The Resilient US-South Korean Alliance

There is a sort of stickiness to the United States’ physical military presence in and security commitment to South Korea. Over the years, despite periods of uncertainty in the U.S.-South Korea relationship and plans to drawdown or even remove U.S. military forces, the American presence remains. Trace over the decades-old relationship and one observes some basic patterns, rooted in the historical origins of the relationship, yet still salient today.

Indeed, it is during those periods of uncertainty and potential change when the patterns become most apparent, and also in the wake of such periods that they have been, in a sense, reinforced. Although the U.S. presence in South Korea and U.S.-ROK alliance has undoubtedly evolved, these patterns are remarkably consistent. They have been affirmed by generations of U.S. policymakers, evinced in countless public statements, primary documents, and actual policy. So, what are they? And, further, how might they be changing?

The first pattern is that the U.S. presence in and commitment to South Korea is almost entirely derivative of and subordinate to several larger, interrelated U.S. interests. The most immediate is the security of Japan, one of America’s most important strategic and political economic allies, and by extension the preservation of peace and stability in Northeast Asia. Regional stability, in turn, is seen as vital to American national security, as well as the health of the capitalist world economy.

Underpinning this is the general U.S military force structure in the Western Pacific, within which the Korean Peninsula is conceived of as a key outpost, not due to any innate value so much as its bearing on wider strategic concerns. Indeed, in the early post-WWII period, U.S. military strategists had no strategic interest in Korea and saw it as a strategic liability, militarily inconsequential in and of itself. However, once established after the Korean War, peninsula-based U.S. forces’ forward, mainland deployment offered closer access to China and the USSR in the case of a larger conflict. Moreover, the immediate threat on the divided Korean Peninsula provided a platform for high-level preparedness and training for U.S. troops, and their later deployment to wars in Vietnam and elsewhere. In fact, in the late 1970s the U.S. military strongly opposed U.S. President Jimmy Carter’s abortive troop withdrawal policy, citing not only the importance of the U.S. forces’ deterrent role but also the unique training advantages provided by the highly militarized environment.

Most broadly, U.S. officials see the U.S. military presence in South Korea as a symbol of American credibility. According to this view, the peninsular commitment is inextricably bound up with wider international perceptions regarding the credibility of U.S. commitment. It possesses political and psychological significance far beyond its local dimensions. One scholar has referred to it as the Unwanted Symbol, accurately describing its derivative yet disproportionate significance. In the wake of the ignominious U.S. withdrawal from Vietnam in 1975 and as the last remaining mainland U.S. deployment in Asia, South Korea’s importance was only reinforced; yet another reason given for opposition to Carter’s withdrawal policy.

The second pattern is that the United States is the ultimate guarantor of South Korea’s external security, and has been for nearly its entire existence. Soon after WWII, American combat forces were first stationed on southern Korean territory and the United States established the U.S. Army Military Government in Korea (USAMGIK, 1945-1948). South Korea did not yet exist, and these U.S. combat forces as well as U.S. efforts at the United Nations were integral to its creation as a sovereign state on August 15, 1948. U.S. troops remained there until June 1949, leaving behind a 500-man detachment of military advisors. Notably, from June 1949 until just after the outbreak of the Korean War on June 25, 1950, is the only period in South Korea’s history when U.S. combat troops have not been present. Furthermore, had U.S. combat troops and airpower not been reintroduced at the start of the Korean War, the fragile, two-year old South Korean state would have been swallowed whole by the Soviet-backed, North Korean military. Put simply, the United States helped create, save, and (with the exception of that one year) has protected South Korea since its inception. In this sense, the physical presence of the U.S. military is tied inextricably to South Korea’s external sovereignty.

An important dynamic behind this pattern is the U.S. desire to maintain relative control or influence over the local environment, including over the policies and actions of its South Korean ally. Historically speaking, the desire was grounded in: U.S. reticence to take on an Asian mainland commitment; its inability to disaggregate that commitment from concrete regional imperatives as well as more intangible questions of U.S. credibility; and U.S. officials’ difficulty in dealing with South Korea’s first president, Syngman Rhee, and his persistent attempts to disrupt events and draw the U.S. into greater involvement before, during, and after the Korean War.

The United States was able to maintain overwhelming influence due to the stark asymmetry in the relationship and because South Korea depended on the U.S. for its very survival. In the early Cold War years, the ROK military was almost entirely dependent on the U.S. for material, armaments, ammunition, and spare parts. Its units and training mirrored the U.S. example in isomorphic fashion, and the United States maintained significant pull within the ROK military, including over promotions in the officer corps. The United States also possessed notable influence over South Korea’s defense modernization. Successive U.S. administrations restricted the kind of weaponry South Korea possessed, and the pace at which it developed new capabilities, from certain kinds of missiles and aircraft to Seoul’s own nuclear weapons.

In addition, a key condition for ratification of the 1954 U.S.-ROK Mutual Defense Treaty and maintenance of U.S. forces in South Korea was the local four-star U.S. general’s retention of operational control (OPCON) of the South Korean military. Such deliberately instituted measures and command arrangements allowed the United States to limit the ROK’s ability to undertake more aggressive and potentially destabilizing policies toward North Korea in response to Pyongyang’s many provocations. Although the long-term U.S. objective, which was gradually achieved, was to increase ROK defense capabilities, lessen its dependence on U.S. assistance, and pass off more local responsibility to Seoul, American officials maintained inordinate constraints over their smaller ally.

Once again, it was during the Carter administration that the Combined Forces Command (CFC) was established, which, among other things, was a cooperative means for dealing with his troop withdrawal policy. Of note, part of the opposition to the policy was borne of U.S. officials’ concern regarding the loosening of control and contradictions that would arise as a consequence of the withdrawal. They surmised the new command arrangement would lead Seoul to take back OPCON and result in a mismatch between a U.S. general overseeing the armistice while commanding a much reduced U.S. presence, which would lack any actual ground combat component. However, Carter’s plan was first delayed, then put in abeyance, and eventually canceled under Reagan.

Another important aspect of the U.S. desire to wield influence was the perceived role of the ROK military. From the earliest formation of the Korean constabulary under American auspices during the USAMGIK period, U.S. officials aimed to create an interdependent yet indigenous anti-communist force as a supplement to overall free-world forces. In later years, the supplementary role of the ROK military was made more explicit with President Lyndon B. Johnson’s “More Flags Campaign” and attendant pressure on Seoul to provide combat forces in Vietnam, as well as the later inclusion of ROK forces in U.S. Total Force Planning under Nixon’s Secretary of Defense Melvin Laird.

Little known to most Americans, South Korea deployed more troops per capita to the Vietnam War than any other country, including the United States itself. In other words, the flip side of the local U.S. commitment to ROK security, wherein the United States bolstered South Korean defenses, was the tacit understanding that ROK forces would serve the reverse purpose, namely, inclusion in U.S. strategic planning and policy (read: wars) beyond the peninsula. Years later this included a small detachment of military medics in Desert Storm, and several thousand medical, peacekeeping, and engineering personnel during the second U.S. war in Iraq. Although smaller, non-combatant deployments, American and South Korean policymakers alike saw them as an essential element of alliance cooperation.

Importantly, this was not a passive arrangement, to which Koreans were unwittingly subject. From their perspective, being a junior partner or client in the larger U.S. Cold War project provided numerous military, political, and economic advantages; advantages they were quick to leverage. In fact, successive leaders often proved eager to play a supplementary role in U.S. conflicts even before the Americans were willing to accept such contributions. This was manifest under Syngman Rhee, Park Chung-hee, and explicitly under Chun Doo-hwan, who spoke of the ROK as an American “strategic asset” in order to secure U.S. support for his regime and bolster his tenuous domestic legitimacy.

The above patterns have surely evolved. Nevertheless, following uncertain periods like the 1970s, during which they were challenged, they just as quickly settled in again – if in slightly altered form. Today, we are witnessing a similar evolution, wherein the patterns are being reconstituted and may even be coming undone.

First, Pyongyang’s advancing nuclear and missile capabilities have altered an originally local U.S. commitment, subordinate to larger interests, into one possessing more innate strategic significance. For the United States, what was once a case of extended deterrence (defending a distant ally in Seoul) has transformed into one of immediate deterrence (confronting a potential threat to the U.S. mainland). In conjunction, these developments expand a peninsular confrontation with mostly conventional arms (which continues) into a serious problem of global proliferation, with possibly dire implications for the nuclear nonproliferation regime. Furthermore, the inherent importance of South Korea as a key outpost has increased, with U.S. Army Garrison Humphreys in Pyeongtaek, 40 miles south of Seoul, soon to become the largest overseas American military base in the world. Nevertheless, the U.S. presence is still embedded within (and derivative of) wider U.S. imperatives, with both the Obama and Trump administrations calling the U.S.-ROK alliance the “linchpin” of the Pivot to Asia and later the “free and open Indo-Pacific” U.S. strategy. U.S. disclaimers notwithstanding, this regional strategy undoubtedly has China in its sights.

Next, recent developments also relate back to the second pattern above (namely, the United States being the guarantor of Seoul’s external sovereignty). In a manner, this has been reinforced, with Seoul still dependent on the U.S. nuclear umbrella as the ultimate deterrent against North Korean attack. Additionally, Seoul depends on crucial U.S. intelligence and early warning capabilities, even for its own ostensibly independent Korea Air and Missile Defense (KAMD) system. Also, over the last 20 years, the U.S.-ROK alliance has become progressively more interoperable and combined operations more tightly bound. However, fissures do exist.

Pyongyang’s steady nuclear and missile advancements have begun to expose a growing divide between Washington D.C. and Seoul’s order of preferences vis-à-vis Pyongyang’s weapons and denuclearization. While the former repeatedly states that any North Korean nuclear weapons are unacceptable and shows an increasing (rhetorical) willingness to tolerate military strikes, the latter prioritizes peace above all else and even indicates a “freeze” arrangement might be acceptable, which, though not explicitly stated, opens space for Pyongyang’s retention of some sort of nuclear capability. The emerging dynamic cuts against aspects of the second pattern.

For one, Seoul is increasingly concerned about being entrapped by precipitous U.S. military action against North Korea. As stated elsewhere, this represents a historic irony and inversion of roles; Seoul now hopes to restrain its larger ally. Relatedly, Washington is finding it more difficult to incorporate Seoul into its wider vision and policy. On both North Korea and in regard to the so-called “free and open Indo-Pacific,” Seoul is demonstrably reticent if not outwardly defiant in adhering to Washington’s preference. Seoul will not accept more U.S. missile defense assets nor enter the U.S.-led regional missile defense system, and it is not interested in turning trilateral U.S.-ROK-Japan cooperation into anything approximating a military alliance (the so-called “three nos”). Despite South Korea and China’s real and lingering differences, Seoul’s “balanced diplomacy” and view of North Korean denuclearization is consonant with Beijing’s preferences. From Washington’s perspective this is problematic. Lastly, President Moon Jae-in is moving to regain full wartime OPCON from the United States, and, much to the chagrin of his conservative opponents, eagerly frames the move in terms of national sovereignty and independence.

To be fair, these changes are not necessarily new. Some emerged with the first North Korean nuclear crisis in the early 1990s. Furthermore, a decade of progressive administrations within South Korea (1998-2008) marked a decidedly more independent orientation on the part of Seoul in relation to their longtime U.S. ally. In short, the U.S. presence in South Korea and U.S.-ROK alliance is a deep-seated security and political architecture, which has not and will not rapidly change. Nevertheless, the mixed (if not confused) signals sent by the Trump administration and the existential questions confronting Seoul may push the evolution into higher gear. Only time will tell.