What’s in a Tripwire: The Post-Cold War Transformation of the US Military Presence in Korea

Executive Summary

From the moment U.S. troops first arrived on the Korean Peninsula, U.S. policymakers have sought to reduce the U.S. military presence and pass the defense burden back to the Republic of Korea (ROK, or South Korea). Yet, in each instance when a U.S. president attempted to reduce, realign or withdraw these U.S. forces, the policy has been delayed, truncated, or canceled, followed by promises to keep force levels constant at arbitrary top-line levels. Successive U.S. presidents have been unable to militarily disengage from the Korean Peninsula due to apprehension about undermining deterrence against a growing North Korean threat and, more importantly, broader U.S. strategic imperatives. Over the years, the fitful evolution of the U.S. force presence has driven contradictory policy dynamics within the US-ROK alliance.

These contradictions have become more acute following the end of the Cold War. Within a democratic South Korea, alliance management has become more challenging, being intertwined with highly politicized debates about ROK dependence versus autonomy, with lingering uncertainty about U.S. staying power, and often complaints about U.S. heavy-handedness. Moreover, South Korea’s economic and defense modernization, alongside the gradual reduction and realignment of U.S. forces, has resulted in a division of labor of sorts, with Seoul taking on the lion’s share of responsibility for conventional deterrence and defense on the Korean Peninsula and the U.S. providing extended deterrence for South Korea against North Korea’s growing nuclear capabilities.

However, North Korea’s advancements in long-range missile and nuclear weapon capabilities — specifically its potential ability to strike the continental United States with a nuclear-armed intercontinental ballistic missile (ICBM) — raises pressing questions about whether Washington would risk Seattle to save Seoul. The more responsibility Seoul takes on, the greater scrutiny is directed on Washington’s extended deterrence commitment.

In recent years, U.S. and ROK officials have reframed the relationship as a comprehensive strategic alliance, which nests its traditional military and security components in an expansive array of shared democratic values, economic ties, and mutual support for a rules-based international order. However, such discourse also papers over very real differences at the core of the alliance. The proliferation of consultative mechanisms over the last decade, which were meant, in part, to address these differences, have not adequately done so. Instead, North Korea’s steady nuclear and missile advancements and burgeoning great power competition between the United States and China and Russia pose new challenges to alliance cohesion. While the U.S. and ROK continue to reiterate the “ironclad” nature of relations, South Korea has expressed growing doubts about the credibility of U.S. extended deterrence and increasing support for building its own nuclear deterrent.

Moving forward, alliance managers must honestly address these differences. The United States should upgrade the relationship with South Korea to the level of other alliances in the region, give it more consistent bandwidth — not only when crisis requires it — and provide greater clarity within alliance consultative mechanisms about the U.S. nuclear umbrella. Washington should also continue to encourage Seoul to expand its role in the region and improve ties with Tokyo but also show sensitivity toward Seoul’s unique geopolitical vulnerability and perspective. South Korea, while rightly seeking reassurance and clarity and a greater voice in the implementation of the U.S. extended deterrence commitment, should also better understand the limits of such consultations, including the U.S. president’s sole authority in authorizing the use of nuclear weapons. South Korea should strive to take more of a lead in the alliance while accepting it will never achieve full autonomy or self-reliance as long as the alliance exists, and U.S. forces are stationed on the peninsula.

Introduction

The presence of the U.S. military has been fundamental to the Republic of Korea’s national security for nearly its entire existence. The only period when U.S. combat forces were not on South Korean soil was from June 1949 until the outbreak of the Korean War in 1950. The shock of the war deeply ingrained the importance of having a U.S. presence in South Korea into the minds of ROK and U.S. policymakers both to help ensure stability on the Korean Peninsula and support U.S. strategic imperatives beyond it. The persistence and growth of the North Korean threat since the war have made U.S. efforts to adjust its presence in South Korea all the more complicated. At the same time, there has long been significant skepticism within the United States about the value of maintaining troops in South Korea, as well as a strong desire to gradually disengage.

This skepticism has compelled multiple presidents, Republican and Democrat alike, to implement changes in the structure and posture of the military force to make it more enduring. Driven by broader strategic shifts, such as the Nixon Doctrine, post-Vietnam withdrawals, the end of the Cold War, the Global War on Terror, and persistent calls to shift the defense burden to an increasingly capable and wealthy ROK ally, Washington has sought to gradually replace itself by passing the bulk of the deterrence and defense commitment onto Seoul.

However, the U.S. could never fully remove itself from the ROK. In each case, when a U.S. president reduced, realigned, or tried to withdraw U.S. forces, they have navigated deep-seated concerns about sparking instability or war on the peninsula. They have also risked more important strategic objectives, namely, Japan’s security, regional stability and prosperity, and another power establishing exclusive hegemony over the region.

In the post-Cold War period, the evolution of the U.S. force presence in South Korea has been erratic. When U.S. forces are reduced and realigned, it results in a more productive division of labor and a more mature alliance. Yet, for the reasons mentioned above, such changes are often curtailed, delayed, or ultimately called off. This, in turn, results in a return to the status quo, promises to keep troop levels constant, and policy drift. The uneven nature of these changes causes discordant responses in Seoul, including the incessant concern about the credibility of Washington’s extended deterrence commitment, which incentivizes Seoul to adopt a more independent and self-reliant security posture. Meanwhile, the U.S. wavers between encouraging, even pushing the ROK to do more, and yet tries to restrain South Korea from being too independent, resulting in friction and mistrust between the two allies.

In recent years, U.S. and ROK leaders and alliance managers have worked to craft a comprehensive strategic alliance, nesting its traditional military and security components in an expansive array of shared democratic values, economic ties, and mutual support for a rules-based international order. Although the effort to broaden and deepen the alliance has strengthened it, it has also veiled a very real and potentially fractious lack of cohesion at the heart of the relationship. Better understanding the post-Cold War evolution of the U.S. force presence and the frictions it has caused is essential to steadily navigate future alliance transformation.

Historical Backdrop

Korean War as Catalyst

In some respects, the U.S. has been trying to leave the ROK ever since it arrived. Throughout the 1945-1948 U.S. military occupation period in the southern part of the Korean Peninsula, during which South Korea was created as a sovereign state, the U.S. sought to militarily disengage itself. Amid wider post-WWII demobilization and resurgent domestic priorities, U.S. policymakers concentrated on other more important foreign policy interests. South Korea was not one of them, as U.S. strategists saw it as a strategic liability. By 1948, official U.S. policy aimed to withdraw from the ROK with “the minimum” of negative effects. Although there were some contrarian voices within the U.S. government (USG) that highlighted the link between South Korea and Japan’s security and regional stability — they were a minority. The consensus was that South Korea lacked intrinsic value. The last U.S. combat forces departed in June 1949, leaving a skeletal group of military advisors backed by uncertain signals about the degree of U.S. commitment.¹  Note: The most often cited example is Dean Acheson’s January 12, 1950 remarks at the National Press Club, which declared a consolidated security perimeter for Asia that excluded South Korea and Taiwan from areas of vital U.S. interest. However, General Douglas MacArthur had described the defense perimeter in very similar terms in March 1949. See: Samuel F. Wells Jr., Fearing the Worst: How Korea Transformed the Cold War (New York: Columbia University Press, 2020), 21, 58-59.  

The outbreak of the Korean War a year later was a critical juncture in more ways than one. First, before the war, U.S. policymakers assumed they could separate the political from the military elements of the United States’ commitment. The war proved otherwise and transformed the U.S. commitment from a minimum to a maximum one constituted by a formal alliance, a mutual defense treaty (MDT), and a forward-deployed U.S. force presence. Subsequently, the political commitment embodied in the MDT and U.S. military were inextricably linked. The latter underpinned the credibility of the former as U.S. forces gave the treaty meaning, and without their presence, the treaty was meaningless.

Second, viewed by key policymakers through a broader Cold War prism, the outbreak of the war catalyzed an exponential increase in U.S. defense budgets and the creation of a national security state in the U.S., and the solidification of a global military basing and alliance system abroad.²  Note: Wells Jr., Fearing the Worst; see also: Robert Jervis, “The Impact of the Korean War on the Cold War,” The Journal of Conflict Resolution 24, no. 4 (December 1980): 563-592.    The war provided the necessary motivation for the States to overcome its domestic political obstacles and resolve bureaucratic infighting in order to establish a new policy of globalized national security embodied in NSC-68, based on U.S. military primacy and “the rapid building up of the political, economic, and military strength of the free world.” Thus, the war not only inextricably linked the political and military components of U.S. commitment to South Korea, but also the presence of U.S. forces on the peninsula with wider U.S. regional and strategic imperatives.

Even so, the war did not change the fundamental push and pull at the heart of the United States’ commitment. Before entering office in 1953, Dwight Eisenhower pledged to bring the inconclusive conflict to an end. Six months later, the Eisenhower administration signed the Korean War Armistice Agreement, ceasing all hostilities without achieving peace. Eisenhower firmly decided against continuing the war on the peninsula or expanding beyond it. However, he also decided against a complete U.S. troop withdrawal. The Korean commitment was viewed as not being worth expending further blood and resources or touching off a global conflagration with the Soviet Union, but it was too important simply to relinquish. President Eisenhower stated that U.S. forces would gradually redeploy from the peninsula as conditions warranted.

Nixon and Carter: Loosening the Tripwire

However, conditions did not allow for redeployment for nearly two decades. Except for the initial postwar reduction of U.S. forces from a wartime high of 392,483 in 1953 to around 75,000 troops by 1956, they hovered between 70,000 and 50,000 for the next fifteen years. The bulk of the force was the U.S. I Corps, otherwise known as the “Shield of Seoul,” consisting of two army divisions, with one defending the 18.5-mile frontline west-central sector of the Demilitarized Zone (DMZ) and the other in reserve between Seoul and the DMZ.³  Note: Kwang Sub Kwak, “The United States-ROK Alliance, 1953 — 2004: Alliance Institutionalization” (Ph.D. dissertation, Southern Illinois University at Carbondale, 2006), 66-90.    Together, they blocked two main invasion corridors used during the war. U.S. forces served as a tripwire in case of another invasion, which would spark immediate U.S. involvement due to the expectation of significant loss of life. However, by the late 1960s, conditions had changed, and Washington moved to loosen the tripwire.⁴  Note: As stated in my previous work, initially, the meaning of the tripwire was quite literal: minimal U.S. ground troops on the frontline whose presence guaranteed immediate U.S. involvement in another Korean conflict. These forward-deployed ground troops were militarily necessary to slow down advancing North Korean forces to allow time for contiguous U.S. (CONUS)-based reinforcements to arrive; they were also a credible physical manifestation of the U.S. commitment to South Korean security embodied in the US-ROK Mutual Defense Treaty (MDT). No president or Congress would stand idly by as tens of thousands of U.S. military and civilian personnel were killed in the early stages of a conflict.  

The early success of Seoul’s export-oriented industrialization and its military’s combat experience in the Vietnam War and against North Korean provocations during the “Second Korean War” (1966-1969) enabled the U.S. to pull back. Also, such provocations — notably the Blue House Raid and Pueblo Incident in 1968 and the 1969 EC-121 spy plane shootdown — alerted U.S. policymakers to the danger of sudden escalation and limitations of a U.S. force posture posed for tactical flexibility in response to the Democratic People’s Republic of Korea’s (DPRK) provocations. Coinciding with the metastasizing costs of the war in Vietnam, President Richard Nixon entered office, calling for a wider strategic shift.

In the context of the Nixon Doctrine, this included picking up where the Johnson administration had left off and devising the first major post-Korean War reduction and realignment of troops in South Korea. To be clear, the Nixon Doctrine was less about disengagement than it was restructuring the U.S. presence in the ROK to better rationalize staying put while also passing more of the burden onto South Korea. This required U.S. policymakers to adjudicate the potential instabilities and mixed signals of loosening the tripwire.

In 1971, under the rubric of the “Koreanization” of the ROK’s defense, the Nixon administration withdrew the U.S. 7th Infantry Division (7ID) and pulled back the frontline 2nd Infantry Division (2ID) to the Forward Edge of Battle (FEBA) line. Doing so left all frontline defense to the ROK. Initially, the plan involved removing 2ID while keeping 7ID in reserve. However, due to U.S. and ROK concerns about the destabilizing effect of withdrawing the more forward-deployed of the two U.S. divisions, the plan was flipped.⁵  Note: U.S. Congress, House, Committee on International Relations, Investigation of Korean-American Relations: Report of the Subcommittee on International Organizations, 95th Cong., 2d sess., 1978, H. Rep., 61. (also known as the “Fraser Report”), 63, footnote 56.    Despite internal U.S. plans for further reductions, intense opposition from the ROK, a breakdown in inter-Korean talks and increasing evidence of a North Korean military buildup, international crises elsewhere, and the Watergate scandal leading to Nixon’s resignation, these plans never went forward.

In the wake of the U.S. withdrawing from Southeast Asia, President Gerald Ford issued his Pacific Doctrine, closing the loop on Nixon’s. At that point, U.S. forces in Korea took on increased strategic and political symbolism as the last remaining deployment on the East Asian mainland. Furthermore, as Henry Kissinger noted: “the reason for America’s continued commitment was simple and the same in South Korea and Europe: we doubted the ability of our allies to assume their own defense completely and we feared that the removal of our shield might tempt aggression.”⁶  Note: Henry Kissinger, The White House Years: Vol. II: Years of Upheaval (Boston: Little, Brown, 1982), 308.     Also, as declassified materials show, U.S. officials feared what Seoul’s independent efforts might produce: namely, overly-offensive and escalatory missile strike capabilities or an indigenous nuclear weapons program, which Washington either deliberately hemmed in or shut down. President Ford’s view after Vietnam was that the U.S. could not pull back any further. However, his successor, Jimmy Carter, felt it had not pulled back enough.

President Carter entered office intent to withdraw all remaining U.S. ground combat forces from the Korean Peninsula. Partly motivated by the premises behind Nixon’s reductions of more tactical flexibility and allied burden sharing, Carter was also inspired by the shadow of Vietnam and repulsed by ROK leader Park Chung-hee’s military authoritarianism and human rights abuses. He saw no reason the U.S. should get caught up in another quagmire in Asia in defense of a disreputable, undemocratic ally. However, by July 1979, his policy was put in “abeyance,” which was code for cancelation.

On paper, his policy was an operationally viable plan, consisting of the gradual three-phase withdrawal of 2ID’s three combat brigades and supporting troops. It required massive military assistance and material transfers to Seoul and would leave the bulk of the combat forces in place until the final phase sometime in 1982, which would, theoretically, be Carter’s second term. If fully implemented, the plan would have removed roughly 26,000 troops, leaving 12,000-15,000 in place. These would have consisted of the U.S. Air Force and intelligence, along with logistics, command and control elements mostly stationed south of Seoul. If Nixon had loosened the tripwire, Carter’s plan appeared to remove it entirely.⁷  Note: Clint Work, “A Fly in Amber: Carter’s Korea Troop Withdrawal & The Recasting of U.S. Hegemony and Korean Agency” (Ph.D. dissertation, University of Washington, Seattle, 2019).   

Yet, legislative opposition to passing the necessary military aid package delayed the plan. This was due to the Koreagate scandal and general resistance to withdrawal. It was then shut down entirely due to new intelligence showing North Korea’s forces were larger, more heavily armored, and forward-deployed than previously thought. Moreover, those in the interagency process who crafted the withdrawal plan were also its biggest opponents. They structured it in such a manner so the variables above would stall the process and provide time to reconsider. Even without the new intel on North Korea, one of them said, they would have found a way to defeat the policy.⁸  Note: Ibid, 431.  

Carter’s policy also fell prey to the onset of the Second Cold War, a series of rolling international crises, and a New Right political movement domestically. All of these events cast Carter’s foreign policy, including the Korea withdrawal, as indecisive and weak. Riding the conservative wave, Ronald Reagan handily defeated Carter in the 1980 election, and one of his first acts in office was to embrace Seoul’s newly minted authoritarian leader, Chun Doo-hwan, at the White House and officially put to rest any further talk of troop withdrawal. During Reagan’s administration, he increased U.S. forces in Korea by several thousand.

Post-Cold War Reshuffling

Congressional Pressure and Bureaucratic Initiative

When President George H.W. Bush entered office in January 1989, things had changed. While Bush told ROK President Roh Tae-woo in February that his Korea policy would essentially be the same as Reagan’s, trends said otherwise. With Cold War tensions waning and domestic economic concerns rising, the containment ethos could no longer veil the real political-economic differences between the U.S. and its allies. Although Japan bashing occupied the front pages, criticisms of South Korea and calls for it to taken on a greater share of the burden were a close second. South Korea’s young and highly contentious democracy was bubbling with protest and more open displays of anti-American sentiment than ever before. Many in Congress and the American public began to wonder why a U.S. force presence should provide protection for wealthy allies who simultaneously refused our U.S. goods and whose publics protested — sometimes violently — that same presence.

In this context, with lawmakers wanting to withdraw U.S. troops driven by budgetary rather than strategic rationales, Carl Ford, the deputy assistant secretary of defense for East Asia, took the initiative to do so. Given the go-ahead by Secretary of Defense Dick Cheney, Ford drew up a draft strategic initiative for East Asia and worked with key contacts on the Senate Armed Services Committee (SASC) — particularly in Senators Nunn, McCain, and Warner’s offices — to craft legislation that channeled, yet simultaneously buttressed, congressional pressure and permitted the executive branch to frame the overall process of reducing and restructuring the U.S. presence in South Korean and the region. With only minor changes, Ford’s draft made its way into the Nunn-Warner amendment, requiring the executive branch to report to Congress on its plans for phased force reductions.⁹  Note: Carl Ford, interview by the author, June 4, 2021; see also: Michael J. Green, By More Than Providence: Grand Strategy and American Power in the Asia Pacific Since 1783 (New York: Columbia University Press, 2019), 445, footnote 92.     

The Nunn-Warner amendment superseded other resolutions calling for more immediate and larger reductions. It was passed as part of the annual defense authorization process and signed by Bush, thus becoming a presidential directive. The first East Asian Strategic Initiative (EASI) report was submitted to Congress in April 1990, followed by a second updated version in the spring of 1992.

Implementing the East Asian Strategic Initiative (EASI)

EASI presented a 10-year, three-phase plan for the reduction and restructuring of the U.S. forces in the region and the rearrangement of allied relationships, with an emphasis on Korea, Japan, and the Philippines. Phase I (one to three years) aimed for a 10-12 percent (or 14,000-15,000) reduction in the 135,000 forward-deployed forces in the Pacific. Regarding South Korea, this consisted of a modest force reduction of about 7,000 personnel — 2,000 Air Force and 5,000 ground forces — and promised to support steady improvements in South Korea’s defense capabilities.

Phase II (three to five years) would follow a reexamination of the North Korean threat and an evaluation of the progress and the effects of Phase I. Depending upon the state of inter-Korean relations and improvements in ROK military capabilities, the U.S. would possibly restructure and reduce 2ID by 6,500 troops. Upon the successful completion of Phases I and II, in Phase III (five-10 years), fewer U.S. forces would be required to maintain deterrence in South Korea, and the ROK “should be ready to take the lead role in their own defense.” Although the EASI reports established a clear overall vision, specific numbers for Phase III were not provided. Furthermore, the reports were deliberately structured in a gradual manner in order to temper and, if necessary, check their implementation.

Carter’s earlier withdrawal policy informed Ford and his counterparts’ approach. Although they opposed Carter before, they understood times had changed, and force adjustments were necessary. Deliberate cooperation between the executive and legislative branches, which sorely lacked under Carter, was necessary to craft a viable plan. Furthermore, a longer and more gradual timeline was essential for allied buy-in and to allow for reconsideration if conditions changed. Lastly, at the core of EASI was an emphasis on proper capabilities, as determined by commanders in the field, rather than arbitrary troop numbers. In the short term, some force reductions were expected. In the long term, however, it could mean either reducing or surging forces as conditions required. The result was a better-rationalized force presence that was meant to endure well beyond the Cold War.¹⁰  Note: Carl Ford, interview by the author, June 4, 2021.  

Between the 1990 and 1992 EASI reports, the dizzying and transformative course of global events, such as German reunification, the dissolution of the Warsaw Pact, the signing of the Strategic Arms Reduction Treaty (START), and, above all, the collapse of the Soviet Union, justified U.S. force reductions abroad and a burgeoning desire in Congress to cash in on the peace dividend. Yet this applied more to Europe than Asia, where Cold War divisions remained alive and well in areas like the DMZ and the Taiwan Strait.

Seoul’s normalization of relations with Moscow in 1990 and Beijing in 1992; North and South Korea’s entry into the United Nations in 1991; and, soon thereafter, the signing of the Inter-Korean Agreement on Reconciliation, Nonaggression and Exchanges and Cooperation, as well as the Joint Declaration of South and North Korea on the Denuclearization of the Korean Peninsula, signaled a marked reduction of tensions on and around the Korean Peninsula. So, too, did the removal of all U.S. tactical nuclear weapons from South Korea in the fall of 1991, which enabled the Joint Declaration to be made between Seoul and Pyongyang.

However, the inter-Korean agreements, though historic, remained aspirational in large part due to growing concern about North Korea’s nuclear program. In November 1991, Secretary of Defense Cheney postponed EASI’s Phase II troop reductions in Korea “until the dangers and uncertainties surrounding the North Korean nuclear weapons program have been thoroughly addressed.” President Bush upheld that decision during a January 1992 visit to Seoul, during which he also praised the recent inter-Korean pacts yet warned: “paper promises won’t keep the peace.”

The 1992 EASI report reaffirmed the administration’s stance. Completed by December 1992, Phase I reductions included 1,987 Air Force personnel and 5,000 troops that made up 2ID’s 3rd Brigade. The 3rd Brigade, which was previously slated for withdrawal under President Carter’s troop withdrawal policy, oversaw the western corridor between Munsan and Paju, north of Seoul, and was replaced by ROK forces. The total number of U.S. forces stood at around 37,000 at the end of Bush’s term in office, roughly where they had when Carter left.¹¹  Note: Kwak, “The United States-ROK Alliance, 1953 — 2004,” 90.  

Other factors induced caution in adjusting the presence of U.S. forces in the ROK. Although EASI had forecast force reductions in the Philippines, it had not foreseen the sudden withdrawal of all U.S. forces from the country. When that occurred, it highlighted the need for judiciousness in South Korea and elsewhere in the region. In this context, EASI stressed the critical regional role of U.S. forces in South Korea and Japan.

From Global Containment to (Re)emergence of Regional Imperatives

During the Cold War, the U.S. security presence in the region was primarily seen through the global containment aspect of U.S. strategy vis-à-vis the Soviet Union, which masked the important role U.S. forces played in addressing the multiplicity of security concerns throughout the region that differed from country to country and within the subregions of the Pacific area. However, EASI stated that the regional roles of U.S. forces were the more “traditional aspect” of the U.S. military presence, preceding the Cold War itself. When the Cold War ended, these regional roles once again assumed “primary importance in our security engagement in the Pacific theater.” Those forces were also essential to the United States’ ability to meet contingencies in adjacent regions like the Persian Gulf or Southwest Asia.

EASI’s intertwined logics were reinforced by the Bush administration’s broader national security and national defense strategies, including its Base Force concept. These strategies recognized the tectonic shift of the end of the Cold War while maintaining that the first line of U.S. defense was abroad. The uncertainty of the era was reason in and of itself to maintain robust, albeit more flexible, global force deployments as a bulwark against instability or security vacuums.

Furthermore, while great power threats may have receded for the moment, regional ones remained. For defense planners, the two most salient were Iraq and North Korea. Operation Desert Storm proved the first, and Pyongyang’s nuclear ambitions the second. Furthermore, whether in the form of Russian revanchism or the future rise of another great power, U.S. forces were critical to preserving American preponderance. Nonetheless, many criticized what they saw as the Pentagon’s invention or inflation of threats to justify a self-fulfilling force presence. In 1992, Congress was just as boisterous as in previous years over allied cost sharing and the need to focus on the economy. Candidates in the Democratic primary, as well as Bush’s Republican primary opponent, Pat Buchanan, harped on these themes throughout the 1992 campaign, calling for defense budget cuts.

Les Aspin, chairman of the House Armed Services Committee, was outspoken on these issues. As President Bill Clinton’s first secretary of defense, he established the Bottom-Up Review (BUR), which was motivated by the same premises as the Bush administration’s Base Force concept, to examine how to adapt U.S. defense strategy and force posture to the new strategic environment by reducing defense expenditures, shrinking the overall force and the proportion of troops stationed abroad, while seeking to reduce forces even more. Nevertheless, BUR was ultimately grounded in the same unyielding idea that the U.S. had to maintain a significant forward presence to deter aggression and preserve regional stability.

The Nye Initiative Closes the Loop on EASI

When it came to Korea, Clinton inherited a worsening relationship with Pyongyang, which quickly turned into a rolling crisis and near war in 1994. Although war was averted, and the U.S. and North Korea signed the 1994 Agreed Framework, further U.S. troop reductions in South Korea were out of the question, given the climate at that time.

Even so, Clinton administration officials began to observe a worrisome malaise among allies in the region regarding the credibility of the U.S. commitment, largely caused by the administration’s own mixed signals. Consequently, Joseph S. Nye Jr., the assistant secretary of defense for international security affairs, and others spearheaded the February 1995 release of the United States Security Strategy for the East Asia-Pacific Region (otherwise known as the Nye Initiative). If Ford’s Pacific Doctrine closed the loop on the Nixon Doctrine in the mid-1970s, the Nye initiative did the same thing in relation to EASI. The Nye Initiative reaffirmed no further reductions would occur, and the U.S. would maintain 100,000 military personnel throughout the region until at least the end of the 20th century.

However, EASI and the Nye Initiative shared certain core assumptions. Both highlighted the increasing importance of the region to U.S. trade, economic, and foreign policy interests and the importance of keeping forward-deployed U.S. forces for regional stability. The Nye Initiative highlighted these factors, along with concerns about unpredictable North Korean and Chinese intentions, as reasons to stay put. EASI, on the other hand, highlighted them as caveats and potential reasons to shut down force reductions during each of its three phases. The George H.W. Bush administration had already pointed to North Korea in order to postpone further reductions.

The key differences between EASI and the Nye Initiative were their respective audiences and shift in focus. EASI had a domestic audience, telling Congress the U.S. would pull back this far, whereas the Nye Initiative told allies and adversaries that the U.S. would not pull back any more than this.¹²  Note: Yoichi Funabashi, Alliance Adrift (New York: Council on Foreign Relations Press, 1999), 249.    Furthermore, EASI explored alterations in the number and structure of U.S. forces in the region and South Korea based on the recommendations and threat assessments of field commanders. The Nye Initiative, however, shifted focus back to affirming arbitrary force numbers again. In this respect, it was more of a policy statement than a strategy.¹³  Note: Carl Ford, interview by the author, June 4, 2021  

The key point is that the Nye Initiative’s primary focus was not on South Korea but on other, more important priorities, including reaffirmation of the US-Japan alliance and engagement with China. The former, which was Washington’s most important alliance relationship in the region, was seen by both U.S. and Japanese officials as being off course and in need of redefinition. Regarding its relationship with Beijing, Washington aimed to encourage its entry into the US-led international order while balancing the military risks of its continued rise.¹⁴  Note: Joseph S. Nye Jr., interview by the author, December 23, 2021.    Although there was some discussion with ROK officials and in the U.S. interagency process about engaging in similar dialogue strengthening and alliance redefining efforts with South Korea, the U.S. State Department was cautious about doing so, and some felt the ROK itself was not ready to go that far.¹⁵  Note: Michael Finnegan, interview by the author, June 10, 2021; see also, Funabashi, Alliance Adrift, 273.  

The Future of the Alliance, Stunted

Rumsfeld Reviews Postures and Transforms Alliance

For the remainder of the 1990s and in the early 2000s, alliance relations with South Korea took a back seat. The Agreed Framework muddled along while concerns mounted regarding Pyongyang’s advancing ballistic missile program. South Korea navigated its democratic consolidation alongside the East Asian financial crisis, which nearly brought the ROK economy to its knees. Most notably, South Korea’s first progressive president, Kim Dae-jung, initiated his Sunshine Policy, increasing engagement with Pyongyang and leading to the historic June 2000 Inter-Korean Summit with DPRK leader Kim Jong Il. This summit was a paradigm-shifting event between the two Koreas and Seoul and Washington, where the U.S. was directly engaged throughout. However, there was no deliberate effort during this period to upgrade the alliance for the 21st century.

That changed starting in 2002 when two South Korean girls were tragically killed by a U.S. armored vehicle driving on a public highway. When the U.S. service members involved were not convicted for their deaths, intense protests broke out, with some South Koreans calling for the immediate withdrawal of U.S. forces. This all occurred in the run-up to the 2002 ROK presidential election, helping propel Roh Moo-hyun, an unorthodox, populist, and progressive leader, to victory. President-elect Roh criticized past ROK political and military leaders for their dependence on the U.S. and openly called for a more equal US-ROK alliance. Seoul, he argued, needed to become more self-reliant and independent.¹⁶  Note: Yoichi Funabashi, The Peninsula Question: A Chronicle of the Second Korean Nuclear Crisis (Washington DC: Brookings Institution Press, 2007), 230-261.  

Secretary of Defense Donald Rumsfeld and officials within the Office of the Secretary of Defense (OSD) saw an opportunity. When Rumsfeld took the reins at the Pentagon in 2001, he was intent on restructuring static forward deployments, like the U.S. presence in South Korea. The 9/11 terrorist attacks added further impetus for a more flexible and expeditionary military that would be less tied to any one location and more able to confront state and nonstate threats alike. Changing the force structure and posture in South Korea would propel Rumsfeld’s broader Global Posture Review and, at the same time, transform the US-ROK alliance. President-elect Roh’s own rhetoric and policy platform would help achieve that goal.

Even before Roh was elected, U.S. defense officials had secured the ROK’s agreement to begin the Future of the Alliance (FOTA) policy initiative in order to reassess and strengthen the alliance. Within months of Roh’s inauguration, alliance managers hit the ground running. During FOTA talks, and later the Strategic Policy Initiative (SPI), officials in the Roh and Bush administrations navigated a complex set of inter-related issues. These included the following: the realignment and reduction of U.S. forces in Korea, key mission transfers from the U.S. to the ROK, the strategic flexibility of U.S. forces in Korea, and the transition of wartime operational control (OPCON) from the U.S. to the ROK.¹⁷  Note: Richard Lawless, interview by the author, October 23, 2021; and Michael Finnegan, interview by the author, June 10, 2021.  

Implementing the Future of the Alliance (FOTA) and Strategic Policy Initiatives (SPI)

Picking up agreements previously shelved in the early 1990s, alliance managers renegotiated the Land Partnership Plan (LPP) and Yongsan Relocation Plan (YRP). Under these plans, U.S. forces north of Seoul were first to be consolidated, while dozens of other U.S. bases were closed and transferred back to the ROK. Next, forces north of the capital, including the roughly 15,000-person 2ID, along with most U.S. personnel stationed at Yongsan Garrison in central Seoul, were to be realigned further south. They would then eventually be repositioned at regional hubs, most notably Camp Humphreys and Osan Air Base in the city of Pyeongtaek, about 40 miles south of Seoul. In the summer of 2004, after a year of hushed internal discussions with their ROK counterparts, the U.S. officially announced plans to reduce its 37,000 troops by 12,500 by the end of 2005. The reductions included the redeployment of 2ID’s 3,600-strong 2nd Infantry Brigade to the war in Iraq and about 9,000 additional support and administrative personnel. Due to vociferous opposition from Seoul, Washington agreed to push the date back and phase out the reductions by the end of 2008.

Internal U.S. planning also envisioned the eventual redeployment of 2ID’s final ground maneuver unit, the 1st Armored Brigade Combat Team (ACBT), which meant all U.S. ground combat forces would be removed from Korea for the first time since the Korean War.¹⁸  Note: U.S. Military Official, interviewed by author, March 3, 2022.    If completed, force reductions and realignments would have translated into an air- and naval-centric U.S. force structure that would be postured south of Seoul. This was, in essence, what Carter’s plan had conceptualized three decades prior. The outcome of the process, which also included significant air, firepower, missile defense, and Command, Control, Communications, Computers, Intelligence, Surveillance, and Reconnaissance (C4ISR) upgrades to remaining U.S. forces, would have enhanced the tactical mobility of U.S. forces, shifted the focus to maintaining specific capabilities rather than an arbitrary troop number, and refined the alliance’s division of labor by passing the overwhelming bulk of conventional defense to the ROK in a manner that was commensurate with its growing capabilities.

Strategic Flexibility: Agreement to Disagree

Reduction and realignment were not only geared to upgrade the alliance, but to also enhance the strategic flexibility of U.S. forces stationed in Korea, freeing them up to be used in other contingencies or crises off the peninsula. Secretary Rumsfeld, like others before him, argued the U.S. could not have one command devoted solely to the defense of a single ally.¹⁹  Note: Richard Lawless, interview by the author, October 23, 2021; Michael Finnegan, interview by the author, June 10, 2021.    Nevertheless, the issue was a nonstarter for Seoul. As such, alliance bureaucratic logrolling ensued.

In 2006, Washington and Seoul officially confirmed their mutual understanding of the rationale and necessity for strategic flexibility and that the ROK would not be involved in a regional conflict in Northeast Asia against its will (i.e., meaning a US-China shootout in the Taiwan Strait), but that was as far as the alliance managers got. Simply put, they agreed to disagree, and after 2006 any mention of strategic flexibility faded from formal alliance statements. While disagreement on strategic flexibility resulted from core geopolitical differences, it was also driven by complications in the force reduction and realignment process itself.

Roadblocks to Force Reduction and Realignment

The reduction and realignment of U.S. forces south of Seoul quickly became mired in South Korea’s domestic politics. ROK conservatives argued U.S. plans were a step toward full withdrawal and possible abandonment. Some blamed the Roh administration, which, they argued, was trying to end the alliance. Progressive in South Korea argued U.S. southern realignments, coupled with the Bush administration’s unilateralism, presaged preemptive U.S. military action against North Korea, thus entrapping the South Korean people in an existential conflict not of its own choosing.²⁰  Note: For more on Seoul’s simultaneous fears about being abandoned and/or entrapped, see: Jonathan D. Pollack and Mitchell B. Reiss, “South Korea: The Tyranny of Geography and the Vexations of History,” in The Nuclear Tipping Point: Why States Reconsider Their Nuclear Choices, ed. Kurt M. Campbell, Robert Einhorn and Mitchell B. Reiss (Washington DC: Brookings Institution Press, 2004), 29.    Moreover, base closures and cleanups, along with land acquisition for U.S. facilities south of Seoul, were slowed by legal and political battles with an array of nongovernmental organizations (NGOs), activist groups, local communities, and the ROK Ministry of Environment. Although South Korea’s democratization had strengthened the alliance, the cacophonous set of voices it let loose made alliance management more complicated.²¹  Note: Katharine H.S. Moon, Protesting America: Democracy and the US-Korea Alliance (Berkeley: University of California Press, 2012), 6.    Above all, turnover in both U.S. and ROK leadership; an evolving North Korean threat; and shifting U.S. strategic calculus, whereby Washington sought to draw back from the Middle East and reorient toward the Asia-Pacific, altered plans to reduce and realign U.S. forces.²²  Note: Former U.S. four-star commander in Korea, interviewed by author, March 17, 2022; U.S. Military Official, interviewed by author, March 3, 2022.  

The George W. Bush administration had already decided to retain important elements of 2ID north of Seoul, including the division headquarters and key counterfire units, even though the ROK took over the counterfire mission in 2005. The ROK needed more time to train on new capabilities, and U.S. firepower was an important deterrent in the meantime. Furthermore, near the tail end of his administration, President George W. Bush and new conservative ROK President Lee Myung-bak halted further troop reductions, which meant the U.S. would retain 28,500 troops in the ROK. In addition to North Korea’s first nuclear test in 2006 and an uptick in ballistic and cruise missile tests thereafter, this decision was the result of fervent opposition from the Lee administration and U.S. military officials’ assessment that maintaining force level would be necessary to uphold deterrence and security.

Obama Reaffirms Topline Numbers Amidst the Pivot

The Obama administration, which had no intention of removing forces from South Korea, reaffirmed the 28,500 in 2009.²³  Note: Former U.S. four-star commander in Korea, interviewed by author, March 13, 2022.    The number 28,500 later found its way into successive annual defense authorization bills during the Trump years as a means to prevent him from suddenly removing U.S. forces as a consequence of displeasure over alliance cost-sharing disagreements.

Following North Korea’s provocations in 2010 with the sinking of the ROK Navy corvette Cheonan in March and shelling of Yeonpyeong Island in November, and its increase in nuclear and missile tests following Kim Jong Un’s coming to power, the Obama administration reaffirmed the decision to keep U.S. counterfire forces and 2ID headquarters north of the Han River, at least until the ROK’s own capabilities and plans were certified. At the same time, the alliance announced the establishment of the US-ROK combined division. This brought 2ID together with various ROK units to enhance “combinedness” during wartime at the tactical level and signify the U.S. rebalance to Asia.²⁴  Note: U.S. Military Official, interviewed by author, March 3, 2022; and Clint Work and Natalia Slavney, “North Korea’s “Checkerboard” Threat: Obstacles and Opportunities for the US-ROK Alliance,” 38 North, March 31, 2022, https://www.38north.org/reports/2022/03/north-koreas-checkerboard-threat-obstacles-and-opportunities-for-the-us-rok-alliance/.     As such, U.S. defense officials deactivated the 1st ACBT, 2ID’s last forward-stationed ground maneuver brigade, and transformed it into a nine-month, rotational deployment. Since then, various ACBTs have been deployed to the Korean Peninsula from the U.S.

The Pros and Cons of Rotational Deployments

The decision to replace the forward-stationed forces with rotational ones was driven, in part, by defense sequestration. 2ID’s 1st ACBT was deactivated due to defense budget cuts and the U.S. Army’s need to trim the force. However, there were concerns about base closures and unit deactivation in the U.S. Tapping contiguous U.S. (CONUS)-based ACBTs for rotational deployment to the Korean theater would help avoid such closures and keep units active.²⁵  Note: Ibid; and Former U.S. four-star commander in Korea, interviewed by author, March 17, 2022.    

The shift to rotational deployments was also motivated by the need to reinvigorate the Army after years of counterinsurgency in Iraq and Afghanistan, which had exhausted the force and reduced its preparedness for high-intensity conventional combat.²⁶  Note: Former U.S. four-star commander in Korea, interviewed by author, March 17, 2022.    The logic was that rotational deployments to the ROK would build unit cohesion and readiness since they undergo intense training before deployment and maintain a high operations tempo while in theater, which senior commanders contend bolsters assurance and deterrence.²⁷  Note: John R. Deni, Rotational Deployments vs. Forward Stationing: How Can the Army Achieve Assurance and Deterrence Efficiently and Effectively? (U.S. Army War College Press, 2017), xviii.    Rotational deployments were also a different way to build strategic flexibility into the U.S. force presence in the ROK, not so much for deployment on and off the peninsula to regional contingencies, but insofar as it built greater flexibility and mobility across the Army and greater familiarity with the region and South Korea. At any given time, three ACBTs are oriented to the ROK: one leaving, one arriving, and another training for future deployment.²⁸  Note: U.S. Military Official, interviewed by author, March 3, 2022.  

However, questions remain about the value of rotational units versus forward-stationed ones.²⁹  Note: It is unclear if rotational deployments bolster deterrence because adversaries may or may not see them as any more robust of a commitment than forward-stationed units. For allies, including the ROK, forward-stationed units are seen as a stronger, more enduring commitment. Rotational ACBTs come with higher levels of readiness, but forward-stationed units typically possess more knowledge of the culture, allied military units and counterparts, geography, and political leaders. They are more interoperable and culturally proficient forces; see: Deni, Rotational Deployments vs. Forward Stationing, xvii-xviii.    Moreover, when the Obama administration jettisoned a previous plan to normalize and lengthen forward-stationed tours in Korea from two to three years in favor of the rotational option, doing so may have undermined continuity and the ROK perception of U.S. commitment.³⁰  Note: Former U.S. four-star commander in Korea, interviewed by author, March 17, 2022.    Lastly, it is unclear whether or not rotational units are more costly than forward-stationed ones, which raises concerns in Seoul that their cost could be used as a reason not to deploy them. This became acute during the Trump years when Secretary of Defense Mark Esper and Secretary of State Mike Pompeo cited the cost of rotational deployments as one of the reasons Seoul needed to meet President Donald Trump’s exorbitant cost-sharing demands. Congressional staffers expressed concern Trump might simply allow one rotational ACBT to depart Korea and stop the next from going.³¹  Note: Author’s conversation with Professional Staff Member on the House Foreign Affairs Committee, February 15, 2020.  

Old Tripwires Removed, New Frictions Emerge

Along with the potentially negative, unintended effects of rotational deployments, the continued southern realignment of U.S. forces to hubs south of Seoul resulted in contradictory outcomes in the face of North Korea’s evolving capabilities. On the one hand, southern realignment raised traditional concerns among ROK observers about U.S. commitment insofar as it removed the so-called U.S. tripwire that was historically conceived as a U.S. presence perched between invading North Korean forces and the political and economic heart of South Korea. On the other hand, North Korea’s advancing capabilities meant U.S. forces south of Seoul were no less vulnerable to attack than those near the DMZ. In fact, the consolidation of most U.S. combat forces at regional hubs made them a “fat target” for North Korea.

The U.S. deployment of more advanced missile defense assets to the Korean Peninsula, most notably Terminal High Altitude Area Defense (THAAD) batteries in 2017, provided a modicum of protection. At the same time, doing so resulted in Beijing’s economic retaliation against Seoul for allowing the THAAD deployment, which China framed as an extension of U.S. strategic interests in the region. For South Korea, it did not need to agree to strategic flexibility for it to feel entrapped in a larger US-China confrontation.

The situation only worsened when President Trump initially argued South Korea should pay for the THAAD deployment, whereas in the original deal, the U.S. would cover the roughly $1 billion cost. Moreover, the progressive Moon administration pledged a Three No’s policy — no more THHAD, no ROK entry into the U.S. regional ballistic missile defense system, and no trilateral US-Japan-ROK security alliance — during a trip to China (to get sanctions alleviation) and highlighted the strategic bifurcation between Washington and Seoul.

For the remainder of the Trump-Moon years, there was constant debate about Seoul needing to abandon strategic ambiguity and make a clearer choice between Washington and Beijing, which ROK officials bristled against. At the same time, Trump administration officials and military commanders repeatedly spoke of U.S. forces in South Korea as being strategically flexible for use elsewhere in the region.

Consultation Without Cohesion

The reduction and realignment of U.S. forces have resulted in a lack of cohesion in core components of the alliance, which arguably is its most problematic consequence. A key underlying objective of changes in the U.S. force presence has been for the ROK to take on the leading role in conventional deterrence and defense on the Korean Peninsula, and it has largely done so. However, when it has exercised that responsibility both in the face of North Korean provocations and the gradual advancement of North Korean capabilities, it has met a discordant response from the U.S.

During North Korean provocations in 2010 and 2015, ROK officials perceived U.S. officials as being more concerned with restraining them than with North Korean provocations. The Lee Myung-bak administration’s argument that it needed to carve out self-defensive measures outside of the armistice rules of engagement and the Park Geun-hye administration’s talk of decapitation strikes against the North Korean leadership did not help. Although U.S. officials were concerned about North Korean aggressions and agreed that South Korea had the right to self-defense, their primary concern stemmed from the ROK making an overly retaliatory response.³²  Note: Former U.S. four-star commander in Korea, interviewed by author, March 17, 2022.    This was manifested in the South’s rollout of its own military systems to counter North Korea, most notably its Kill Chain preemptive strike system and its Korea Massive Punishment and Retaliation (KMPR) plan to punish and retaliate against North Korea in case it strikes South Korea. While these systems were still aspirational when first publicly introduced, U.S. officials were apparently not briefed beforehand.³³  Note: Former ROK military official, interviewed by the author, January 10, 2022.  

In this context of North Korea’s provocations and nuclear and missile testing campaign, ROK and U.S. alliance managers established a host of new consultative mechanisms on everything from counter-provocation and counter-missile strategy to a tailored bilateral deterrence strategy and U.S. extended deterrence. While indicative of rising concerns about the threat from North Korea and a genuine effort to enhance alliance cooperation, increased consultation did not change and often revealed divergent perspectives and the lack of cohesion between Washington and Seoul. South Korea, under the conservative Lee and Park administrations, saw alliance consultation on deterrence as a way to garner greater U.S. buy-in for a more robust response to DPRK provocations, and U.S. officials saw it as a restraining device.³⁴  Note: Ibid.    During the Trump-Moon years, some of these consultative groups stopped meeting due to diplomatic efforts with Pyongyang, while in others, both sides talked past one another while publicly extolling their enhanced cooperation.³⁵  Note: Clint Work, “Psychological & Institutional Limits: Trump & the Future of the US-ROK Strategic Alliance,” in Divided America, Divided Korea: US-Korean Relations During and After the Trump Years, edited by Mitchell B. Lerner and David P. Fields (New York: Columbia University Press, 2022 forthcoming).  

Current Context

As a result of these developments, the alliance is currently confronted by the waning credibility of the U.S. extended deterrence commitment itself. This particular commitment consists of a range of capabilities, including U.S. troops, conventional strikes and missile defense assets already in Korea, the deployment of massive follow-on forces during a conflict and the U.S. nuclear umbrella. However, as the U.S. has gradually reduced and realigned its forces, the ROK military, as previously noted, took on primary responsibility for conventional deterrence. U.S. troops in Korea provide significant air, firepower, C4ISR, and ground maneuver capabilities. Yet, most U.S. forces are support and logistical units whose primary function is to facilitate the arrival of additional forces in the event of a conflict.³⁶  Note: U.S. Military Official, interviewed by author, March 3, 2022    

Meanwhile, North Korea’s advancements have transformed the peninsula into an anti-access/area-denial environment, which has constrained the United States’ ability to deploy such forces to the Korean theater and has made U.S. regional hubs in the ROK easy targets. Consequently, ROK capabilities have become even more central to the deterrence and warfighting equation. In short, Seoul’s concerted effort over the last 15 years to acquire or indigenously develop high-end conventional capabilities has come a long way. Yet, as a result of that same process, South Korea has placed more scrutiny on the credibility of the U.S. nuclear umbrella.

During annual meetings, U.S. alliance managers have sought to reassure their ROK counterparts via new consultative mechanisms of the credibility, capability, and enduring nature of the U.S. extended deterrence commitment, particularly the nuclear umbrella, but ROK officials have not been reassured. Seoul’s skepticism has shown in its calls for greater allied consultation on U.S. nuclear policy, a nuclear sharing agreement, or the redeployment of U.S. tactical nuclear weapons — none of which Democratic or Republican administrations have been willing to grant.

Watching U.S. withdrawals from Afghanistan and Ukraine as they are sacrificed to great power politics has only increased South Korea’s doubts and insecurities. There are mounting calls within the ROK for the country to develop its own nuclear weapons and pursue nuke-to-nuke deterrence with the DPRK. Survey data shows 70 percent of South Koreans agree, with many pointing to great power competition as much as North Korea as their motivation. Currently, there is growing divergence regarding conventional and nuclear deterrence on the Korean Peninsula, with alliance fissures, crisis miscalculation, strategic instability, and the unraveling of the nuclear nonproliferation regime all possible consequences.

Conclusion

Concern about the lack of cohesion has dissipated to some degree due to the Biden administration’s prioritization of U.S. alliances as critical components of an increasingly complex and shifting strategic environment. It is an environment in which democracy is being pitted against authoritarianism, international norms, and respect for sovereignty versus a return to sphere-of-influence politics. The May 2021 presidential summit between Presidents Biden and Moon was viewed by analysts as a key indicator of stabilized alliance relations, particularly after four rocky years of Trump’s antagonistic approach to alliances. Congress has removed clauses in annual defense authorization bills about minimum troop numbers, and the Biden administration affirmed it would maintain and even increase force levels, including permanently stationing an attack helicopter squadron and artillery division headquarters in the ROK.

The inauguration of South Korea’s new president Yoon Suk-yeol has most alliance watchers preparing for tighter alliance relations, which is usually the case under conservative administrations. President Yoon has struck all the right chords for the establishment in Washington by stating his support for the following: bolster deterrence against North Korea and enforce sanctions, restart and ramp up military exercises, tighten trilateral US-Japan-ROK relations, shift from a position of strategic ambiguity to strategic clarity and actively support the Biden administration’s Indo-Pacific strategy. Nonetheless, there are various problematic trends that will continue to complicate things. Like the United States’ harried withdrawal from Afghanistan, the war in Ukraine and confrontation with Russia has and will continue to absorb the bulk of the Biden administration’s bandwidth. Not only does this mean fewer U.S. resources will be directed to South Korea or East Asia more broadly, but it is likely to raise further questions about the degree to which the U.S. will honor its security commitments.

At a time when North Korea is moving full steam ahead with advancing its asymmetric capabilities, Yoon has been outspoken in saying that the U.S. needs to deploy more strategic assets and show greater fidelity regarding U.S. extended deterrence policy toward North Korea, including reactivating some of the aforementioned consultative mechanisms. Yet, if history is any indication, U.S. officials will continue to try and reassure their ROK counterparts while holding their cards close when it comes to U.S. nuclear policy, leaving South Korea feeling perpetually left out. Simultaneously, President Yoon intends to ramp up the ROK’s own indigenous three-axis system, further develop preemptive strike capabilities, enhance THAAD deployments and establish a strategic command. This could result in Washington exerting considerable pressure on Seoul to share details about its own acquisitions program and preemptive strategy and to not escalate an already tense and combustible situation in the context of Pyongyang testing and possible provocations.

China’s assertiveness, the South Korean public’s increasingly negative opinion toward Beijing, and the threat of North Korea may actually work to instill greater alliance cooperation. However, greater cooperation does not necessarily mean greater cohesion, as happened throughout the 2010s and could very well happen again. Furthermore, political conditions change. Trump or a Trump-like candidate may run and prevail in 2024, once again creating space for the lack of alliance cohesion to burst open at a time when the stakes and risks are even higher. As such, U.S. and ROK alliance managers must not waste any more time, as they urgently need to engage one another in tough but honest consultations. If the alliance is as ironclad, broad, and deep as they say it is, it can not only withstand such talks, but it also requires them.

Notes

• 1
    Note: The most often cited example is Dean Acheson’s January 12, 1950 remarks at the National Press Club, which declared a consolidated security perimeter for Asia that excluded South Korea and Taiwan from areas of vital U.S. interest. However, General Douglas MacArthur had described the defense perimeter in very similar terms in March 1949. See: Samuel F. Wells Jr., Fearing the Worst: How Korea Transformed the Cold War (New York: Columbia University Press, 2020), 21, 58-59.  
• 2
    Note: Wells Jr., Fearing the Worst; see also: Robert Jervis, “The Impact of the Korean War on the Cold War,” The Journal of Conflict Resolution 24, no. 4 (December 1980): 563-592.  
• 3
    Note: Kwang Sub Kwak, “The United States-ROK Alliance, 1953 — 2004: Alliance Institutionalization” (Ph.D. dissertation, Southern Illinois University at Carbondale, 2006), 66-90.  
• 4
    Note: As stated in my previous work, initially, the meaning of the tripwire was quite literal: minimal U.S. ground troops on the frontline whose presence guaranteed immediate U.S. involvement in another Korean conflict. These forward-deployed ground troops were militarily necessary to slow down advancing North Korean forces to allow time for contiguous U.S. (CONUS)-based reinforcements to arrive; they were also a credible physical manifestation of the U.S. commitment to South Korean security embodied in the US-ROK Mutual Defense Treaty (MDT). No president or Congress would stand idly by as tens of thousands of U.S. military and civilian personnel were killed in the early stages of a conflict.  
• 5
    Note: U.S. Congress, House, Committee on International Relations, Investigation of Korean-American Relations: Report of the Subcommittee on International Organizations, 95th Cong., 2d sess., 1978, H. Rep., 61. (also known as the “Fraser Report”), 63, footnote 56.  
• 6
    Note: Henry Kissinger, The White House Years: Vol. II: Years of Upheaval (Boston: Little, Brown, 1982), 308.   
• 7
    Note: Clint Work, “A Fly in Amber: Carter’s Korea Troop Withdrawal & The Recasting of U.S. Hegemony and Korean Agency” (Ph.D. dissertation, University of Washington, Seattle, 2019).   
• 8
    Note: Ibid, 431.  
• 9
    Note: Carl Ford, interview by the author, June 4, 2021; see also: Michael J. Green, By More Than Providence: Grand Strategy and American Power in the Asia Pacific Since 1783 (New York: Columbia University Press, 2019), 445, footnote 92.     
• 10
    Note: Carl Ford, interview by the author, June 4, 2021.  
• 11
    Note: Kwak, “The United States-ROK Alliance, 1953 — 2004,” 90.  
• 12
    Note: Yoichi Funabashi, Alliance Adrift (New York: Council on Foreign Relations Press, 1999), 249.  
• 13
    Note: Carl Ford, interview by the author, June 4, 2021  
• 14
    Note: Joseph S. Nye Jr., interview by the author, December 23, 2021.  
• 15
    Note: Michael Finnegan, interview by the author, June 10, 2021; see also, Funabashi, Alliance Adrift, 273.  
• 16
    Note: Yoichi Funabashi, The Peninsula Question: A Chronicle of the Second Korean Nuclear Crisis (Washington DC: Brookings Institution Press, 2007), 230-261.  
• 17
    Note: Richard Lawless, interview by the author, October 23, 2021; and Michael Finnegan, interview by the author, June 10, 2021.  
• 18
    Note: U.S. Military Official, interviewed by author, March 3, 2022.  
• 19
    Note: Richard Lawless, interview by the author, October 23, 2021; Michael Finnegan, interview by the author, June 10, 2021.  
• 20
    Note: For more on Seoul’s simultaneous fears about being abandoned and/or entrapped, see: Jonathan D. Pollack and Mitchell B. Reiss, “South Korea: The Tyranny of Geography and the Vexations of History,” in The Nuclear Tipping Point: Why States Reconsider Their Nuclear Choices, ed. Kurt M. Campbell, Robert Einhorn and Mitchell B. Reiss (Washington DC: Brookings Institution Press, 2004), 29.  
• 21
    Note: Katharine H.S. Moon, Protesting America: Democracy and the US-Korea Alliance (Berkeley: University of California Press, 2012), 6.  
• 22
    Note: Former U.S. four-star commander in Korea, interviewed by author, March 17, 2022; U.S. Military Official, interviewed by author, March 3, 2022.  
• 23
    Note: Former U.S. four-star commander in Korea, interviewed by author, March 13, 2022.  
• 24
    Note: U.S. Military Official, interviewed by author, March 3, 2022; and Clint Work and Natalia Slavney, “North Korea’s “Checkerboard” Threat: Obstacles and Opportunities for the US-ROK Alliance,” 38 North, March 31, 2022, https://www.38north.org/reports/2022/03/north-koreas-checkerboard-threat-obstacles-and-opportunities-for-the-us-rok-alliance/.   
• 25
    Note: Ibid; and Former U.S. four-star commander in Korea, interviewed by author, March 17, 2022.    
• 26
    Note: Former U.S. four-star commander in Korea, interviewed by author, March 17, 2022.  
• 27
    Note: John R. Deni, Rotational Deployments vs. Forward Stationing: How Can the Army Achieve Assurance and Deterrence Efficiently and Effectively? (U.S. Army War College Press, 2017), xviii.  
• 28
    Note: U.S. Military Official, interviewed by author, March 3, 2022.  
• 29
    Note: It is unclear if rotational deployments bolster deterrence because adversaries may or may not see them as any more robust of a commitment than forward-stationed units. For allies, including the ROK, forward-stationed units are seen as a stronger, more enduring commitment. Rotational ACBTs come with higher levels of readiness, but forward-stationed units typically possess more knowledge of the culture, allied military units and counterparts, geography, and political leaders. They are more interoperable and culturally proficient forces; see: Deni, Rotational Deployments vs. Forward Stationing, xvii-xviii.  
• 30
    Note: Former U.S. four-star commander in Korea, interviewed by author, March 17, 2022.  
• 31
    Note: Author’s conversation with Professional Staff Member on the House Foreign Affairs Committee, February 15, 2020.  
• 32
    Note: Former U.S. four-star commander in Korea, interviewed by author, March 17, 2022.  
• 33
    Note: Former ROK military official, interviewed by the author, January 10, 2022.  
• 34
    Note: Ibid.  
• 35
    Note: Clint Work, “Psychological & Institutional Limits: Trump & the Future of the US-ROK Strategic Alliance,” in Divided America, Divided Korea: US-Korean Relations During and After the Trump Years, edited by Mitchell B. Lerner and David P. Fields (New York: Columbia University Press, 2022 forthcoming).  
• 36
    Note: U.S. Military Official, interviewed by author, March 3, 2022