Korea’s Geostrategy as an “In-Between State” in an Age of Geopolitical Competition: Concepts, Cases, and Options

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Bong-Geun JUN

Visiting Research Fellow, Sejong Institute

1. Introduction

With geopolitical conflict emerging worldwide as the greatest threat to security, Canadian Prime Minister Mark Carney addressed the World Economic Forum in Davos in January 2026 and warned of the fate awaiting small and middle powers: “if we're not at the table, we're on the menu.” Korea in particular cannot afford to ignore this warning, given that in an era of U.S.-China competition it is exposed simultaneously to the dual risk of entrapment and abandonment within the ROK-U.S. alliance. This is because the Korean Peninsula has historically been situated in a geopolitical seismic zone where continental and maritime powers collide, and, encircled by the world’s four great powers, it remains highly vulnerable to geopolitical competition and the damage it brings.

Korea's regional standing was once summed up in the image of a shrimp caught in a clash of whales. More recently, following the growth of its national power into that of a middle power, that standing has been elevated from "shrimp" to "dolphin." Korea's essential character as an "in-between state," however, remains unchanged, and it has yet to escape the risks that geopolitical competition has produced. Today Korea is a global middle power, a major trading state, and an advanced manufacturing power. Yet it is at the same time a "divided state" beset by zero-sum security competition with North Korea, a "resource-poor state" that can only make a living by trading actively, and a "state vulnerable in economic security" with a high degree of external dependence, leaving it more susceptible than any other country to geopolitical and geoeconomic shocks.

Faced with the current era of international disorder and great-power politics, Korea is in urgent need of a new geostrategy. As part of an answer to this problem, the previous Yoon Suk Yeol government put forward the concept of a "Global Pivotal State," and the current Lee Jae-myung government has advanced a "Globally Responsible Power" and "Pragmatic Diplomacy centered on National Interest," yet none of these conceptions adequately articulates the geostrategic dilemmas confronting Korean diplomacy, let alone answers them. This paper therefore proposes the "in-between state" as the concept that best captures Korea's essential geopolitical attributes, and on that basis sets out and evaluates the geostrategic options available to it.

2. The “In-Between State”: Concept and Cases

A. Conceptual Definition and Related Concepts

Concepts similar to the "in-between state" include the "pivot state" and the "middle state"; their respective emphases and distinctions are discussed below. This paper primarily uses the concept of the "in-between state" because it best captures the inherent geopolitical attributes of a state caught between competing great powers.

An "in-between state" is a country located in a region where the spheres of influence of multiple great powers overlap, and over which those powers compete to bring it under their exclusive sphere. Among "in-between states," small and medium-sized states with a certain degree of autonomy and strong internal cohesion become "bridge states," while weaker ones that are internally divided and vulnerable to external pressure become "shattered states."

The concept of the "pivot state," frequently used in academic circles, refers to a small or medium-sized state located where the spheres of influence of multiple great powers overlap; one that possesses military, economic, and ideological strategic assets coveted by the surrounding great powers; and one whose shifts in foreign relations bear significantly on regional and global security, so that the interests of the great powers come into conflict over it. The "pivot state" concept, however, differs from that of the "in-between state," which describes an objective geopolitical condition, in that it foregrounds the state's diplomatic autonomy to "pivot."

For example, in The Grand Chessboard (1997), former U.S. National Security Advisor Zbigniew Brzezinski referred to states whose strategic value is high owing to their distinctive geopolitical position amid great-power rivalry as "strategic pivots." He identified five countries as representative "strategic pivots" on the Eurasian continent: Ukraine, South Korea, Azerbaijan, Turkey, and Iran; in many of these regions intense geopolitical competition is unfolding today.

The concept of the "middle state" takes "geopolitical factors" into account in order to analyze the foreign policies and diplomatic patterns of states that cannot be explained by existing size-based concepts of the middle power or the small and medium-sized state, and to enhance the explanatory power of such analysis.

B. Historical Cases of the "In-Between State"

First, the fate of a weak state caught between competing great powers was vividly recorded in the "Melian Dialogue" of The History of the Peloponnesian War, written some 2,500 years ago by the Greek historian Thucydides. When Melos, then a colony and ally of Sparta, was invaded by the hostile great power Athens, it proposed neutrality and pleaded to be allowed to survive; but Thucydides, speaking through the Athenians, dismissed the Melian appeal with the famous diplomatic maxim that "the strong do what they can, and the weak suffer what they must." Melos had expected support from its patron great power, Sparta, but Sparta turned a blind eye to Melos in order to avoid direct conflict with its rival Athens; the fate of Melos thus epitomizes the tragedy, transcending time and place, of small and medium-sized "in-between states" situated among great powers.

Second, there is Finland, caught in the power struggle between Russia and Germany in the twentieth century. After Finland gained independence from Russia in 1917, Germany sought to bring it into its sphere of influence in order to use it as a forward base for an attack on Russia, while Russia sought to do the same in order to protect St. Petersburg (Leningrad), which was vulnerable to a German assault; each thus competed to draw Finland into its own sphere of influence. During the interwar period from 1919 to 1939, Finland pursued a policy of neutrality in order to secure full independence and diplomatic autonomy from both Germany and Russia, but it was ultimately drawn into the Winter War of 1939 to 1940, launched by the Soviet Union, suffering the loss of some territory and massive casualties.

In 1948, Finland signed the Finno-Soviet Treaty of Friendship, Cooperation, and Mutual Assistance and pursued a foreign and security policy known as "Finlandization," which consisted of the following principles. First, Finland would not allow its territory to be used as a transit route for foreign troops invading Russia; second, it would not join any military alliance hostile to the Soviet Union; and third, it would maintain non-alignment and neutrality in diplomacy, as well as political autonomy. Since then, Finland has actively participated in the United Nations and other international organizations, maintaining a high international standing by emphasizing peace diplomacy, development cooperation, international law, human rights, and multilateralism. In particular, as seen in the 1975 Helsinki Conference on Security and Cooperation in Europe (CSCE) and the Helsinki Final Act, Finland successfully played the role of mediator and bridge state in the interstices of great-power rivalry.

Third, there is Ukraine, caught in the power struggle between Russia and the Western bloc. Geopolitically, Ukraine is a strategic linchpin situated between NATO/the EU and Russia, and Russia has consequently designated "Ukraine's accession to NATO" as a red line that must be prevented at all costs. Building on the revival of its national power, President Putin annexed the Crimean Peninsula in 2014 and, in 2022, invaded Ukraine to rebuild its "strategic depth," a move reminiscent of Russia's traditional "near abroad" strategy of establishing strategic buffer zones.

Since gaining independence, Ukraine has experienced severe confusion in its geopolitical identity, oscillating between pro-Western and pro-Russian policies with each change of government. As a result, Ukraine's "pivot diplomacy" strategy failed: it lost the Crimean Peninsula to Russia and, following the Donbas conflict, suffered a full-scale Russian invasion. The Yushchenko administration (2005–2010), born out of the Orange Revolution, pursued a policy of distancing itself from Russia, causing relations with Moscow to deteriorate significantly; the subsequent Yanukovych administration (2010–2014) pursued a pro-Russian policy, but this only served to further exacerbate the strife and division between pro-Russian and pro-Western factions.

Fourth, the tragedy of the "in-between state" is being replayed today in the Gulf region of the Middle East. This applies to the small and medium-sized Gulf states caught between the United States and Iran in a time of war, such as the UAE, Qatar, Bahrain, Oman, and Kuwait, which are drawn into U.S. attacks on Iran and also face retaliatory strikes from Iran. Solely by virtue of their geopolitical status as "in-between states," these Gulf states, though not enemies of Iran, have become major military targets; they have suffered economic damage as severe as that of the warring parties; and, despite being struck one-sidedly, they find themselves reluctant to launch a military counterattack.

To counter the political and military threat posed by Iran, an immediate neighbor, a regional power, and a state with a vastly different political system, the Gulf states chose to seek the security backing of the United States, the world's leading superpower and a major maritime power. In return, they provided the United States with approximately 10 naval and air bases and hosted about 30,000 U.S. troops. In peacetime, U.S. bases and forces in the Gulf contributed not only to the regime security and national security of the Gulf states but also to peace and stability across the Middle East.

As the limits of its power-projection capabilities made it difficult to strike directly at U.S. forces deployed far away, Iran concentrated its attacks on U.S. bases in the neighboring Gulf states. As a result, the "entrapment in war" that the Gulf states had striven to avoid came to pass. At this point the Gulf states confront a serious geostrategic dilemma. Were they to refuse the United States the use of their military bases, it would amount to "alliance abandonment." Should they launch direct retaliatory strikes against Iran, they would likely provoke Iranian counter-retaliation and escalation, and there is no guarantee, moreover, that U.S. security protection would prove effective or permanent.

3. An All-Weather Portfolio: Korea’s Diplomatic Strategy

As the best geostrategic option for protecting and expanding South Korea's national interests (security, peace, prosperity, and unification), this paper proposes a strategy titled "ROK-U.S. Alliance Plus Hedging Diplomacy," which centers on the ROK-U.S. alliance as the fundamental pillar while simultaneously fostering a strategic cooperative partnership with China and, in addition, promoting regional cooperation and solidarity with like-minded states.

A. Reaffirming and Expanding the Shared Interests of the ROK-U.S. Alliance in the Twenty-First Century

The ROK-U.S. alliance was the foremost political, economic, and security asset and a key factor in South Korea's success, as it guaranteed the security and economy of the newly founded nation and enabled it to emerge as a middle power today. Moreover, there is a broad public consensus that even in today's era of new geopolitics the alliance remains South Korea's foremost economic, diplomatic, and security asset, and it should therefore be utilized to the fullest.

Some conservative experts in both South Korea and the United States cite Japan as a model for strategy toward China and call on South Korea to join a U.S.-Japan-led anti-China front. Yet South Korea differs markedly from Japan in national scale, in the short distance and direct geographical proximity between South Korea and China, in the special relationship between North Korea and China, in the high degree of the Korean economy's external dependence, and in the scale of its trade with China, so that South Korea's geopolitical interests inevitably differ from those of Japan. Moreover, as both a regional superpower and South Korea's largest trading partner, China wields powerful diplomatic and economic leverage over South Korea, so that South Korea must avoid conflict with China and manage the Korea-China relationship with great care.

According to the lessons of power politics and strategic theory across all ages and places, the ROK-U.S. alliance is a natural alliance; South Korea should therefore build on its achievements and traditions while redefining and reaffirming the alliance's values and interests as follows in order to prepare for the new geopolitical environment.

First, South Korea should reaffirm that the foremost mission of the ROK-U.S. alliance is to deter North Korea from provoking war and to deter its use of nuclear weapons, and to that end should continue close political and military cooperation with the United States.

Second, South Korea should oppose expanding the ROK-U.S. alliance into a regional alliance directed against China. It would join an anti-China front only in the event that China adopts a militarily hostile posture toward South Korea; even then, it should expand that mission cautiously and incrementally, commensurate with China's assertiveness. In fact, the mere presence of U.S. Forces Korea on Korean soil serves to check the expansion of Chinese military power beyond the Korean Peninsula into the maritime domain. A strong South Korean military, moreover, amply performs the function of a breakwater against the expansion of Chinese military power beyond the peninsula into the Western Pacific, and the United States, too, should be persuaded to recognize this distinctive Korean role in regional peace and stability.

Third, South Korea should pursue ROK-U.S.-Japan trilateral security cooperation but must, for the time being, take care to keep its scope confined to North Korea. This is because, if such cooperation were directed against China, China's retaliatory measures would concentrate on South Korea, the weak link in the trilateral relationship and the one with high economic dependence on China.

B. Regional Cooperation Among South Korea, China, and Japan for Peace and Shared Prosperity in Northeast Asia, and Solidarity Among Like-Minded States in East Asia

As the strategic competition between the United States and China intensifies, South Korea will become increasingly exposed to risks in the areas of diplomacy and security, economy and trade, and supply chains. To mitigate the shock of a U.S.-China clash and expand its strategic options, South Korea should therefore actively pursue, in parallel, trilateral cooperation among South Korea, China, and Japan; South Korea-Japan middle-power solidarity; and regional solidarity in East Asia.

South Korea should not suspend cooperation with Japan despite the history problem and strategic mistrust between the two countries. Japan is an economic powerhouse, a regional power, and a key state with influence over U.S. policy toward Asia, so that any escalation of tensions between South Korea and Japan would adversely affect South Korea's peninsula policy, its diplomacy toward the United States, and its economic-security strategy. For this reason the Lee Jae-myung government, too, maintains a proactive stance on South Korea-Japan cooperation in accordance with its principle of "pragmatic diplomacy."

Next, China, as South Korea's closest neighbor and the region's sole superpower, is a country of vital importance to South Korea's security and economy. South Korea therefore actively pursues a China policy of deepening and advancing the "ROK-China Strategic Cooperative Partnership," with the aim of stably managing bilateral relations and expanding economic cooperation.

Since the end of the Cold War, the South Korean government has actively sought regional cooperation in Northeast Asia in order to stably manage the competitive relationships between the United States and China and between China and Japan, to respond to North Korea's nuclear threat, and to prepare for a possible future weakening of the ROK-U.S. alliance. The Lee Jae-myung government, too, is pursuing regional cooperation as a means of expanding diplomatic buffer space and strategic autonomy.

Since most small and medium-sized states of East Asia have long possessed the attributes of "in-between states" exposed to the risks of great-power rivalry and geopolitical conflict, South Korea should pursue a "multilateral strategic dialogue among like-minded states" with these countries. Here the experience of expanding political and security dialogue with ASEAN through the New Southern Policy in the mid-2010s would prove helpful.

South Pacific states such as Australia and New Zealand are likewise experiencing the dilemma of entrapment and abandonment amid U.S.-China competition, and so, together with ASEAN, they could build like-minded solidarity with South Korea and pursue strategic cooperation in preparation for developments in the U.S.-China relationship. Over the medium to long term, this paper proposes exploring the construction of an "East Asia-South Pacific Zone of Peace and Prosperity," involving South Korea and Japan, ASEAN, and the South Pacific states, that would not only respond to U.S.-China competition but also foster cooperation on free trade, supply chains, maritime security, climate change, health security, and cybersecurity.

C. Global Solidarity Among Like-Minded States

In this era of great-power politics and multipolarization, most small and medium-sized states across the Eurasian continent are being pressed by neighboring great powers into choices they do not want; this paper therefore proposes forming an "international solidarity of like-minded states" for a joint response. The first partners for such cooperation would be the states of Southeast Asia, Central Asia, and Eastern and Central Europe, located along the geopolitical fault lines of the Eurasian periphery. Having long endured the coercions of war, occupation, and partition between continental and maritime powers, these states share a strong geostrategic affinity with South Korea, which should make comprehensive political and economic cooperation feasible.

While the peripheral states of Eurasia have historically been an arena of conflict and great-power rivalry, they could convert their geopolitical vulnerability into a strategic asset if regional peace and cooperation were institutionalized. That is, by transforming the existing "shatter zone" into a "bridge zone" connecting continent and ocean and the eastern and western regions, they could serve as a buffer that eases geopolitical competition in the space where the U.S. Indo-Pacific Strategy and China's Belt and Road Initiative collide.

South Korea should also pursue a "solidarity of like-minded and value-sharing states" with U.S. allies and Western middle powers that favor multilateralism and a rules-based international order. In particular, it should actively pursue strategic cooperation with those U.S. allies that, following President Trump's recent remarks downplaying the importance of alliances, share concerns about "alliance abandonment." Together with Germany, France, Australia, Canada, and Japan, South Korea should broaden cooperation to cushion the shock of U.S. unilateralism and to preserve rules-based global governance.

Finally, this paper proposes that, in this era of new geopolitics, South Korea redefine the identity and mission of MIKTA and develop it into a core platform for global solidarity among like-minded states. It bears recalling that MIKTA is a vital diplomatic asset, being a rare consultative body of middle powers whose establishment South Korea spearheaded. MIKTA, which comprises major middle powers and regional powers such as South Korea, Australia, Mexico, Turkey, and Indonesia, previously sought cooperation to advance mutual interests within the existing framework of global governance; now, however, it must take on the new mission of easing great-power rivalry and safeguarding rules-based global governance.