March 17, 2021

South Korea Is an Island, Entire of Itself: The Missing Island in Allied First Island Chain Strategies

Insight from the Pitch 2020: A Competition of New Ideas

Korea’s strategic geography makes it the perennial battleground and compass of great-power rivalry in Asia. For centuries, whoever controlled Korea controlled Asia. Historical predecessors to modern-day China, Japan, and Russia violently and repeatedly fought for control of the Korean Peninsula, causing the “shrimp among whales” to suffer numerous wars instigated by dueling competitors vying for hegemony in the western Pacific. Located at the nexus of continental and maritime East Asia, Korea was the gateway for maritime invaders or the first line of defense for continental powers. A change in Korea’s alignment mirrored a reorientation in Asia’s true north and, in all these wars, navies, not armies, were the decisive factor for the victor. Today, South Korea is one of the United States’ closest allies and a sovereign democratic nation with high-end warfighting capabilities that functions as a de facto island. By reimagining South Korea as the missing island in allied First Island Chain strategies, Washington can solidify its approach to South Korea as a fundamental building block of allied maritime security strategies in the Indo-Pacific and foster closer U.S.-ROK-Japan-Australia defense cooperation.

For 75 years, South Korea has been isolated from the Asian continent and has functioned politically, economically, socially, and militarily as an island nation. It remains entirely dependent on air and sea trade and the demilitarized zone blocks the overland exchange of people, goods, information, and ideas. Korea possesses over 400 years of maritime innovation dating back to Admiral Yi Sun Shin’s armored “turtle ships” that defeated the Japanese navy in two 16th-century invasions, despite being outnumbered over 25 to 1. This naval legacy is visible today in the Republic of Korea’s (ROK) development of aircraft carriers, attack submarines, and naval warplanes.

By reimagining South Korea as the missing island in allied First Island Chain strategies, Washington can solidify its approach to South Korea as a fundamental building block of allied maritime security strategies in the Indo-Pacific.

However, Washington today is repeating the mistakes of former Secretary of State Dean Acheson when he excluded Korea from the Asia defense perimeter in 1950, thus failing to recognize Korea as a fundamental geographic building block of U.S. maritime security strategies in the Pacific. Decades later, Washington still bases its understanding of Korea’s geographic significance on the outdated historical restraints of the Korean War. Washington views South Korea largely as a land-based conventional deterrent against North Korea, rather than a key maritime security ally whose strategic and operational significance extends well beyond the Korean Peninsula. But by reimagining South Korea as the missing link in the First Island Chain, the United States can better empower its ally with maritime-focused infrastructure investments, logistics, defense exports, security cooperation, and joint combined military exercises. This will enhance conventional deterrence, expand allied anti-access/area-denial architecture closer to China, and expand the U.S.-ROK alliance beyond the littoral waters of the Korean Peninsula into the blue waters of the Indo-Pacific.

U.S.-China strategic competition looms large over the Asian security environment, but the United States is a relative newcomer to great-power competition in the region. During the Imjin Wars, Joseon Korea’s navy of turtle ships and Ming China’s army twice thwarted Toyotomi Hideyoshi’s invasions in 1592 and 1597, which sought to expand Japan’s empire to continental Asia by way of Korea. China’s intervention on Korea’s behalf and Japan’s ultimate failure to secure a foothold on the Asian continent later established Korea as a Chinese tributary state and ushered in almost 200 years of Japanese isolationism, enabling China’s ascendance as Asia’s dominant power.

Three centuries later, Japanese ships invaded Korea once again to challenge China for regional preeminence and, this time, they succeeded. After opening to the West, Imperial Japan experienced major industrialization in the late 1800s and the Imperial Japanese Navy fashioned itself after the British model and embraced the principles of Western maritime strategists. During the First Sino-Japanese War (1894–1895), Japan defeated Qing China, winning its first colony—Taiwan—and first continental sphere of influence—Korea—and replaced China as Asia’s hegemon.

With China defeated, Japan turned toward its next great-power competitor, Russia, whose growing influence in Korea and Manchuria threatened Japan’s expansionist ambitions. Rising tensions between the two erupted into the Russo-Japanese War (1904–1905), leading to Russia’s subsequent defeat and Japan’s annexation of Korea as a colony in 1910, elevating Japan’s status from regional to global great power. Japan’s rise, however, ended less than half a century later with its defeat in World War II (1939–1945), forcing Japan to relinquish its colonies, including Korea, along with its great-power status. Shortly afterwards, the Soviet Union and United States, Asia’s next dueling duo, divided newly emancipated Korea along the 38th parallel. The Soviet Union and China assumed patronage over their communist comrades in the north and the United States over their newly democratic kin in the south. Thus, competing political ideologies and associated alliances set the conditions that ignited the Korean War (1950–1953), which to all in Asia has remained anything but forgotten.

U.S.-China strategic competition looms large over the Asian security environment, but the United States is a relative newcomer to great-power competition in the region.

Today, Korea’s role in U.S.-China competition is even more critical than in centuries past. South Korea is a major middle power that ranks among the world’s largest economies, most active democratic cultures, most innovative technological industrial bases, and most capable high-end militaries. But Seoul and Washington alike continue to confine the alliance to the peninsula, failing to see South Korea as part of the First Island Chain—the geographic blueprint for allied Indo-Pacific strategies and operational planning—despite China’s inclusion. Like many U.S. allies and partners, Seoul’s reticence toward embracing a forward-leaning counter-China stance stems from fears of Chinese retaliation, such as economic coercion tactics—fears validated by actions such as Beijing’s economic retaliation against Seoul following its decision to host Terminal High Altitude Air Defense (THAAD) deployments in 2017.

Recently, however, Seoul appears to be growing into its modern maritime security identity and taking significant steps toward fostering closer strategic relationships with countries outside of its immediate vicinity in light of Beijing’s increasing acts of aggression and coercion in the region. Ironically, the 2017 THAAD incident pushed Seoul to diversify its economic options to decrease its dependence on China and deepen economic ties with Southeast Asian countries and India through its New Southern Policy. Through its Defense Reform 2.0 initiative, South Korea continues to increase its defense spending, reform and modernize its military, equip its armed forces with the latest technology, and revitalize its defense industrial base. The ROK Navy has expanded its participation and taken on leadership roles in multilateral maritime exercises, such as the Rim of the Pacific and Pacific Vanguard exercises, training alongside Australia, Japan, and the United States.

To lay the foundation for greater U.S.-ROK-Japan-Australia defense cooperation, Washington should foster closer ally-to-ally relations by concurrently supporting stronger ROK-Australia defense collaboration and closer ROK-Japan relations. These overlapping, dyadic ties among three of the United States’ closest and most capable allies in the Indo-Pacific will become springboards from which South Korea extends its strategic and operational reach and becomes another layer upon the latticework that comprises Asia’s minilateral and multilateral regional architecture.

By reimagining South Korea as the missing island in allied First Island Chain strategies, Washington can reconceptualize the maritime geography of Asia to compete more effectively against China while buttressing its existing alliances and shaping the regional security environment together with its allies. Washington can then propel the U.S.-ROK alliance to extend beyond the Korean Peninsula and secure South Korea’s role as a key maritime security ally in the Indo-Pacific.

The opinions expressed are those of the author alone and do not reflect those of the U.S. Department of Defense or any part of the U.S. government.

About the Author

Grace B. Kim is a John S. McCain Strategic Defense Fellow in the Office of the Undersecretary of Defense for Policy. Prior to the Defense Department, she was a Senior Analyst at the Center for Strategic and Budgetary Assessments, where she led its Korea analysis and research on U.S. and allied defense strategies, long-term military competition, and trends in future warfare in the Indo-Pacific. She previously spent four years in Turkey analyzing European, NATO, and Middle East security policy as a Fulbright fellow and researcher at the Istanbul-based Centre for Economics and Foreign Policy Studies. Grace has held fellowships with Pacific Forum, George Washington University’s Institute for Korean Studies, and Schmidt Futures, among others. She received her MA in strategic studies and international relations from Johns Hopkins University School of Advanced International Studies and a BA in politics from Princeton University.


Thank you to Dr. John Park, Pacific Forum colleagues, and Dr. Toshi Yoshihara for their guidance and generosity in providing intellectual resources and mentorship to develop my idea early on. Special thanks also go to Olivia Garard, Khyle Eastin, and Lauryn Williams for providing constructive feedback, valuable edits, and a reliable sounding board from the brainstorming to writing process. I am also grateful to Kristine Lee, Carisa Nietsche, William MacKenzie, and The Pitch team for helping me prepare my idea for publication. Finally, thank you to the Center for a New American Security for providing a platform for emerging national security voices to be heard.

About The Pitch

In 2020, the Center for a New American Security (CNAS) launched a premier event to elevate emerging and diverse voices in national security. Selected applicants made their pitch for innovative policy ideas to renew American competitiveness in front of a distinguished panel of judges and live virtual audience at the CNAS National Security Conference on June 24, 2020. Winners included Grace Kim (Best in Show and Military and Defense Heat Winner), Tina Huang (People's Choice Award), Luke Chen (National Security Institutions Heat Winner), Khyle Eastin (Alliances and Multilateralism Heat Winner), and Alan McQuinn (Economics and Technology Heat Winner).


The Pitch 2020: A Competition of New Ideas

In 2020, the Center for a New American Security (CNAS) launched a new premier event to elevate emerging and diverse voices in national security. Selected applicants made their...

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