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Although they share a common ally, history and politics keep Japan and South Korea at arm’s length and severely limit their defense cooperation. Since at least the mid-1990s, American realists—and not a few Japanese and South Korean analysts—have anticipated that the regional environment, growing steadily more dangerous, would bring these status quo democracies closer together, not least because Washington would drive them to cooperate. Moreover, since Japan has not contended for regional hegemony and since its defense budget has not increased as fast as China’s, South Korea ought to be reassured and feel less threatened. Indeed, although Seoul sees Beijing as a critical (if often unhelpful) intermediary in peninsular affairs, China poses clear challenges for both it and Tokyo. North Korea and the remarkably rapid development of its WMD capabilities pose an unambiguous threat to both of America’s Northeast Asian allies. South Korean President Roh Moo-hyun and Japanese Prime Minister Koizumi Junichirō agreed to meet annually in 2004, but Koizumi’s visits to the Yasukuni Shrine forced Seoul to take this off the table. The meetings were back on when Lee Myung-bak took office, but canceled again by Park Geun-hye.¹ Washington has pressed them to cooperate, but only with intermittent success.

The stakes of security cooperation for South Korea, Japan, and the United States are high. In the event of a North Korean missile attack, smooth and seamless data sharing could, for example, greatly increase missile intercept probabilities. Should a general war recur on the peninsula, Japan could, if permitted, bring a range of important military and civil defense capabilities, some of which would otherwise be in very short supply. Whether or not third-country civilians can be smoothly and efficiently evacuated largely depends on mutual planning and cooperation, and given the logjam that could occur should a “noncombatant evacuation operation” (NEO) fail, the ROK has as much interest in this as Japan does. From a broader perspective, Japan-ROK cooperation will influence the willingness of US citizens to support the defense of America’s two most important East Asian allies. Yet despite many material incentives, cooperation today disappoints. As we approach the 20th anniversary in October 2018 of the comprehensive “New Japan-Republic of Korea Partnership towards the Twenty-first Century” signed by President Kim Dae-jung and Prime Minister Obuchi Keizō, this has been a decades-long story of two steps forward and 1.5 steps back, filled with diplomatic one-upmanship and derailed agreements.²   

In this essay, we briefly assess the record of security cooperation since North Korea’s 2006 nuclear test and how the discontinuation of the Six-Party Talks in 2009 highlighted the growing gravity of the threat. We then examine several areas of underperformance, and close by recommending measures that may, at the margins, improve the prospects for meaningful cooperation.

The Diplomatic and Political Context

The detection of North Korean nuclear weapons program in 1993 and the Agreed Framework the following year set the stage for intensified, if still informal, trilateral coordination on political and security affairs. Those efforts received an enormous boost when Kim Dae-jung visited Japan in October 1998 and agreed with Obuchi Keizō that Japan and South Korea should upgrade their political, security, and economic relations, on the understanding that Japan would more forthrightly confront its imperial history. Their joint declaration cleared the way for a number of defense exchanges and the installation of hotlines between the military establishments.³ The two navies engaged in search and rescue exercises, and there was some discussion of intelligence sharing. The agreement also enabled the formalization of US-ROK-Japan discussions about their approach to North Korea, under the Trilateral Coordination and Oversight Group (TCOG).⁴

During the second half of Kim’s tenure, further progress was hampered by domestic opposition, especially after Koizumi’s August 2001 Yasukuni visit. Roh Moo-hyun was elected in 2003, largely on the basis of an anti-American platform that left little space for improving relations with Japan. Roh continued Kim’s Sunshine Policy towards North Korea, while also asserting a far more independent course. He was determined that South Korea should play a “balancer” role within the region between China and Japan—by, in effect, tilting towards China—and build a “self-reliant defense capability.” The Six-Party Talks, initiated in August 2003, brought North Korea to the negotiating table but at some cost to trilateral coordination. TCOG meetings continued for a time, but only informally, at lower levels, and without generating actionable recommendations.⁵ Events in Japan, including the adoption in 2005 of new textbooks that downplayed Japanese wartime misbehavior and Koizumi’s sixth visit to Yasukuni (and the first on the politically sensitive August 15 anniversary of Japan’s surrender), led Roh to declare his readiness for a “diplomatic war” with Japan.⁶ 

The election of the more pragmatic business leader and local politician, Lee Myung-bak, in December 2007 coincided with the tenure of the moderate Fukuda Yasuo and raised the prospects for better relations with both Washington and Tokyo.⁷ During Lee’s first visit to Tokyo in April 2008, Prime Minister Fukuda expressed the hope that under Lee’s leadership Japan and ROK would establish a “mature partnership…the closest ever” and that the trilateral relationship among Washington, Tokyo, and Seoul would be “coordinate[d] more closely than ever before.”⁸ Lee visited Tokyo seven times while in office, but warmer relations with Tokyo were contested from the beginning.⁹ Political opposition to thawed relations with Japan played out against a backdrop of frustration over the impasse with Pyongyong. North Korea withdrew from the Six-Party Talks in 2009, after condemnation by the other five parties of a North Korean rocket launch.  

One more blow to relations came after the collapse of impending security agreements. In January 2011, Japanese and South Korean defense ministers began pursuing negotiations on intelligence sharing and logistical cooperation. A bilateral General Security of Military Information Agreement (GSOMIA) was prepared for signing in July 2012. But in June, under media and political criticism for the lack of public hearings and transparency, Lee canceled the scheduled signing of a “direct and comprehensive” bilateral GSOMIA with Japan at the eleventh hour.¹⁰ In August, in an attempt to reclaim political control, Lee invoked the issue of wartime “sexual slavery”—what the Japanese refer to as the “comfort women” issue—and flew to the disputed Dokdo/Takeshima Islands, leading Tokyo to withdraw its ambassador and file a protest. Lee again reversed himself by declaring that the Japanese emperor would not be welcome in South Korea until he issues an apology for Japan’s 20th century colonialization of Korea. 

The administration of conservative Park Geun-hye followed the same trajectory of foreign policy hope and disappointment. Her election in December 2012 was met with cautious optimism in Washington and Tokyo. Park had promised a policy of “trustpolitik” toward Pyongyang, but also an enhanced alliance with the United States and a new start for trilateral relations among Washington, Seoul, and Tokyo.¹¹ But her “Seoul Process” was tested even before her inauguration, when North Korea launched an Unha-3 rocket, and soon thereafter when it conducted its third underground nuclear test. Six rounds of bilateral talks did nothing to slow North Korea’s missile and nuclear weapons programs.¹²

Although Park first visited Washington soon after her election in May 2013, the first bilateral summit between Park and the newly elected Prime Minister Abe was not held until November 2015, and she never visited Tokyo.¹³ This meeting was met with optimism on the Japanese side and was followed with a December 2015 agreement on the “comfort women” issue in which Japan agreed to create a fund to support the surviving women and (according to Japanese sources) South Korea promised it “will strive to resolve” Japan’s objections to a “comfort women” statue in front of its embassy in Seoul in consultation with civil society groups. Despite being touted as having “resolved [the issue] finally and irrevocably,” it came unglued less than two years later.¹⁴  

Park’s successor, Moon Jae-in, had pledged its renegotiation during his election campaign at a turbulent period of domestic politics that included the arrests on corruption charges of Park as well as of her chief of staff, Lee Byung-kee, a former ambassador to Japan and the architect of the “comfort women” deal. Japan had paid ¥1 billion in 2016 to the fund, but Moon, responding to public outcry, met with former “comfort women” and announced that there were “grave flaws in the procedure and content.”¹⁵ Tokyo issued a formal protest and Abe, disappointed with Moon’s attempt to “move the goalposts,” insisted that “the agreement will not budge, not even by a millimeter.”¹⁶ Moon eventually announced he would not seek renegotiation, but insisted that Japan “recognize truth and offer a sincere apology” to the victims.¹⁷  

ROK-Japan Security Cooperation

The deterioration in ROK-Japan relations during this period had repercussions for four issues in the military domain as well—intelligence sharing, noncombatant evacuation operations, logistical cooperation, and joint training. Here we address each briefly in turn: 

1) Intelligence Sharing. After Japan signed a GSOMIA agreement with the United States in 2007, it concluded similar agreements with France, Australia, the United Kingdom, and other aligned states. But agreement was most difficult to reach with the ROK. After Lee canceled a bilateral GSOMIA, Washington stepped in to persuade its East Asian allies to try a different approach in December 2014.¹⁸ To avoid having to deal with one another directly, Seoul and Tokyo would channel a video conferencing link through the Pentagon to share intelligence regarding North Korean nuclear and missile testing. Even the agreements to set up this contrivance were initialed separately with the United States by each country.

The December 2015 “breakthrough” on the “comfort women” issue converged with escalating provocations by Pyongyang—including its fourth nuclear test— and paved the way to renewed discussion of a bilateral GSOMIA. South Korea and Japan seemed to acknowledge (at least to themselves) that their “by-pass” was dangerously inefficient, as Washington ratcheted up pressure—including whispers that the US-ROK agreement on THAAD deployment was at risk. The South Korean government announced in January 2016 that it would establish a new military data link to share text and satellite imagery on the DPRK nuclear program with US Forces Korea (USFK). It did so knowing that this would effectively connect with US Forces Japan (USFJ) and, thereby, to the Japanese SDF with its own direct link to USFJ.¹⁹ There were, however, important limitations. Passing the information provided to third parties (including the United States) would require written permission in advance.²⁰

In early February 2016, ROK defense minister Han Min-Koo’s testimony in Parliament that the government was considering reopening GSOMIA talks with Japan was met with vigorous opposition. Han quickly backed off, saying that he meant simply that “various factors should be taken into consideration before a GSOMIA deal could be reached.” ²¹ Apparently they were, for Japan’s defense minister, Nakatani Gen, took up the dormant GSOMIA issue at a meeting in April with Park Geun-hye.²² This overture was met with official support. Han now declared that a bilateral GSOMIA “is necessary from a military perspective.”²³ But it was not until Pyongyang’s fifth nuclear test in September that Korea’s Ministry of Defense called upon the public to support a bilateral intelligence sharing agreement with Japan.²⁴ Soon thereafter, the ROK government announced it would resume GSOMIA talks with Japan. Washington welcomed the announcement, but in South Korea, the opposition began to get traction on the issue almost immediately. Under mounting pressure, the ministry was forced to insist that the shared intelligence would be limited to helping rescue Japanese residents in South Korea and would not include information about troop deployments. To appease the opposition, the (apparently desperate) government even proposed a GSOMIA to Beijing.²⁵ Still, all three opposition parties vowed to block the agreement and called for Han’s resignation.

While Park administration corruption scandals diverted attention, the bilateral GSOMIA—which did not require legislative ratification—was signed in November, just three weeks after the talks were restarted. The two militaries directly exchanged classified intelligence for the first time in mid-December 2016. Although long-term prospects for the agreement—the object of characteristically blistering attacks by North Korea—remained uncertain under Moon, it was extended for one year just before Pyongyang’s sixth nuclear test in August.²⁶ When the extension was signed, Seoul made clear it would limit sharing to intelligence regarding North Korean missile and nuclear programs, and refused requests from Japan for information about Chinese activities in the South China Sea.²⁷ Limits to intelligence sharing are mirrored in limited sharing regarding plans for noncombatant evacuation operations in the event of a contingency on the peninsula. 

2) Noncombatant Evacuation Operations. Japan has actively sought to coordinate with South Korea on preparation and approval for a military-assisted evacuation of its civilian nationals in the event of a conflict on the peninsula, with little to show for its efforts thus far. It is well understood that a military contingency on the Korean Peninsula could displace hundreds of thousands of people who will have limited options as they struggle to get out of harm’s way. At any one time, there are roughly 60,000 Japanese and almost 250,000 Americans in South Korea. Declaring an evacuation during peacetime could spark a war by conveying to North Korea that the United States and South Korea intended to attack—even if they had no such intention.²⁸ Hence, it is likely that no civilian movement aided or encouraged by national governments is likely to occur until war looks inevitable or, more likely, had already begun.

A mass evacuation during conflict would cause immense hardships and could easily turn into a humanitarian disaster. Foreign residents may be joined on the roads by millions of South Koreans fleeing the battle areas, clogging the transportation arteries moving south. At the same time, large ROK and US military forces would be moving north, further overloading the transportation system. Many civilians would be stuck on the roads, all confused, most without food, and some sick. Due to Korea’s geography and the demography of foreign residents, finding and caring for evacuees, much less moving them, would be an enormous logistical challenge, vastly greater than any faced by the United States and its partners in recent history. Under such circumstances, military support (with the logistical, communications, and organizational support that implies) would be essential, especially since civilian aircraft and ships would likely not be permitted to enter or exit.²⁹ 

Japan has taken a number of steps to facilitate deployment of the SDF in non-combatant evacuation operations (NEO). ASDF, MSDF, and GSDF assets (including a 50-member “guides” unit within the 1st Airborne Brigade) have been earmarked for NEO, and the SDF has practiced evacuation operations for Japanese civilians in Thailand and Djibouti. Japanese law was amended in 2015 to include support for what is called “Transportation of Japanese Nationals Overseas” (TJNO) to allow Japanese troops to use weapons while guarding, rescuing, and transporting civilians.³⁰ Japanese law allows, upon request from the Minister of Foreign Affairs, protection of Japanese civilians on the Korean Peninsula during a crisis to be ordered by the minister of defense in consultation with the minister of foreign affairs with the approval of the prime minister. Contingency plans for a Korea NEO reportedly include the dispatch of ground elements to assist with the movement of Japanese citizens from Seoul to Busan, and the use of MSDF ships to transport those individuals home.³¹

Any dispatch of SDF personnel or equipment would legally require the approval of the South Korean government, and the prospects at present appear dim. In October 2016, while negotiating GSOMIA, the ROK foreign minister insisted that South Korea would not provide the Japanese military with information about Korean ports, roads, or infrastructure during an evacuation. Still, he insisted that because Japan has more intelligence assets collecting data on North Korea, he expected Japan to provide information on North Korea’s nuclear weapons, missiles, and submarines. The Japanese government has sounded out South Korean officials about approval for the dispatch of the SDF elements, and the South Korean side has replied that they would decline, citing the sentiments of the public.³² Nor does the ROK government appear receptive to serious contingency planning with Japan.³³

Based on Japan’s strategic position as a logical way-point for virtually any non-Chinese evacuation of third-country citizens, Japan has a powerful bargaining position with partner states, virtually guaranteeing the assistance of others in evacuating Japanese nationals. Such assistance would start with the United States. Under the 2015 Guidelines on Defense Cooperation, the two agreed to assist one another in non-combatant evacuations. In November 2017, Defense Minister Onodera Itsunori and the commander of USFK, General Vincent Brooks affirmed US-Japan coordination in the event of a Korean contingency, including evacuation of Japanese nationals.³⁴ Yet Japanese officials are justified in pondering whether Japanese nationals would receive the same priority from overloaded US military personnel, even with the best of intentions, as they would from the SDF.

Finding and communicating with tens of thousands of Japanese civilians, many of whom speak only limited English, would be enormously difficult for US forces—and could result in significantly higher Japanese civilian casualties. Yet, the Japanese military is capable of delivering critically important non-combat capabilities, not only to rescue its own nationals, but also to help what may be as many as a quarter of a million allied ones. Not having forces on the peninsula and tasking the US military evacuate its civilians, Japan would strain US capabilities and distract them from other urgent military tasks. 

Although South Korea’s intransigence on an issue that would affect countless civilians, as well as peninsular security, is inexcusable, Japan’s overheated public discussion may distract from potential solutions. Rather than discussing the costs and specific measures that would save lives and reduce the stress, some Japanese politicians have warned that an NEO could be a pretext for infiltration of Japan by North Korean agents. Deputy Prime Minister Aso Tarō, for instance, has repeatedly mused in public about the possibility of having to shoot armed North Korean agents arriving amidst waves of refugees demanding sanctuary in Japan-based settlement camps: “Terrorism might occur. We have to prepare our government to deal with such a situation.”³⁵ Such fear mongering may limit the willingness of Japan to host any foreign nationals fleeing the war zone. 

3) Logistics Cooperation. With tensions high regarding Taiwan and North Korea, Washington and Tokyo strengthened arrangements for logistical cooperation in the September 1997 Guidelines for US-Japan Defense Cooperation by breaking with past practice and outlining Japanese logistical support for US forces in the event of contingencies in “areas surrounding Japan.” Tokyo and Washington also signed an Acquisition and Cross-Servicing Agreement (ACSA), one of dozens of such agreements Washington has reached with allies and partners worldwide. Under the terms of ACSA, the countries may rapidly transfer supplies as needed in exchange for reimbursement in cash, replacement in kind, or equal value exchange. Japan and South Korea each have an ACSA with the United States, but not with one another.

Given the centrality of events in Korea to Japanese security, Tokyo has sought to conclude an ACSA with the ROK since shortly after signing the US agreement. It was on Tokyo’s agenda following the Obuchi-Kim joint declaration and during negotiations on deepening security relations with the Lee government, but, like the GSOMIA, it was not signed.³⁶ With the acceleration of North Korean missile and nuclear programs, the United States and Japan signed new Guidelines for US-Japan Defense Cooperation in April 2015 that went beyond the 1997 Guidelines to specify that the two “will cooperate as appropriate with other countries taking action in response to armed attack.”³⁷

Signing an ACSA has taken on added urgency as preparation for a possible NEO from Korea has become more pressing. Not only might Japan be able to supply the ROK with critical materials more efficiently during a conflict, but Japanese units dispatched to the peninsula might also require the access to local materials (e.g., equipment to supplement communications, transportation, or relief supplies) that an ACSA might facilitate. In April 2015, the Nihon Keizai Shimbun reported that “Japan regards signing the ACSA as the biggest priority for security cooperation with South Korea.”³⁸ In October 2017, Asahi Shimbun reported that Japan had again advanced the need to negotiate an ACSA, but within a week, the South Korean defense ministry spokesman stated categorically that “at present, there is no discussion [of an ACSA], and there is no plan for concluding one.”³⁹

Nonetheless, there have been at least two cases of what might be called “proto-ACSA cooperation” between the Japanese and ROK militaries, both hampered by a politically unstable relationship.  The first concerned the F-35 fighter. In 2014, Japan and Australia were chosen as the maintenance and upgrade sites for the F-35 program in Asia, which includes repair, overhaul, and upgrade (MRO&U) work for ROK and Singaporean fighters.⁴⁰  No sooner had Japan been announced as the Northeast Asian hub, a South Korean defense procurement official announced, “There will never be a case where our fighter jets will be taken to Japan for maintenance.” “South Korea,” he continued, “has the right to decide where to conduct maintenance for the F-35 jets.”⁴¹ In the meantime, the ROK will send its aircraft to Australia for maintenance, despite warnings by US Air Force Lt. Gen. Christopher Bogdan that moving entire aircraft over the 7,000 miles between South Korea and Newcastle, Australia would be uneconomical, given the large fuel and support requirements—especially given that aircraft requiring depot maintenance often have compromised abilities to fly. ⁴²

The second occurred in in December 2013 in South Sudan where both nations’ militaries were serving as United Nations peacekeepers.  After a deputy commander of a South Korean unit requested assistance in the face of a sharp escalation of violence, the Abe government waived the then still extant ban on the export of arms for the first time and authorized Japanese peacekeepers to supply ammunition to South Korean troops.⁴³ Although the transfer was undertaken under UN procedures at the direct request of the South Korean officers, South Korean netizens and Japanese pacifists both protested ROK government encouragement of the revival of Japanese militarism.⁴⁴ The South Korean Defense Ministry quickly announced that it was shipping additional ammunition to its UN peacekeepers and would return the 10,000 rounds to the Japanese military.⁴⁵  

4) Combined Training. Combined training exercises have, in some ways, proceeded more smoothly (especially in a multilateral context) than cooperation in other security-related areas, though such exercises too have sometimes been affected by the political winds. In the wake of the Kim-Obuchi meetings, the Japanese Maritime SDF and ROK Navy held a search and rescue exercise in August 1999 and have continued to hold such exercises on a biennial basis since (most recently in December 2017).⁴⁶ Search and rescue exercises constitute the least controversial of combined training types and are often conducted by potential adversaries for confidence building. Despite the promising early start, bilateral exercises have not progressed beyond search and rescue, but the two have managed to expand their cooperation in multilateral exercises.

In 2008, Washington and its allies pledged to step up trilateral military exercises. In July 2010, Japan dispatched observers to the US-ROK Invincible Spirit exercise, and in December of the same year, South Korean observers attended the US-Japan Keen Edge exercise⁴⁷. The Japanese and ROK militaries have participated for years in a variety of US-sponsored multilateral exercises—such as RIMPAC and Red Flag. Recently, Japan and South Korea have leveraged such exercises to gain experience of direct collaboration. In 2013, the two US allies participated in the Red Flag exercise together for the first time, and South Korean F-15 fighter jets escorted a Japanese C-130 cargo plane, defending it from “a flurry of simulated attacks.”⁴⁸ By far the most important trilateral training events are the Pacific Dragon missile defense exercises, the first of which was held off the South Korean coast in June 2012⁴⁹. In June 2016, the third exercise was held off the Pacific Missile Range Facility in Kauai, Hawaii, and the participants reportedly “shared tactical data link information” in accordance with the intelligence sharing agreement⁵⁰. Notably, even this exercise was held months before the November 2016 signing of the GSOMIA. The pace of missile defense exercises has accelerated over the last year, with events held March, October, and December of 2017⁵¹.

Although the Pacific Dragon exercises are an important success story, they are a single exercise series dedicated to a specific military function, and do not represent a blanket acceptance of the need for trilateral exercises. In November 2017, the United States, the ROK, and Australia conducted trilateral exercises off Jeju Island, but Seoul declined to invite Japanese participation. Later in the month, three US aircraft carrier strike groups were available for exercises in Northeast Asia. A Japanese proposal for trilateral exercises was, however, rejected by Seoul, reportedly because of sensitivity to Chinese opposition. And the ROK government felt it necessary to specify that military cooperation with the Japanese and US militaries would not develop into an alliance.⁵²

Conclusion

A US military official told us, with full confidence, that “Japan-ROK historical enmity will dissolve when self-interest kicks in.”⁵³ But this is hardly certain, at least not within an acceptable timeframe. While the shifting balance of power in Northeast Asia ought to pull the ROK and Japan together, there clearly are other forces that keep them apart—even when viewed through a realist lens: the ROK and Japan have different perceptions of the China threat, they are engaged in latent security competition, they compete economically and technologically in the same markets, and a stubborn territorial dispute continues to stifle military cooperation. This should not be entirely surprising; a large and growing body of neoclassical realist scholarship convincingly demonstrates that, even under the best of circumstances, balancing is often imperfect and can be easily undermined.⁵⁴

There are, of course, non-material features that undermine the relationship, deriving from the unpleasant history of Japanese colonialism, and are manifest in endless manipulation of history by political entrepreneurs in both countries whose domestic gains generate bi- and trilateral costs. Too many Japanese textbooks have been written as if their authors wielded only erasers, and too many South Korean commentaries have been crafted to privilege victimization. Material factors and identity politics converge to frustrate intermittent efforts at lasting reconciliation.

Although South Korea and Japan have, for their own strategic reasons and in response to Washington’s urging, explored the idea of closer security cooperation for two decades, the outcome has been far from satisfactory for either side—or for their common security partner, the United States. Some progress has been made on confidence building measures, combined military exercises, and intelligence sharing, but the partial nature of this progress and the continuing limitations on it are more notable. No agreement on logistics has been reached, and forward progress appears entirely at a standstill. Intelligence sharing remains unsatisfactory, especially in the context of fast-moving missile warfare. Most perplexing in terms of the dangers to innocent civilians, discussion of NEO has, thus far, remained almost entirely off the table. Thus, Washington has felt compelled to intervene sporadically to bring its most valued allies in Northeast Asia to cooperate with one another. 

Even as they huddle beneath the penumbra of the North Korean nuclear threat, Japan and South Korea engage in unproductive diplomatic one-upmanship, as when President Trump visited Seoul in November 2017 to be embraced by a victim of “sexual slavery” and to be served “Dokdo” shrimp at what the Japanese press called “an anti-Japanese banquet.”⁵⁵ The unraveling of fraternal ties, such as they ever were, has expanded to the United States, where Osaka broke off longstanding sister-city relations with San Francisco after the latter installed a statue of three “comfort women” (Chinese, Korean, and Philippine) alongside one of Kim Hak-sun, the first to testify publicly about her experience.⁵⁶ Rhetorically, the three countries claim to be on the same page regarding the need to continue to press Pyongyang to abandon its nuclear and missile development programs, but Abe is reportedly concerned about Seoul’s plan to offer $8 million in humanitarian aid to North Korea, and Moon is concerned about Tokyo’s hard line toward the North.⁵⁷

What is to be done? We offer several recommendations in the full knowledge that the more ambitious of them are unlikely to be implemented and that, if effective at all, would not be a magic bullet. First, the United States should continue to provide venues and opportunities for military cooperation between its two allies. The Pacific Dragon exercise series and examples of Japan-ROK cooperation during multilateral exercises provide a rough guide for how military-to-military cooperation (and intelligence sharing) can be fostered through regularized but relatively low-profile exercises. US alliance managers should look for other areas in which functionally oriented exercises might be undertaken, as in the case of the proliferation security initiative. Additional opportunities for trilateral (or bilateral) activity might also be sought on the sidelines of larger, multilateral exercises. 

Second, Washington should refrain from pressing Tokyo and Seoul towards a “shortcut” to resolve thorny political issues. It can encourage deep reconciliation—and voice its own concerns—and US specialists can continue to play a role in regional dialogues. But pressuring South Korea or Japan to bury their differences quickly for instrumental purposes is likely to either prove ineffective or backfire. Due to the cross-cutting material and ideational pressures we have described, these efforts never succeed for long, as in the 2015 “comfort women” agreement, leaving neither side satisfied.

Third, Washington might attempt to stimulate deeper cooperation between Seoul and Tokyo by providing greater positive incentives for cooperation, e.g., pursue a robust “Three Eyes” intelligence arrangement with Tokyo and Seoul. Under such an arrangement, US security officials could map out a five- or ten-year plan that provides the phasing in of not only enhanced intelligence sharing, but also a range of other elements, such as employing ROK and Japanese officers in staff assignments within the US major commands—similar to positions currently held by members of the “Five Eyes.” To be sure, such a proposal would challenge long-held patterns of interaction, as well as the adaptive capabilities of all parties—and might prove impossible due to constitutional constraints in Japan or political sensitivities in South Korea. But US leaders should consider ways to adjust alliances in accordance with the place that Asia (and these states in particular) holds in US security and the enormous changes that have taken place over the last several decades.