The Present and Future of ROK-US Alliance: President Yoon

From Nuclear Power Sharing to Order Building: Transforming the US-South Korean Alliance

The state visit punctuates the alliance’s historical success and future trajectory. On the peninsula, the leaders will pivot toward nuclear power-sharing that stops just shy of sharing America’s nuclear weapons. South Korea will have a more prominent voice in nuclear planning and decision-making.

Regionally, the two allies are prepared to strengthen cooperation with Japan and other like-minded countries throughout the Indo-Pacific region. Beyond sharing missile data with Japan, it should be possible for South Korea to coordinate efforts with the AUKUS countries on advanced technologies that relate to hypersonic missiles and with the Quad countries regarding maritime domain awareness.

Internationally, the United States will support South Korea’s bid to be a global pivotal power. By supporting peace and stability across the Taiwan Strait and opposing Russia’s illegal attack on Ukraine, President Yoon is standing up for democracy and the rule of law. 


President Yoon Suk-yeol’s state visit underscores the alliance’s historical success while punctuating the pathbreaking trajectory of US-South Korea relations. An alliance forged in blood is set to work in tandem across nuclear deterrence, the defense of cyber and outer space, and the creation of a new digital economy and technological architecture.


The 70th anniversary of the 1953 Mutual Defense Treaty marks both a milestone and an inflection point. This is a special year for reflecting on the effort of so many Americans and South Koreans. It is little wonder that President Yoon’s visit to Washington and Boston this week includes multiple events commemorating—and never forgetting—wartime sacrifices.


The achievement of preserving peace on the peninsula after the Korean Armistice Agreement is remarkable. Alliance strength kept the peace and provided the long stability essential for the South Korean people to achieve the miracle on the Han. Koreans should be proud of their achievements, including a vibrant democracy and a world-leading economy.


But today's world is also starkly different from the early post-World War II period. Major power competition is resurgent. So is a new era of nuclear modernization. And these uncomfortable trends are occurring amid a fourth industrial age in which technological change will determine economic and military power. Meanwhile, accelerating climate change is marching forward on its scientific timeline, caring little about humanity’s inability to muster a sufficient response.


Because of our challenging era, the success of the US-South Korean alliance must now pivot on and from the peninsula to the more significant threats posed to the regional and global order. The pivot foot of the alliance will remain grounded in advancing capabilities and a tighter-than-ever level of defense cooperation to ensure that North Korea cannot fire its growing nuclear arsenal without risking its survival. 


Transforming the alliance for a peninsular pivot can help keep the peace locally, regionally, and globally while making substantial and tangible contributions to the prosperity and welfare of others.


The alliance pivot must occur on the peninsula, in the region, and globally.


A Pivot to Nuclear Power Sharing

On the peninsula, the most crucial task for the US-ROK alliance is to guarantee the preservation of deterrence despite Pyongyang’s unrelenting nuclear buildup.


The solid-fuel Hwasong-18 ICBM, the threat to deploy tactical nuclear weapons, the promulgation of a provocative nuclear law and doctrine, and Pyongyang’s growing array of missiles of all ranges and azimuths require Seoul and Washington to have an unquestionable and unified capability of imposing an existential threat to the Kim regime should it think about embarking on reckless aggression. 


Against Russia’s attempts to leverage potential nuclear use in Ukraine, North Korea seeks not only to become an “irreversible” nuclear-weapon state but a nuclear-weapon-use state. The result is a perceived erosion in America’s extended deterrence obligation, by which the United States pledges to South Korea that it will bring to bear the full range of its capabilities—including its longstanding nuclear superiority—to defeat aggression against our linchpin ally. The allies have tried to tailor extended deterrence to the evolving threat environment. In the meantime, the near-continuous deployment of strategic assets is meant to reassure the democracies and signal that nuclear use would end the Kim regime.


South Korea is technically capable of building an independent nuclear weapon. However, abandoning the nuclear nonproliferation treaty and building a South Korean nuclear program would inject disunity into an ironclad alliance, massively disrupt trade and investment, and grievously weaken the global nuclear nonproliferation regime. Still, Americans need to see how difficult it is to remain restrained when faced with North Korean taunts and provocations and when questions inevitably remain about US (or any alliance) guarantees. 


The best solution is to build a durable alliance mechanism for closer nuclear planning and exercising. This week, with President Yoon at the White House and then at the Pentagon, the United States and South Korea can elevate the extended deterrence commitment to a level in which Seoul’s voice will be heard in potential contingency responses and the command, control, and consultation over possible nuclear use.


By giving South Korea such an active role in nuclear planning, decisions on forward deployment of advanced conventional and strategic platforms, and preparedness for nuclear weapons scenarios, some will wish to portray this as a “Korea-style nuclear sharing.” A more prominent voice and role may fall just short of sharing America’s nuclear weapons, but this new process promises a pivot on the peninsula to nuclear power-sharing. South Korea will be better able to leverage America’s longstanding nuclear superiority, and the United States will be able to leverage South Korea’s mounting comprehensive power to preserve peace and shape the future regional architecture.


This NATO-like nuclear planning group should also seek to build a multilateral path that would bring Japan and Australia into a deeper, common understanding about how best to maintain deterrence and respond to various contingencies in which deterrence might fail. After all, these US allies face increasingly sophisticated threats and all developing advanced weapons systems, from undersea vessels to hypersonic missiles. But the multilateral nature of complex extended deterrence points to the second level of alliance transformation: the alliance pivot to the Indo-Pacific region.


Strengthening Partnerships Throughout the Indo-Pacific

The US-South Korean alliance needs to expand and move deeper to strengthen cooperation with Japan and other like-minded countries in the region.


The recent restoration of South Korea-Japan cooperation in information sharing and restoring preferred trading status can be a springboard for a far more comprehensive set of partnerships for South Korea and countries throughout the Indo-Pacific region.


Trilaterally, South Korea, the United States, and Japan can move from real-time information sharing regarding North Korean missiles to enhanced operational capability for greater exercising and capacity for meeting growing drone, air, and missile threats. Equally important is to expand the scope of the alliance to encompass not just military might but economic and technological leadership among Indo-Pacific countries, as well as internationally. 


Advanced technologies, such as AI and quantum computing, and new domains, such as cyber and outer space, will alter the region’s balance of power. President Yoon’s visits to the NASA Goddard Space Flight Center in Greenbelt, Maryland, and the Defense Advanced Research Projects Agency (DARPA) in Arlington, Virginia, will highlight these broadening horizons of alliance cooperation.


Bilateral cooperation in new domains should enable new forms of multilateral cooperation. Existing mechanisms provide ample opportunity for expanding such collaboration. South Korea's work with other democratic and like-minded actors must remain competitive in critical and emerging technologies, backed by a secure supply chain and a trusted data flow. 


The Quadrilateral Security Dialogue is, first and foremost, about economic and technological leadership, and South Korea should be brought in to participate in elements related to these areas. The area most ripe for addition, without joining the Quad, relates to maritime domain awareness. South Korea is advancing its aerospace and undersea capabilities. At the same time, the Quad countries are pursuing an Indo-Pacific Partnership for Maritime Domain Awareness that promises to improve situational awareness throughout the vast maritime region.


Similarly, South Korea and Japan might be added to the second pillar of the Australia-UK-US (AUKUS) defense partnership focused on advancing high technology. That advanced technology pillar focuses on Artificial Intelligence (AI), maritime domain awareness, and hypersonic missiles. Given that hypersonic missiles increasingly threaten all these allies, they must work collectively to the extent possible to ensure they retain a competitive advantage—and do not lag—in developing these fast, maneuverable, and precise conventional weapons.


In addition, the Indo-Pacific Economic Framework can forge vital agreements across all four pillars—trade, supply chains, clean energy technology, and anti-corruption—to announce progress at the APEC summit that the United States will host in San Francisco in November.


Progress in IPEF may also be a harbinger for rethinking US membership in regional multilateral trade: the Comprehensive and Progressive Trans-Pacific Partnership. If IPEF can show progress, then after the 2024 election, a US president should find a way to negotiate the United States back into a regional multilateral trading group of like-minded states. 


Shaping the International Rules-Based Order

The international level of alliance transformation should allow South Korea to realize its full potential as a “global pivotal state” and for like-minded countries to help establish the rules of the road necessary to address traditional security problems and accelerate new challenges such as climate change.  


With President Yoon set to attend his second NATO summit in Vilnius in July, South Korea has a unique potential to demonstrate that it takes the most fundamental precept of the United Nations Charter seriously: namely, the sovereign equality of nations. Unlike China’s ambassador to France, who thinks that “ex-Soviet countries do not have effective status under international law,” and unlike Russia’s leader, who thinks invading neighboring states and bombing civilian cities is a legitimate means of conducting statecraft, President Yoon has become steadfast in defense of a rules-based order.


“Seoul has already been a generous provider of humanitarian assistance to Ukrainians, a timely arms supplier to front-line NATO member state Poland, and helped the United States backfill its 155 mm ammunition so that Washington could keep Ukraine’s self-defenses strong. Of course, South Korea has the potential to make an even more substantial contribution to Ukraine’s defense against brutal and unlawful aggression, and I hope it does.


Less controversial but still very important will be to parlay growing two-way investment in semiconductor chips, electric vehicle batteries, and other advanced technologies into a more comprehensive network of like-minded high-tech nations. Harmonizing industrial policies like the Inflation Reduction Act and the CHIPS and Science Act will also require multilateral negotiation and compromise. And as suggested by the activities of the G-7 nations, including to help ensure secure access to critical minerals or the NATO nations in providing that Russian aggression against Ukraine is not allowed to prevail, security in the twenty-first century demands new forms of international cooperation.


In so doing, they must find ways to formulate a modus vivendi for providing an optimistic, forward-looking architecture in which nations retain autonomy and the ability to fend off predatory and authoritarian models of governance. Helping Ukrainians protect their sovereignty from a deadly and unlawful attack and ensuring other actors don’t resort to brute military force and coercion; creating and regulating the global digital and high-tech economy, and safeguarding a rules-based system from malign state and non-state actors; and providing real hope and prosperity to our citizens and people of goodwill throughout the world; through all these and other means, the alliance can achieve even more remarkable feats in the seven decades ahead.


Even if cooperation falls short of maximum alliance cooperation, this week’s fifth meeting of the two leaders, since President Biden visited Seoul 10 days after President Yoon’s inauguration, should validate alliance policy. President Yoon has been wise to portray South Korea as a global pivotal state, and President Biden has been shrewd in doubling down on allies and partners.


Dr. Patrick M. Cronin is the Asia-Pacific Security Chair at the Hudson Institute and Scholar in Residence at the Carnegie Mellon University. Dr. Cronin’s research analyzes salient strategic issues related to U.S. national security goals in the Indo-Pacific region and globally. His writing touches on protecting national interests and world order despite intensified great-power competition, the enduring North Korea problem, and other state and non-state challenges.

Previously, he was the Senior Director of the Asia-Pacific Security Program at the Center for a New American Security (CNAS); Senior Director of the Institute for National Strategic Studies (INSS) at the National Defense University, where he simultaneously oversaw the Center for the Study of Chinese Military Affairs; Director of Studies at the London-based International Institute for Strategic Studies (IISS); Senior Vice President and Director of Research at the Center for Strategic and International Studies (CSIS); and Director of Research at the U.S. Institute of Peace. During the George W. Bush Administration, he was confirmed by the U.S. Senate as the third-highest-ranking official at the U.S. Agency for International Development (USAID). He served as an intelligence officer in the U.S. Navy Reserve.  He has been an adjunct faculty professor at the University of Virginia, the Johns Hopkins University School of Advanced International Studies, and Georgetown University.

Dr. Cronin was previously senior advisor and senior director of the Asia-Pacific Security Program at the Center for a New American Security (CNAS), and before that, senior director of the Institute for National Strategic Studies (INSS) at the National Defense University, where he simultaneously oversaw the Center for the Study of Chinese Military Affairs.
Dr. Cronin has a rich and diverse background in Asian-Pacific security, U.S. defense, and foreign and development policy. Before leading INSS, Dr. Cronin served as the director of studies at the London-based International Institute for Strategic Studies (IISS). At IISS, he also served as editor of the Adelphi Papers and as the executive director of the Armed Conflict Database. Before joining IISS, Dr. Cronin was senior vice president and director of research at the Center for Strategic and International Studies (CSIS).
He has also been a senior analyst at the Center for Naval Analyses, a U.S. Naval Reserve intelligence officer, and an analyst with the Congressional Research Service and SRI International. He was associate editor of Strategic Review and worked as an undergraduate at the Miami Herald and the Fort Lauderdale News.
Dr. Cronin has taught at Georgetown University’s Security Studies Program, Johns Hopkins University’s Paul H. Nitze School of Advanced International Studies (SAIS), and the University of Virginia’s Woodrow Wilson Department of Government.

He read international relations at St. Antony’s College, the University of Oxford, where he received both his M.Phil. and D.Phil. degrees, and graduated with high honors from the University of Florida. He is a frequent contributor to The Straits Times (Singapore), DongA Ilbo (South Korea), and a regular member of the Defense & Aerospace Report’s “Washington Roundtable” podcast. He also writes for other leading publications and regularly conducts television and radio interviews.