Table of Contents

The Primacy of Politics on the Korean Peninsula

The security environment on the Korean Peninsula is more uncertain than at any other time since the end of the Cold War. Despite two decades of diplomatic efforts, international sanctions, and even military pressure, neither the United States nor South Korea could prevent North Korea from acquiring nuclear weapons. Under Supreme Leader Kim Jong Un, who has been in power since December 2011, North Korea has become a de facto nuclear-weapon state. Pyongyang detonated its first hydrogen bomb in September 2017 and tested an upgraded submarine-launched ballistic missile (SLBM) in October 2019.1

Going into the 2020s, South Korea faces unparalleled military challenges. Beyond the expanding threats emanating from North Korea, China’s increasingly aggressive military posture poses new quandaries. Unlike Japan, South Korea is much more reticent about calling out Beijing on a range of security concerns due to its geographic proximity, the sheer magnitude of China’s geopolitical weight in and around the Korean Peninsula, and Beijing’s influence over North Korea. Nevertheless, just because Seoul does not publicize its discomfort with China, that does not mean that South Korea ignores China’s growing military footprint. Indeed, throughout history, arguably no Asian country has been on the receiving end of Chinese aggression more than Korea has.

On top of coping with growing North Korean and Chinese military capabilities (not to mention Russia, a formidable military power that remains closely aligned with China), South Korea also has to undertake massive military reforms throughout the 2020s, which include paring down its armed forces from 599,000 to 500,000 troops due to the country’s rapidly declining birthrates and the limited available pool of conscripts.2 Moreover, alliance cohesion has suffered due to U.S. President Donald Trump’s mercurial Korea policies, including his constant pressure on South Korea to drastically increase its common defense contributions. Last but not least, President Moon Jae-in’s engagement with North Korea has not resulted in key security dividends or slowed the pace of North Korea’s accelerating nuclear weapons program.

Chung Min Lee
Chung Min Lee is a senior fellow in Carnegie’s Asia Program. He is an expert on Korean and Northeast Asian security, defense, intelligence, and crisis management.
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Numerous factors come into play when determining a country’s threat perceptions. The range of military threats emanating from an adversary or adversaries, the political and strategic calculus of the top political and military leadership, demonstrable combat capabilities, and the degree of external military assistance are all relevant considerations. But equally trenchant is how a host nation’s leadership perceives the core threats it faces.

Moon and Trump have elevated personal outreach with the Kim regime to a level far beyond that of their predecessors. The years 2018 and early 2019 marked a period of whirlwind diplomacy, with three inter-Korean summits. Most significantly, Trump met with Kim in June 2018 in Singapore for the first-ever U.S.–North Korea summit. A second U.S.–North Korea summit was held in Hanoi in February 2019. In addition to these meetings, Kim held key summits with Chinese President Xi Jinping and his first meeting with Russian President Vladimir Putin. Moon wanted to achieve a breakthrough in inter-Korean relations and was convinced that Kim would be willing to accommodate him. Absent any major foreign policy victory during his first term, Trump wanted to show the world that, unlike previous U.S. presidents, he had the ability to make an unparalleled nuclear deal with Kim.

Throughout the fall of 2017 when North Korea escalated tensions, Trump pushed back by stating that he would obliterate North Korea if he had to. By early 2018 when North Korea decided to join the Winter Olympic Games in Pyeongchang, South Korea, Trump also shifted gears. Moon was very eager to foster U.S.–North Korea dialogue since he believed that a major breakthrough in ties between Washington and Pyongyang would result in critical payoffs for Seoul. From the moment Trump shook hands with Kim in Singapore in June 2018, Trump highlighted his personal rapport with the North Korean leader. Subsequently, Trump played down North Korean provocations by arguing that Kim was ultimately going to conclude a major nuclear deal with him. For instance, when North Korea fired a short-range missile in July 2019, Trump remarked that “they’re short-range missiles. And my relationship is very good with Chairman Kim. And we’ll see what happens. But they are short-range missiles, and many people have those missiles.”3 Nuclear expert Vipin Narang highlighted the naiveté of this statement when he wrote that “these [missiles] are mobile-launched, they move fast, they fly very low and they are maneuverable. That’s a nightmare for missile defense.”4 He went on to note that “Kim is exploiting loopholes in his agreements with President Trump brilliantly.”

Despite the unprecedented meetings of 2018 and 2019, neither Moon nor Trump were able to achieve breakthroughs with North Korea. While Trump deserves credit for being the first sitting U.S. president to hold direct meetings with Kim, he has been instrumental in weakening alliance cohesion more than any other U.S. president. Trump’s wild rhetoric, penchant for the limelight, and cavalier treatment of alliance management issues have created unease in South Korea, but for the most part, the Moon administration has chosen to live with Trump’s antics. This is because Seoul does not want to curtail Washington’s potential rapprochement with Pyongyang or dampen Trump’s outreach to Kim. Given that Moon’s highest priority lies in creating an irreversible peace regime on the Korean Peninsula, he has been willing, for the time being, to push aside Trump’s incessant calls for an exponential increase in South Korea’s contributions for the common defense.

This is not to suggest that the Republic of Korea (ROK) military, the Pentagon, and the U.S. forces stationed on the peninsula are not prepared for worst-case scenarios. But Trump’s constant pressure on South Korea to pay more for stationing U.S. troops on the peninsula, incessant denigration of U.S.-ROK joint military exercises as too expensive and threatening, constant berating and second-guessing of the U.S. intelligence community, and amateurish foreign policy decisionmaking have contributed to a fundamental unease in the U.S.-ROK alliance. In some respects, the state of the U.S.-ROK alliance today is reminiscent of the alliance in the late 1970s when Seoul adamantly opposed then U.S. president Jimmy Carter’s initial promise to gradually withdraw U.S. ground forces from South Korea. But Carter ultimately listened to new intelligence estimates that led him to roll back his withdrawal plans; most importantly, while Carter came into office with very different views on South Korea and developments on the Korean Peninsula, he never disrespected the intelligence community or the military services.

The year 2019 is likely to be remembered as a tipping point on the Korean Peninsula, when the combined efforts of Trump and Moon softened deterrence and defense against North Korea.

The year 2019 is likely to be remembered as a tipping point on the Korean Peninsula, when the combined efforts of Trump and Moon softened deterrence and defense against North Korea. If Trump is re-elected in November 2020, he may be emboldened to conduct a partial withdrawal of U.S. forces from South Korea, particularly if Seoul does not meet his cost-sharing demands.

Fortunately, the U.S. Senate passed a resolution in December 2019 that stipulated that the president cannot reduce the number of the United States Forces Korea (USFK) troops on the peninsula below 28,500, the current number.5 The bill noted, in part, that “while the conferees support diplomatic efforts to achieve the complete and fully verified denuclearization of the Democratic People’s Republic of Korea, the conferees believe the removal of United States military forces from the Korean Peninsula is a non-negotiable item in such negotiations.” (The bill stipulates that the U.S. secretary of defense must certify that a reduction would not significantly “undermine the security of United States allies in the region” and that the Department of Defense has “appropriately consulted allies of the United States, including South Korea and Japan, regarding such a reduction.”)6

Hopes of Peace, Signs of Trouble

Eye-catching diplomatic overtures took center stage throughout 2018 and into early 2019, though Trump and Moon’s bids for a nuclear breakthrough came up empty. For his part, Kim ushered in 2019 with a noteworthy New Year’s address that seemed conciliatory on the surface but also hinted at continued North Korean intransigence. He praised the socialist path his country is taking and stressed the importance of normalizing ties with the United States to the extent that Washington was willing to alter its hostile policy toward North Korea. “I am ready to meet the U.S. president again anytime, and will make efforts to obtain without fail results which can be welcomed by the international community,” Kim stated.7 Yet despite this diplomatic language, Kim’s address also contained a harder edge. While holding out his hand to Trump, Kim also warned that if the United States did not keep what he construed to be its promise, North Korea “may be compelled to find a new way for defending the sovereignty of the country and the supreme interests of the state and for achieving peace and stability.”

As expected, the Moon government welcomed Kim’s speech and remained hopeful that 2019 would be a pivotal year for inter-Korean relations. In his own New Year’s press conference, Moon was upbeat about Kim’s pledge, despite delays, to visit Seoul if circumstances permitted, and the South Korean president explained that the two leaders would continue to meet throughout 2019. Moon also reiterated the importance of signing an end of war declaration in 2019: “The signing of a peace agreement was part of the plan under the armistice agreement so that within six months, all aspects of the war would come to a conclusion with the signing of a peace agreement.” He went on to say, “If adversarial relations between the two sides can be reduced with a parallel political statement, denuclearization efforts will pick up momentum and as a result, peace negotiations can also bear fruit.”8

Seoul continued to stress inter-Korean détente as ties between the United States and North Korea dominated the headlines going into the February 2019 Hanoi summit. For instance, the first ROK defense white paper published under the Moon administration in 2018 differed markedly from those published under the previous administration of conservative president Park Geun-hye. Unlike the 2016 edition, the country’s 2018 defense white paper took out references to North Korea being an “enemy.”9 Instead, the Moon administration white paper noted:

The ROK Armed Forces considers any force that threatens and violates the sovereignty, territory, people, and properties of the Republic of Korea as an enemy. The relationship between South and North Korea has alternated between military confrontation, reconciliation, and cooperation. However, an unprecedented security environment has been set in 2018 to realize complete denuclearization and peace establishment on the Korean Peninsula through three successful inter-Korean summits as well as the first-ever U.S.-DPRK [Democratic People’s Republic of Korea] summit.10

This mood of diplomatic optimism persisted through the rest of 2018 and into the following year. In September 2018, Moon and Kim signed an agreement on implementing military aspects of the historic April 2018 Panmunjeom Declaration referred to as the Comprehensive Military Agreement. Moon’s 2018 defense white paper stated that the Ministry of National Defense would pursue arms control measures and confidence-building measures (CBMs) as progress was achieved on denuclearization and peace talks. As the white paper put it, “The denuclearization of the Korean Peninsula and the establishment of a peace regime will put an end to the long-standing division and confrontation, laying the stepping stones toward co-existence and mutual prosperity.”11

There has been a significant mismatch between these optimistic sentiments and Korea’s unchanged security landscape. If South Korea did not face one of the world’s most dangerous and complex threat spectrums, the Ministry of National Defense could be excused for publishing an assessment replete with references to building peace, fostering diplomacy, preparing for a transformed U.S. alliance, and laying the foundation for inter-Korean military CBMs and arms control. There is nothing inherently wrong with such aims. Rather, the problem lies in equating peace-seeking measures with tangible changes in North Korea’s overarching war aims, military capabilities, grand strategy toward South Korea, and prospects for North Korea’s denuclearization. After all, North Korea has taken no appreciable steps to meaningfully reduce its military forces or revise its military doctrine.

Despite the euphoria of 2018 and early 2019, the failure of the U.S.–North Korea Hanoi summit in February 2019 reinforced existing strategic realities; namely, North Korea’s military posture toward South Korea had not changed for the better nor had the North Korean military’s training regimen shifted considerably. There was no indication that North Korea’s nuclear weapons and ballistic missile programs were curtailed. Even so, the Moon government continued to maintain that Kim was fully committed to denuclearization and that the two Koreas had turned over a new leaf.

Predictably, North Korea simultaneously tried to sell hopes of a breakthrough in U.S.–North Korea talks while continuing to upgrade its arsenal. On November 15, 2018, while Pyongyang continued to maintain a self-imposed moratorium on testing nuclear warheads and intercontinental ballistic missiles (ICBMs), it announced the successful testing of a “a new tactical weapon.” North Korea’s state-affiliated newscasters reported that “after seeing the power of the tactical weapon, Supreme Leader Kim Jong-un was so excited to say that another great work was done by defense scientists and munitions industrial workers to increase the defense capability of the country.”12 Similarly, mere months after the collapse of the February 2019 Hanoi summit, North Korea resumed conducting projectile and short-range missile tests (for a total of twenty-one tests in 2019).13

Pyongyang continued to demonstrate new military capabilities in 2019. On October 3, 2019, North Korea announced that it had tested a new SLBM with a range of about 450 kilometers and an altitude of 910 kilometers. The Pukguksong-3 missile was not actually launched from a submarine and, according to the BBC, “North Korea’s engineers may have deemed it too risky to stake their one operational ballistic missile submarine in a test.” Still, the broadcaster concluded that the missile passed the flight test on the technical merits “with flying colors.”14 An October 2019 Foreign Policy article called the test “a major technical achievement” even if the missile is not deployed for several years.15

The Pukguksong-3 test illustrated North Korea’s ability to field an SLBM with an estimated range of 1,900 kilometers, according to the CSIS Missile Defense Project, would be highly challenging for U.S. and South Korean missile defense systems to detect early or destroy.16 More fundamentally, as the aforementioned Foreign Policy article reported, “in the absence of any concrete nuclear deal with the United States, North Korean leader Kim Jong Un continues to assemble, piece by piece, a sophisticated nuclear weapons arsenal and the capacity to deliver those weapons on neighboring countries.”17 Despite Moon’s and Trump’s downplaying of the North Korean threat and the hopes they have pinned on a nuclear deal, North Korea demonstrated in the latter half of 2019 that it has little desire to pursue genuine denuclearization talks with the United States.

Pyongyang did not stop with the Pukguksong-3 test. On November 29, 2019, North Korea tested two projectiles that analysts believe were fired from a super-large multiple rocket launcher (MRL). Given that South Korea’s capital is located only about 50 kilometers from the Demilitarized Zone (DMZ), Seoul has long been under the threat of North Korea’s long-range artillery, short-range ballistic missiles, and upgraded MRLs. This latest test came nearly two years after North Korea’s Hwasong-15 ICBM test on December 1, 2017, nearly at the end of Trump’s first year in office and six months into Moon’s presidential term.

After one of North Korea’s MRL tests, the South Korean National Security Council released a statement on September 10, 2019, that said “we express our deep concern that North Korea continues to test short range projectiles since last May and we are reviewing the Korean Peninsula’s comprehensive military security situation.”18 For the first time in two years, the Ministry of National Defense acknowledged that “North Korea’s actions don’t help tension reduction on the Korean Peninsula” and “our military expresses deep regrets and call again on North Korea to cede all provocative actions.”19 While the Ministry of National Defense’s words were amply justified, the fact that the South Korean military waited so long to protest North Korea’s deliberate military provocations demonstrated the Moon government’s penultimate priority: fostering South-North engagement virtually regardless of North Korean actions.

A small but not insignificant domestic dustup captured the prevailing mood in Seoul. In August 2015, ROK Army Staff Sergeant Ha Jae-hyun lost both his legs to a North Korean mine while on patrol along the DMZ. Initially, when he was honorably discharged, Ha was designated as a “wounded warrior” for injuries stemming from war or combat-like duties. In September 2019, however, the South Korean Veterans Administration ruled that Ha was not a wounded warrior after all. It soon came out that the Veterans Administration’s Moon-appointed director believed that Ha should not receive such a designation because doing so would somehow, unbelievably, damage inter-Korean ties. In the end, Moon corrected the mistake with a presidential directive but only after massive public pushback.

Ha’s case illustrates just how politicized South Korea’s national security space is today. That an on-duty ROK military hero should have to ask the Veterans Administration to reinstate his status as a wounded warrior after he lost his legs to a North Korean land mine speaks volumes about the extent to which Moon administration officials are willing to forsake South Korea’s national security interests in the name of preserving a Sisyphean peace with the North. Such a development has been amplified by Trump’s egregious attempts to whitewash North Korea’s increasing nuclear and missile threats while arguing that U.S.-ROK combined military exercises are a waste of money and threatening to North Korea.

How much time Trump actually spends reading critical intelligence assessments and, more importantly, the insights he gains from looking at various situation reports remains unknown. But based on his cavalier remarks on a range of national security issues, denigration of his senior military and intelligence personnel, and impatience with policy experts, it remains highly unlikely that Trump has devoted any meaningful attention to why ROK and U.S. forces need to maintain very high interoperability standards through constant exercises. Since the 2016 presidential campaign and well into his first term, Trump has stated more contradictory positions on the Korean Peninsula than any of his predecessors. From talking loosely about why Japan and South Korea could have their own nuclear weapons, constantly attacking the strategic rationale for maintaining U.S. forces in South Korea and Japan, and his bromance with Kim, Trump has been instrumental in diluting the case for preserving and strengthening alliances with key allies such as Seoul and Tokyo.

The Dangers of a Hollowed-Out Alliance

Although Seoul and Washington continue to stress the rock-solid nature of the alliance, the Trump and Moon administrations have weakened alliance cohesion and deemphasized threat perceptions vis-à-vis North Korea. Whereas the readouts of previous top-level U.S.-ROK meetings on North Korea’s nuclear program clearly acknowledged the scale of the threat, more recent statements under Trump and Moon’s tenure have implausibly downplayed the risks.

The Trump and Moon administrations have weakened alliance cohesion and deemphasized threat perceptions vis-à-vis North Korea.

Early on, joint diplomatic statements released by the two administrations largely adopted language like that in previous documents. Other than ad-hoc meetings between ROK and U.S. presidents, one notable occasion for such pronouncements is the annual Security Consultative Meeting (SCM), the highest-level defense dialogue between Seoul and Washington. When the Trump and Moon administrations held their first SCM in Seoul in October 2017, the joint communique reaffirmed the United States’ commitment to South Korea’s defense following an unparalleled spike in North Korean provocations, including the country’s first hydrogen bomb test in September 2017. One of the 2017 document’s most poignant sections read:

The Secretary reiterated the longstanding U.S. policy that any attack on the United States or its allies will be defeated, and any use of nuclear weapons will be met with a response that is both effective and overwhelming. . . . The Minister and the Secretary committed to ensuring that extended deterrence for the ROK remains credible, capable, and enduring by continuing to enhance Alliance deterrence measures and capabilities in response to the increasing North Korean nuclear, weapons of mass destruction . . . , and ballistic missile threat, and continuing to promote information-sharing and interoperability.20

Exactly a year later, when the fiftieth SCM was held in Washington, DC, the 2018 joint communique highlighted the importance of inter-Korean détente. In the spirit of inter-Korean reconciliation that Moon was spearheading and Trump was cheering on, the 2018 document highlighted “various confidence building measures the ROK is undertaking with DPRK military authorities” and judged “that such efforts have had a positive influence on easing tensions on the Korean Peninsula.”21 To be sure, the South Korean defense minister also stressed that Seoul would continue to develop robust capabilities for repelling a possible North Korean invasion including key military cooperation with the United States.22 Nevertheless, the Ministry of National Defense has also been extremely cautious in assessing an array of threats from the North given the importance it currently attaches to inter-Korean CBMs despite the absence of any structural change in North Korea’s force deployments or military spending (see figure 1).

In June 2019, during the eighteenth Shangri-La Dialogue in Singapore sponsored by the International Institute for Strategic Studies, South Korean Minister of Defense Jeong Kyong-doo remarked, “With the three inter-Korean summits and two US-North Korean summits serving as a turning point, the security situation of the Korean Peninsula is undergoing dynamic changes towards solving the North Korean nuclear threat, boosting confidence and easing tensions between the two Koreas.”23 He went on to say:

Since the Moon administration set sail, however, the Republic of Korea has been able to find a ray of hope within the seemingly insurmountable clouds of war by improving inter-Korean relations and pursuing diplomatic solutions aimed at solving the nuclear threat. Now the Republic of Korea is facing a watershed point that will echo throughout our 5,000-year-long history. Our grand journey, while laden with difficulties for the establishment of permanent peace on the Korean Peninsula, has begun. . . . The Republic of Korea government has named a new order of peace and coexistence and also of cooperation and prosperity, to be generated through the complete denuclearisation and establishment of the permanent peace in the peninsula. . . . The new Korean Peninsula regime seeks to be a peace-cooperating community, moving from war and conflict to peace and coexistence, and an economic cooperation community moving away from ideological camps to economic prosperity.24

Although the minister’s bullishness on forging a permanent peace on the Korean Peninsula is understandable, given the inordinate amount of attention the government is paying to making peace with North Korea, it was remarkable that virtually nothing was said about North Korea’s ongoing work on nuclear weapons and other weapons of mass destruction.

For the Moon administration, the most ambitious and important item on the security agenda is imposing a peace regime on the Korean Peninsula that would supersede all other security and defense mechanisms. Such a strategy needs to be pursued carefully given the pushback from conservative South Korean politicians and voters on any significant diminution of the ROK-U.S. alliance. Still, the Moon government is betting that, because it was building on three inter-Korean summits in 2018 and emphasizing a significant reduction in inter-Korean tensions, the public would support sustained rapprochement, including the incremental restructuring of USFK and ROK-U.S. military cooperation.

Seoul wants to sign a permanent peace treaty to formally end the Korean War as soon as possible, while the United States, up until now, has said that related issues such as the future status of U.S. forces have to be ironed out in advance. Of course, Trump’s constant tirades that South Korea and other wealthy U.S. allies are taking the United States for a ride and Trump’s threats to pull U.S. forces out suggest that he would be supportive of an early signing of a peace treaty to replace the armistice. However, all the key U.S. national security departments including the Department of Defense and the Department of State, the U.S. Congress, and the U.S. military are against any hasty reduction of the USFK troop presence that could lead to a security vacuum.

For the Moon government, one of the most urgent national security issues is ensuring the full transfer of wartime operational control (OPCON) back to the ROK. As a sovereign state, South Korea has every right to maintain full OPCON over its forces. Washington and Seoul have agreed to expedite the transfer of conditions-based OPCON, which is seen by South Korean progressives as a major milestone in achieving greater defense autonomy. One of the main rationales for an accelerated OPCON transfer is the belief that doing so could improve inter-Korean military ties owing to a reduced role of USFK. But it remains highly unlikely that North Korea’s overarching military posture toward the South will soften when OPCON is transferred.

To counter criticisms from the right that the Moon administration has neglected South Korea’s defense modernization for inter-Korean détente, the Moon government has increased real defense spending in conjunction with its peace initiatives toward North Korea. Despite growing skepticism over the possibility of a groundbreaking U.S.–North Korea nuclear deal, the Moon administration continues to hope that as long as Trump remains focused on becoming the U.S. president who will bring lasting peace to the Korean Peninsula and as long as Seoul maintains its commitment to détente, Kim will eventually change course and make concessions in a bid for peace.

Whether that happens or not, the budget increase has been considerable. Regardless of how South-North ties evolve in the remaining two years of the Moon administration, defense officials point out that South Korea’s defense spending stood at $43 billion in 2018, a 7 percent increase over 2017 and the largest single-year increase since 2009.25 The South Korean Ministry of National Defense also announced that it was going to build a light aircraft carrier and that, overall, it plans to spend $239 billion more on defense from 2020 to 2024.

Military analysts in Seoul assert that while Moon’s defense budget increase is a positive development, it is also being spurred by other factors. As Reuters correctly reported, “While the surge in military spending may seem to contradict Moon’s push to engage North Korea, analysts say it is largely driven by other issues, including South Korea’s changing demographics and the country’s relationship with longtime ally the United States.”26 Other than demographic drivers, the array of South Korean platforms and weapons systems that need to be upgraded or replaced has increased significantly as the ROK military transitions to a more technology-based force. By increasing the defense budget, the government has also been able to increasingly satisfy the service’s procurement wish lists.

A Costly Debate on Cost-Sharing

Cost-sharing has become a major point of tension for the alliance under the Trump administration. In November 2019, negotiations between Seoul and Washington over a new Special Measures Agreement to cover the costs of U.S. troops based in South Korea broke down. James DeHart, the chief U.S. negotiator, said that South Korea “was not responsive to our request for fair and equitable burden sharing.”27 In 2019, South Korea paid roughly $920 million in direct costs toward stationing U.S. forces in South Korea. Multiple media outlets have reported that the Trump administration demanded that Seoul pony up $5 billion next year, a more than 400 percent increase.28 But Seoul also covers other costs, including by providing rent-free land for U.S. bases and by shouldering more than 90 percent of the nearly $11 billion cost of relocating most U.S. military personnel in South Korea to Camp Humphreys in Pyeongtaek.29 Additionally, South Korea already allocates around 2.5 percent of its gross domestic product for defense spending and is one of the largest buyers of U.S. weapons (see figure 2). According to a 2019 South Korean government report, from 2014 to 2018, South Korea imported $6.2 billion in arms from the United States, the fourth largest total worldwide.30 It goes without saying that South Korea still faces a nuclear-armed North Korea.

Nevertheless, since the 2016 campaign, Trump has operated under the mistaken belief that the United States pays an enormous amount to defend South Korea but receives virtually nothing in return. From a purely transactional point of view, South Korea’s direct contributions to U.S. defense is limited, but this is natural given that the United States is a superpower with global interests. Nearly twenty years into the War on Terror, the United States has spent hundreds of billions of dollars and has endured significant combat casualties, so it is understandable that Washington wants its key allies to assume a bigger share of the common defense burden. Unlike most European members of the North Atlantic Treaty Organization (NATO), South Korea has not receded from its core defense responsibilities. During the Vietnam War, the largest contingent of allied forces in South Vietnam other than U.S. forces were South Korean troops who fought alongside their American counterparts.31 South Korea contributes to U.S. interests by being a key political, economic, and military ally and by helping to maintain a strategic balance in Northeast Asia favorable to the United States.

Trump has taken a similar tact with other key U.S. partners. Throughout the 2016 U.S. presidential campaign, he focused his ire on South Korea (and to lesser extent other important U.S. allies and partners like Germany, Japan, and Saudi Arabia) for supposedly being “free riders” on defense. According to a November 2019 Foreign Policy article, then national security adviser John Bolton told his Japanese counterpart that Trump wanted a 300 percent increase in common defense costs from $2 billion to $8 billion, a hike comparable to the one Washington demanded of Seoul.32

By all indications, Trump’s stance on cost-sharing is deeply held. In a book based on discussions with former secretary of defense James Mattis who resigned in early 2018, Trump “wasn’t just grumbling publicly” about the high expenses of maintaining alliances but also “challenge[d] their value in private . . . asking [advisers] whether we could withdraw forces from . . . Japan, South Korea, and Germany.”33 According to conversations with former administration insiders, officials like Mattis and secretary of state Rex Tillerson tried unsuccessfully to convince Trump to tone down his jabs at key allies. Trump reportedly has his own idiosyncratic method of calculation that has convinced him that South Korea was ripping off the United States even more so than other U.S. partners.34 This may, in part, explain why Trump is fixated on teaching Seoul a lesson since, in his mind, such a rich and capable country should pay far more for stationing U.S. forces. Trump told Mattis that “it’s a losing deal! If [South Korea] paid us $60 billion a year to keep our troops overseas, then it’s an okay deal.”35

For the past several years, the United States has implemented a rotational force concept whereby U.S. forces are sent on short-term deployments. The Pentagon plans to implement division-strength rotations including the “South China Sea and surrounding areas, all in an effort to expand the Army’s presence in containing a resurging China and multiply forces in a hard-to-reach area.”36 According to press reports, Washington wants South Korea to shoulder the costs for relocating U.S. forces to and from South Korea in addition to sharing the cost for deploying strategic assets such as aircraft carriers and strategic bombers to the ROK. One of the reasons why Seoul has balked at assuming the cost of rotating U.S. forces is that it would mean paying for out-of-area deployment expenses. It would also weaken the argument that USFK is deployed in South Korea to deter North Korea rather than assuming more regional missions such as deterring Chinese forces. Moreover, such a move would also significantly decrease any support in the National Assembly for increasing South Korea’s share of common defense costs.

The Moon administration has largely stuck to a diplomatic script on cost-sharing negotiations since Seoul does not want to antagonize Trump at a delicate time for U.S.–North Korea relations. Neither Moon nor any of his senior officials have overtly criticized Trump’s outrageous demands given that Seoul still wants Trump to conclude a pathbreaking nuclear deal with Kim. When negotiations continued to stall, the South Korean foreign ministry said that “the two sides broadened their mutual understanding and consensus but confirmed that there are still differences between them.”37

Notwithstanding strong bipartisan support in the U.S. Congress in favor of the ROK-U.S. alliance and solid opposition to any sudden reduction of U.S. forces, if Trump does not get his way on defense costs, he may threaten to partially reduce USFK. That said, there are limits to how far Trump could go, given that Congress mandated that the secretary of defense certify that any significant reduction of U.S. troops in South Korea is necessary for U.S. national defense.38 As mentioned above, in December 2019, Congress reaffirmed its pledge to maintain the current level of 28,500 U.S. troops in South Korea.

Trump’s constant remarks about rich allies exploiting the United States may serve to embolden his “America First” message to his political base, but it certainly does not apply to Japan or South Korea. In an era of rapidly expanding Chinese military power and fluctuating U.S. influence in the Indo-Pacific, it makes even more sense for the United States to strengthen its ties with key allies. Indeed, one of biggest strategic assets the United States has, unlike China, is treaty allies throughout the Indo-Pacific that complement the U.S. political, economic, and military presence in the region. At the same time, it is incumbent on Washington’s allies to shoulder a fairer share of common defense costs in addition to increasing their respective defense budgets. Ironically, this is precisely what Japan and South Korea have done over the past several years.

Calculations about the worthiness of allies cannot be made primarily on the basis of dollar-for-dollar considerations. But even if one did consider the value of allies in more transactional terms, it is important to bear in mind that major U.S. allies such as South Korea and Japan are also two of the largest importers of U.S. arms—a major boost for the Pentagon and the U.S. defense industry. Contrary to Trump’s criticisms, rich U.S. allies in Asia are not defense free riders but key partners in a common defense grid that enhances U.S. influence.

Soul-Searching for Stable, Long-Term Security

For more than seventy years, the U.S.-ROK alliance has stood out as one of the most successful alliances forged after World War II. All alliances are affected by changing political and military circumstances, a reality evinced by the NATO enlargement that occurred with the end of the Cold War. The U.S.-ROK alliance has not remained immune to change and modernization. Yet the alliance faces unprecedented challenges going into the 2020s including the potent combination of unchanging military and political realities in North Korea; political leaders in Seoul and Washington with contrasting political goals vis-à-vis Pyongyang; bifurcated threat perceptions on North Korea; and a loss of readiness owing to canceled, truncated, or postponed U.S.-ROK exercises.

Trump has compelled South Korea to think hard about its long-term defense choices and strategy.

Trump has compelled South Korea to think hard about its long-term defense choices and strategy. There is no denying that the United States remains South Korea’s most important ally. Seoul continues to rely heavily on Washington for strategic intelligence and advanced combat aircraft such as the F-35. But Trump’s antics are prompting Seoul to do more to hedge its bets, including by expanding its own domestic arms industry. As one journalist has put it, “For now South Korea is still shopping American . . . [but] the frustration with needing to pay up in order to catch up has helped push forward the idea of South Korea’s military becoming more self-reliant.”39 And, admittedly, there are sound strategic and political reasons for South Korea to become more self-sufficient on the defense front. South Korea’s advanced industrial base and desire to lessen its technological dependence on the United States resulted in the development of the KF-X, an indigenous fighter jet, in addition to next-generation cruise missiles and long-range ballistic missiles.

As one of Asia’s largest economies and a major military player, South Korea is rightly seeking greater defense autonomy provided that such steps enhance and strengthen the country’s core defense posture and national security interests. But as Seoul calibrates its long-term defense needs and security paradigm, it is fitting for the ROK to remind itself of the opportunity costs associated with intensified nationalistic considerations versus more realistic security assessments. Should Seoul feel that it is time to assume a more independent defense posture, then it follows that South Korea must be absolutely willing and able to bear significantly higher defense costs. Meanwhile, South Korea should assume wartime OPCON as soon as conditions permit it to do so. However, it is critical to understand that enhanced autonomy means that South Korea has to make immense investments in strategic intelligence, modernized command and control infrastructure, more secure supply chains, and robust defense R&D. Absent such real efforts, South Korea’s defense posture cannot but inexorably weaken.

The major tasks for South Korea are balancing the understandable desire for greater security autonomy, maximizing its defense capabilities vis-à-vis a nuclearized North Korea in conjunction with the United States, minimizing growing political and military pressures from China, and managing its brittle but critical relationship with Japan. Even under the best of circumstances, such undertakings will require immense strategic foresight and political acumen. It is also crucial for South Korea to understand that Chinese military might and political power is higher than at any point in recent decades and is continuing to grow with each passing year. Absent a fundamentally strong alliance with the United States and shared security perceptions between Seoul, Tokyo, and Washington, South Korea has to ponder what leverage it has in relation to an increasingly powerful and assertive China.

At a time when China is flexing its military muscle as never before, it behooves the United States to nurture and sustain the closest of ties with core allies and partners in the Indo-Pacific. Treaty allies like Australia, Japan, South Korea, Thailand, and the Philippines are a comparative advantage that a rising China or an irredentist Russia simply do not have. South Korea is an important and valuable ally not because it provides equal protection for the United States but because it plays an indispensable role in helping to maintain a regional balance that coincides with U.S. interests and strengthens U.S. regional standing. As a superpower, the United States can opt to go it alone while extricating itself from both Asia and Europe. The moment it does so, however, would also signal the beginning of the end of U.S. supremacy.

About the Author

Chung Min Lee is a senior fellow in the Asia Program at the Carnegie Endowment for International Peace. Prior to joining Carnegie, he taught for twenty years at the Graduate School of International Studies at Yonsei University in Seoul. Lee is chairman of the International Advisory Council of the International Institute for Strategic Studies. From 2013 to 2016, he served as ambassador for national security affairs for South Korea and from 2010 to 2011 as ambassador for international security affairs.


1 Simon Denyer, “North Korea Announces Test of New Type of Submarine-Launched Ballistic Missile,” Washington Post, October 2, 2019,

2 South Korean Ministry of National Defense, 2018 Defense White Paper (Seoul: Ministry of National Defense, 2019),

3 Hayes Brown, “North Korea’s Missile Tests,” BuzzFeed News, September 9, 2019,

4 David E. Sanger and William J. Broad, “North Korea Missile Tests, ‘Very Standard’ to Trump, Show Signs of Advancing Arsenal,” New York Times, September 2, 2019,

5 U.S. House of Representatives, 116th Congress, National Defense Authorization Act for Fiscal Year 2020, December 9, 2019,

6 Ibid.

7 “Kim Jong Un’s 2019 New Year Address,” National Committee on North Korea, January 1, 2019,

8 “2019 Moon Jae-in Daetongryeong shinyeongija hoekyeon—Daehanminguk saeroeun 100nyeon hamkae jalsaneun nara,” [President Moon Jae-in’s 2019 New Year’s Press Conference: A New 100 Years for the Republic of Korea, A Country Where Everyone Lives Well], the Blue House, January 10, 2019,

9 South Korean Ministry of National Defense, 2016 Defense White Paper (Seoul: Ministry of National Defense, 2017),

10 South Korean Ministry of National Defense, 2018 Defense White Paper.

11 Ibid., 297.

12 Choe Sang-hun, “North Korea Says It Has Tested ‘Ultramodern Tactical Weapon,’” New York Times, November 15, 2018,

13 “The CNS North Korea Missile Test Database,” James Martin Center for Nonproliferation Studies, December 3, 2019,

14 “North Korea Tests Submarine-Capable Missile Fired From Sea,” BBC, October 3, 2019,; and “North Korea’s New SLBM: The Pukguksong-3,” Arms Control Wonk [podcast], October 8, 2019,

15 Elias Groll, “North Korean Missiles Just Keep Getting Better,” Foreign Policy, October 3, 2019,

16 “Pukguksong-2 (KN-26),” Center for Strategic and International Studies (CSIS), Missile Threat: CSIS Missile Defense Project, October 7, 2019,

17 Ibid.

18 “Nambukgwangwe juyoilji 2019nyeon 9wol,” [Major Events in South-North Relations, September 2019], South Korean Ministry of Unification, October 4, 2019,

19 Yun Hee-hoon, “Gun, Bukbalsachae dobalae ‘ganghan yugam’ 2nyeonmanae cheot gongshik seongyeong…’innae jeolryak’ seonhwehana,” [Military announces first formal statement of ‘deep regret’ in 2 years . . . Does this mean a shift in the ‘patient strategy?], Chosun Ilbo, November 28, 2019,

20 “Full Text of ROK-U.S. Security Consultative Meeting Joint Communique,” Yonhap News Agency, October 28, 2017,

21 “Joint Communique of 50th U.S.-ROK Security Consultative Meeting,” United States Forces Korea, October 31, 2018,

22 Ibid.

23 “Speech by Jeong Kyong-doo, Minister of National Defense, Republic of Korea,” Eighteenth Asia Security Summit, the IISS Shangri-La Dialogue, Second Plenary Session, Saturday, June 1, 2019, 2,

24 Ibid., 4–5.

25 Josh Smith, “Buying a Big Stick: South Korea’s Military Spending Has North Korea Worried,” Reuters, September 11, 2019,

26 Ibid.

27 Min Joo Kim, “US Breaks Off Talks With South Korea Over Costs of Military Alliance,” Washington Post, November 19, 2019,; Andrew Jeong, “South Korea to Pay More Under New Military Deal With U.S.,” Wall Street Journal, February 10, 2019,

28 Lara Seligman and Robbie Gramer, “Trump Presses Japan to Pay Up for U.S. Troops,” Foreign Policy, November 18, 2019,

29 Kim, “US Breaks Off Talks With South Korea Over Costs of Military Alliance.”

30 Elizabeth Shim, “South Korea a Top Buyer of U.S. Weapons, Annual Report Says,” United Press International, December 16, 2019,;

31 Glenn Baek, “A Perspective on Korea’s Participation in the Vietnam War,” Asan Institute for Policy Studies, Issue Brief 53, April 9, 2013,

32 Lara Seligman and Robbie Gramer, “Trump Asks Tokyo to Quadruple Payments for U.S. Troops in Japan,” Foreign Policy, November 15, 2019,

33 Guy Snondgrass, Holding the Line: Inside Trump’s Pentagon With Secretary Mattis (New York: Penguin Random House, 2019), Kindle edition, 62.

34 Ibid., 66.

35 Ibid., 169.

36 Todd South, “The Pacific Push: New Rotation, Thousands More Soldiers Headed to the Region as the Army Readies for a New Kind of Fight,” Army Times, May 8, 2019,

37 Kim So-hyun, “S. Korea, US Still Have Differences on Defense Cost Sharing: Ministry,” Korea Herald, January 16, 2020,

38 Catie Edmondson, “Senate Rebukes Trump Over Troop Withdrawals From Syria and Afghanistan,” New York Times, January 31, 2019,

39 Morten Soendergaard Larsen, “Tired of U.S. Dependence, South Korea Seeks to Build—and Sell—Its Own Weapons,” Foreign Policy, November 1, 2019,