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The Peninsula

History’s Long Shadow: Contradictions in the U.S. Commitment to Korea

Published March 13, 2023
Author: Clint Work
Category: South Korea

This piece is one of 12 contributions to KEI’s special project on South Korea’s nuclear armament debate that will run on The Peninsula blog over the next month. The project’s contributors include young, emerging, and mid-career voices, examining the debate from a historical, a domestic, and an international perspective. On Wednesday, March 15, KEI will host a conference featuring our various contributors’ work at our Washington, D.C. office and launch a compilation of all the pieces in a single, special KEI publication.

The intersection of the Korean peninsula and nuclear weapons goes back to the dawn of the nuclear age. Moreover, well before Pyongyang possessed nuclear weapons and the delivery systems to threaten Washington and Seoul, or the latter contemplated its own nuclear armament, the United States considered and threatened nuclear use on the peninsula.

The history surrounding the U.S. commitment to and presence in South Korea, including U.S. deployment of and threats to use nuclear weapons, is critical to understanding where the U.S.-ROK alliance finds itself today.

This history is characterized by a massive U.S. commitment to South Korea beset by inherent contradictions and profoundly complicated processes of extended deterrence and allied reassurance, made more so by inconsistent U.S. signals and South Korea’s intensely divided domestic politics in the post-Cold War era.

Tensions Within a Maximum Commitment

Soon after U.S. forces arrived on the Korean peninsula in 1945, Washington looked to withdraw. Korea was considered a strategic liability not worth the further expenditure of resources—U.S. forces left in 1949. Yet Korea’s linkage with the broader strategic tapestry of the early Cold War and the direct American role in the creation of South Korea made it symbolic of U.S. credibility writ large. When North Korea invaded, U.S. forces returned, saving South Korea from certain destruction. Throughout the Korean War and during an otherwise devastating conventional air campaign, the U.S. considered tactical battlefield use of atomic weapons and repeatedly simulated atomic bombing runs.

Dwight Eisenhower campaigned, in part, on a promise to end the war. Once in office, he hinted at the use of atomic weapons if armistice negotiations remained deadlocked. Although Soviet archives cast doubt on the claim, Eisenhower and other high-level officials said the threat helped end hostilities. However, such threats belied an inherent tension in Washington’s view of Korea: it was not important enough to further expand the war on or beyond the peninsula but too important to relinquish. This tension remains today.

To achieve a position of strength, deter future aggression, and demonstrate a maximum U.S. commitment, Washington agreed to a Mutual Defense Treaty (MDT) with and forward-deployment of U.S. forces in South Korea, and soon after began considering deploying tactical nuclear weapons. Knowing the move would violate the armistice, which restricted the number and types of weapons existing when the agreement was signed, yet also concerned about communist violations of the same, Washington announced it considered itself relieved of all corresponding obligations until such time as the military balance was restored. It first deployed U.S. tactical nuclear weapons in January 1958, and by the mid-to-late-1960s had deployed eight different types and nearly 1,000 warheads. Although not officially acknowledged, such deployments were an open secret.

The decision was driven by several factors. The Pentagon stated its “number one reason” was to prevent U.S. and ROK troops from being overrun. Deployment of tactical nuclear weapons and advanced conventional capabilities also aimed to “modernize” U.S. and ROK forces and pressure President Rhee Syngman to reduce a bloated ROK defense establishment almost entirely underwritten by U.S. assistance. Modernization was a means to hem in Rhee’s demands and set the parameters of Seoul’s military capabilities and agency. U.S. officials feared by introducing atomic-capable weapons, Rhee would demand the same for the ROK. They tried to balance between showing fidelity to South Korea’s security and enhancing its capabilities without incentivizing it to seek or independently develop such capabilities in a manner incompatible with U.S. interests. This dynamic preceded the Korean War and arrival of U.S. tactical nuclear weapons and continued thereafter.

More importantly, the decision to deploy tactical nuclear weapons to Korea was driven by a global strategy to incorporate nuclear weapons in U.S. military forces. Eisenhower’s New Look national security policy aimed to balance between maintaining the vitality of the U.S. economy, yet building sufficient strength to prosecute the Cold War. Alongside the doctrine of massive retaliation, utilizing nuclear weapons to deter aggression or fight a war was seen as the way to economize yet preserve strength. Four years after forward deployment in Europe, the concurrent deployment of theater nuclear weapons in Taiwan, Korea, and elsewhere in East Asia was part of this larger whole. Propelled by the exponential increase in nuclear stockpiles and growing importance of nuclear-capable weapons as the basis for U.S. military strength, the Korean deployment was tied to this broader techno-bureaucratic momentum.

The problem, however, was it applied a catch-all formula, which – alongside a monolithic conception of Communism – conflated distinct local threats in ways that veiled problematic contradictions beneath the surface.

Limited & Polarized Options

Forward deployment of large numbers of tactical nuclear weapons implied deterrence failure on a grand scale. Of course, signaling acceptance of such an enormous cost was itself meant to reinforce deterrence. Yet massive retaliation lacked credibility and nuance in the Korean context. It starkly limited options. The U.S. strategy of flexible response in the 1960s grew out of these critiques and grappled with the need to develop a more refined spectrum of options across strategic, tactical, and conventional levels, but it hardly solved the nuclear dilemma in Korea. In fact, it merely clarified the contradictions.

These were evident when U.S. officials considered reducing or making more flexible U.S. troop deployments. To do so would put greater attention on “the already heavy nuclear emphasis” of the U.S. posture, required prior commitment to a nuclear strategy, and earlier use of nuclear weapons in a conflict. Similar concerns, among others, later motivated opposition to President Jimmy Carter’s attempt to remove U.S. ground forces from South Korea in the late 1970s. Limited options and contradictions also were apparent amidst North Korean provocations during the “Second” Korean War. Following the 1968 Pueblo incident and 1969 EC-121 shootdown, Presidents Johnson and Nixon, respectively, considered but decided against the nuclear option.

Their deliberations revealed a polarized spectrum of U.S. options: between a minimum conventional response and maximum threat of nuclear use. To a degree, both lacked credibility. The former risked further provocations and angered Seoul, which expected a more robust response, thus potentially spurring its own effort to build greater strategic autonomy from Washington. The latter was so disproportionate it was unbelievable, politically costly, of dubious military utility, and, critically, went against the ROK’s own desire to avoid nuclear use in Korea. Moreover, in both cases, U.S. officials were dubious they had the requisite forces on the peninsula to go beyond a limited conventional response.

These events spurred significant ROK doubts about the U.S. commitment and further U.S. efforts to reduce and increase the flexibility of its forces in Korea. The latter, in turn, further increased ROK efforts to hedge against an uncertain U.S. commitment by initiating its own military modernization and clandestine nuclear weapons program in the 1970s. Among other strong countermeasures, Washington curbed the ROK nuclear program by promising to maintain troop levels and through Secretary of Defense James Schlesinger’s June 1975 public acknowledgement of the existence of U.S. nuclear weapons in Korea, the first ever by a U.S. official, and refusal to rule out first use on the peninsula. Ironically, the more Washington reduced and realigned its force posture, the more it found itself having to cast its nuclear shadow. This dynamic became even more pronounced amidst Carter’s abortive troop withdrawal policy.

In 1978, the Pentagon went from being mum regarding tactical nukes, to publicly asserting their “symbolic importance” as “visible evidence of the broader U.S. commitment and of the linkage between our deployed posture and the strategic nuclear forces.” Starting in 1979, Washington began to insert the “nuclear umbrella” into the text of the SCM’s Joint Communique; a practice maintained ever since. And, lest rhetoric be insufficient, U.S. nuclear ballistic missile submarines (SSBNs) suddenly began making dozens of port visits to South Korea from 1976 to 1981. Simultaneously, the alliance established the bilateral U.S.-ROK Combined Forces Command (CFC), which took over South Korea’s defense from the mostly unilateral, U.S.-led United Nations Command (UNC) and provided Seoul an increased operational and command and control role commensurate with its rapidly advancing capabilities.

The CFC created a far more integrated defense relationship, yet one within which the U.S. remained the first-among-not-so-equal partners. While temporarily settling nerves, none of these notable changes obviated the tension at the core of the U.S. commitment nor the polarized and limited options it had vis-à-vis a highly risk-acceptant North Korea. Furthermore, tighter alliance integration explicitly excluded consultation on the U.S. nuclear umbrella.

Yet during this same period of heightened concern by South Korea, deployments of tactical nuclear weapons were significantly reduced. A major security review of regional deployments found the security for such deployments unsatisfactory, diplomatic arrangements with allies inadequate, and the number of weapons deployed far in excess of war-planning requirements. Forward deployed tactical weapons systems were in range of North Korean artillery, opening them up for preemptive attack and increasing the need for early use in a conflict. Moreover, use of such weapons posed direct risks to alliance forces and, as South Korea urbanized, to the Korean people themselves and for neighboring countries depending on wind conditions. As a result of such scrutiny, the number of nuclear weapons in South Korea was reduced from roughly 540 in 1976 to approximately 150 nuclear artillery shells and bombs by 1985.

The truth, though, was the manifold escalatory risks posed by these weapons were there all along; and they are often cited today by opponents of their reintroduction. What changed in the mid- to late-1980s was the political and strategic context. The waning of the Cold War allowed for a shift, culminating in President George H.W. Bush’s Nuclear Security Initiative in September 1991, towards the unilateral removal of all U.S. tactical nuclear weapons from abroad, except for air bombs from a handful of NATO allies. Similar to the introduction of nuclear weapons to the Korean Peninsula, their removal largely was driven by geopolitical imperatives but also to help persuade Pyongyang to accept international inspections of its nuclear program – and because tactical nuclear weapons were no longer seen as necessary for South Korea’s defense. Nevertheless, a key condition to reassure Seoul and uphold extended deterrence was continued U.S. reaffirmation of the nuclear umbrella.

Post-Cold War Deterrence & Reassurance

Deterring North Korea once it advanced its nuclear and missile programs has been a far more complex challenge. U.S. nuclear posturing and signals have been inconsistent and, at times, highly provocative. Insofar as deterring full-scale attack against Seoul is the purpose of U.S. extended deterrence, these signals have succeeded. Yet they are legitimately threatening to Pyongyang, and, along with other factors, helped motivate its drive to build up its own deterrent capabilities. While U.S. threats have been partially effective at the upper, strategic level, they lack credibility below that threshold. During the Cold War, North Korea was perfectly willing to test the alliance in that space. Now, armed with its own nuclear deterrent, Pyongyang is more emboldened.

Critically, deterrence signals are also meant to reassure Seoul. Yet Seoul’s economic growth and enhanced capabilities – while the basis for a transformed, stronger alliance – have significantly complicated allied reassurance. Given Seoul’s improved capabilities and further reductions and realignments in U.S. forces, official alliance policy was for the U.S. to move to a supporting role and the ROK to take the lead in the combined defense. However, the process has been fitful, largely due to the stickiness of longstanding institutional arrangements and underpinning psychologies. For Washington, there is less emphasis on policing ROK capability advancements per se than making sure they fit into the alliance’s policy, deterrence strategy, and operational planning insofar as ROK capabilities have become more central to the alliance’s deterrence and warfighting equation. Yet, as a result, Seoul places even greater scrutiny on the U.S. nuclear umbrella.

South Korea’s democratization, too, while deepening alliance ties, has complicated the reassurance process. During the Cold War, alliance management was conducted with successive anti-communist ROK dictators; reassurance and decision-making were more centralized and controlled. Following democratization, public opinion and civil society became more prominent factors in alliance relations and ROK leaders with different views on the alliance and inter-Korean relations have entered the decision-making fray.

Progressive ROK administrations openly distinguish ROK sovereignty from the alliance and pursue a theory of deterrence premised on restraint. While hardly premised on disarmament, it is based upon a more compatriotic view of inter-Korean relations and seeks greater autonomy within and outside the alliance. Conservative administrations seek tighter alliance relations and operate with a theory of deterrence emphasizing preparedness to swiftly and even disproportionately retaliate against North Korean provocations or aggression. For them, relations with North Korea, while not without a compatriotic element, are framed more around the battle over inter-Korean legitimacy; the sameness of the people intensifies the conflict. Reassurance gets tangled as different administrations react differently to U.S. extended deterrence policy – which is itself inconsistent – and adopt ever-shifting policy trajectories.

For progressive administrations, U.S. extended deterrence measures are often seen as too much, increasing rather than lowering tensions and undermining trust building with North Korea. This results in efforts to restrain Washington and remove the “nuclear umbrella” from alliance documents and joint statements as well as disputes surrounding Seoul’s push to take a larger role in the alliance’s operational plans and command architecture. U.S. officials often view this process as overly politicized, which undermines trust and results in U.S. restraints, real and perceived, on ROK autonomy. Conservative administrations, for their part, frequently see U.S. deterrence measures as not enough. Like progressives, they seek greater input in and awareness about alliance and U.S. planning, but for different reasons. Rather than necessarily seeking a leading or autonomous role in the alliance, they want to assume a more robust ROK defense and retaliatory posture vis-à-vis North Korean provocations but also want to know the United States stands alongside them. Therefore, they also bristle at U.S. constraints.

These complex dynamics have played out in alliance consultative mechanisms over the last two decades; mechanisms which only began to actively consider alliance policy and planning around extended deterrence starting in 2010. These mechanisms represent a genuine effort to develop a more holistic approach to deter an evolving North Korean threat; to proactively fill the gap between the longstanding polarized spectrum of options; and signal to Pyongyang it cannot use its own nuclear shadow to coerce or freely operate in that gap. However, due to the aforementioned dynamics, the allies have brought different understandings to these consultative mechanisms. There appears policy consensus but beneath the surface there are perceptual and operational gaps.


If polarized deterrence options and having the requisite force posture in place on the peninsula was a problem for the U.S. and the alliance during the Cold War, it is even more so today. Pyongyang has the capability to turn the entire peninsula into an Anti-Access/Area-Denial (A2/AD) environment while threatening the continental Unites States. Moreover, in a context of great power competition, U.S. attention and resources are being pulled elsewhere, currently to Europe and potentially to Taiwan. Both factors severely restrict what assets the U.S. can bring to bear in Korea and how quickly it might do so and place greater stress on the ROK, which already bears the overwhelming conventional deterrence and defense burden.

Tightening alliance cooperation along the conventional-nuclear threshold is critical to enhancing reassurance and reducing the appeal for Seoul of its own nuclear deterrent but also signaling to Pyongyang its advancing capabilities do not afford it the luxury to coerce beneath or up to the nuclear-level. Recognizing this, both the Biden and Yoon administrations have redoubled efforts to tighten cooperation where U.S. capabilities end, ROK capabilities begin, and, most importantly, where they intertwine. To be effective, this demands Washington show greater fidelity to Seoul’s need for more information and involvement in U.S. nuclear policy and planning, beyond what historically it has been comfortable with, and for Seoul to understand the limits of such cooperation do not reflect a lack of U.S. commitment.

Clint Work is a Fellow and Director of Academic Affairs at the Korea Economic Institute of America. The views expressed here are the author’s alone.

Photo from U.S. Indo-Pacific Command’s photostream on flickr Creative Commons.

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