee. The document comes in response to a surge in South Korean advocacy for an indigenous nuclear weapons program or redeployment of U.S. tactical weapons to the Korean Peninsula.

The United States agreed to a new bilateral Nuclear Consultative Group, pledged to consult with South Korean leadership on use of nuclear weapons on the Korean Peninsula, and to enhance nuclear information-sharing, planning, exercises, and cooperative decision-making.REF While not guaranteeing U.S. use of nuclear weapons in response to North Korean nuclear use, Washington affirmed that such North Korean action would lead to the end of the regime.REF

In return, South Korea affirmed its commitment to the Non-Proliferation Treaty and the bilateral U.S.–South Korean civilian nuclear agreement, as well as declaring its “full confidence in U.S. extended deterrence commitments,” thus firmly closing the door on an indigenous nuclear weapons program. Seoul also agreed to coordinate, if not indirectly integrate, its new Strategic Command with the U.S.–South Korean Combined Forces Command.

The accord is focused more on enhancing reassurance to Seoul than increasing deterrence to Pyongyang. Last year, the U.S. resumed rotational deployment of nuclear-capable strategic assets after a four-year hiatus. Since 2022, the U.S. has deployed strategic bombers, dual-capable fighter aircraft, submarines, and aircraft carriers to the Korean Peninsula. President Biden pledged to raise the visibility of strategic-asset deployments, including the first visit of a ballistic missile submarine to a South Korean port in 40 years.

Addressing the Growing Chinese Threat. Yoon has firmly aligned South Korea with the United States and other like-minded democracies in opposing China’s coercive tactics to intimidate Asian nations. In December, the Yoon administration released South Korea’s first Indo–Pacific strategy, delineating policies for South Korea to assume a more influential role to protect freedom, democracy, human rights, and the rules-based order in the Indo–Pacific.

During the summit, Presidents Yoon and Biden committed to an “inclusive, free, and fair-trading system [while opposing] economic coercion.”REF Washington and Seoul also committed to enhancing regional cooperation on maritime domain awareness and security.

However, while President Yoon has provided inspirational and aspirational remarks of upholding diplomatic values and principles, South Korea continues its timidity in directly calling out Chinese and Russian transgressions, particularly when compared with other Asian–Pacific democracies, such as Australia and Japan. While both South Korea and Japan have criticized Chinese human rights violations and intimidating actions against its neighbors, Seoul has repeatedly refrained from identifying Beijing as the perpetrator.

South Korean hesitancy in confronting authoritarian regimes is also evident in its reluctance to directly provide lethal aid to Ukraine out of concern of angering Moscow. The Yoon administration has adopted workarounds—such as “loaning” ammunition to the United States or selling weapons to Poland far in excess of Warsaw’s needs—to assist Ukraine while maintaining a policy of neutrality.

Enhancing Economic Ties. South Korea has sought to reduce its trade dependence on China and vulnerability to Chinese pressure by diversifying its economy toward other partners. Last year, South Korean firms announced several multibillion-dollar investment projects in the U.S. with more slated in the future. During the past two years, South Korea invested $100 billion in the United States and, since 2021, the U.S. has been the top destination for South Korean investment.REF

During Yoon’s visit, U.S. and South Korean firms signed 23 memoranda of understanding to increase cooperation in semiconductors, future vehicles, and clean energy.REF Washington and Seoul also signed agreements to expand supply-chain security, and to enhance cooperation for the critical-minerals supply and in biotechnology. Washington sought to remove a major irritant with Seoul by pledging to minimize investment uncertainty and management burdens caused by the 2022 Inflation Reduction Act (IRA) and the 2022 Creating Helpful Incentives to Produce Semiconductors (CHIPS) and Science Act, though no details were provided. The IRA does not appear compliant with the U.S.–South Korea (KORUS) free-trade agreement, and the CHIPS and Science Act is likely to constrain South Korean firms’ operations in China.REF

What Washington and Seoul Should Do

While the summit was successful, a number of follow-on actions are required. To ensure implementation of the agreements, Washington and Seoul should:

Operationalize the Nuclear Consultative Group (NCG). The Washington Declaration allayed Yoon administration concerns and enhanced allied reassurance. However, there remains strong advocacy in South Korea for an indigenous nuclear program. Washington and Seoul must flesh out the bare bones of the agreement to delineate policies, roles, and missions related to extended deterrence.

Post-summit variances in U.S. and South Korean descriptions of the nuclear agreement may be due to different interpretations, or nuances of technical terminology, or the Yoon administration overhyping what Seoul achieved. Deliberate or inadvertent differences of interpretation could cause trouble down the road when there is belated realization of a gap in perception. To avoid such confusion, the U.S. and South Korea should engage in extensive ongoing dialogue to ensure that both sides are in clear agreement.

In order to gain public support for the Washington Declaration, the Yoon administration should engage in a strategic messaging program to explain how greater integration with U.S. extended deterrence is more in South Korea’s interest than greater independence from the alliance.

Subsequently Multilateralize the NCG. While the initial emphasis should be on implementing the bilateral NCG, Washington and Seoul should eventually invite Australia and Japan to join as an additional means to incorporate U.S. allies in collectively addressing common threats to the Indo–Pacific region. Creating a new quadrilateral defense coordinating group among Australia, Japan, South Korea, and the U.S. would emphasize a cooperative approach between the U.S. and security partners in nuclear deterrence decision-making.

Augment the Size, Scope, Frequency, and Type of Combined U.S.–South Korean Military Exercises, Including U.S. Strategic Assets. The U.S. and South Korea should consider a return to pre-2018 training levels a minimum requirement for future training schedules. Given the escalating growth in North Korean nuclear and missile forces, as well as the regime’s extensive conventional force provocations in late 2022, Washington should confer with Seoul on the parameters of a training regimen and deployment of U.S. strategic assets—including strategic bombers, dual-capable aircraft, submarines, and carrier-strike groups—necessary to augment deterrence and reassure South Korea.

These exercises should increasingly include Japanese Self-Defense Forces and go beyond mere ballistic missile defense and anti-submarine exercises. Washington and Seoul should also encourage greater United Nations Sending State participation in peninsular military exercises.

Expand Regional Security Relationships. The Biden and Yoon administrations should strive to include South Korea in more multilateral dialogues within and beyond the Indo–Pacific region to enable a collective regional security network. Multilateral security initiatives would complement the U.S. “hub and spoke” alliance system to improve coordination and collaboration amongst partners across the Indo–Pacific.

Rather than creating formal security organizations, it would be more effective to have multiple, multilateral, multi-domain security initiatives throughout the Indo–Pacific with overlapping memberships focused on specific challenges. Such mission-oriented groupings can more readily make decisions and implement security actions.

Washington should:

Urge Seoul to Negotiate Visiting Force Agreements (VFAs) Between South Korea and All U.N. Sending States. A major Korean contingency would involve not only South Korean and U.S. forces, but also those of U.N. Sending States as occurred during the 1950-to-1953 Korean War. Yet, currently, there is not a single VFA or Status of Forces Agreement between a Sending State and South Korea due to Seoul’s refusal. All Sending State U.N. Command personnel are on rotation from their respective embassy in order to provide legal protection. The lack of VFAs would delay or prevent participation of Sending States to the defense of South Korea.


During his speech to Congress, President Yoon cited the inscription at the Korean War Veterans Memorial in Washington: “Our nation honors her sons and daughters who answered the call to defend a country they never knew and a people they never met.” It is a fitting reminder that freedom is not free, that it must be defended—even at the cost of sending so many young men and women into harm’s way.

The U.S.–South Korean alliance was forged in blood in the crucible of war, but the two countries are far more than a military alliance: They share values, principles, and interests far beyond the shores of the Korean Peninsula. South Korea’s growing capabilities and influence empower it to play a stronger regional and global role.

While America faces growing challenges in the Indo–Pacific, the load is lightened because it is shared with stalwart allies, such as South Korea.

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


Bruce Klingner
Bruce Klingner

Senior Research Fellow, Northeast Asia