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ISSN 2816-1971

  • Seonjou Kang

The ROK-U.S. Alliance at 70: A Political Economic Explanation of Its Endurance

In examining the alliance between the Republic of Korea and the United States, it is possible to use a political economic lens to explain its lasting endurance, despite the seemingly one-sided dynamic of the relationship.

Photo credits: Atlantic Council

The ROK-U.S. alliance celebrates the 70th anniversary in 2023. The two countries signed the Mutual Defense Treaty in October, 1953 after the Korean War was ended. The ROK-U.S. alliance is an asymmetric alliance, in which power distribution between the ROK and the U.S. has been skewed toward the latter. The central goal of this paper is to examine what factors have contributed to the endurance of the ROK-U.S. alliance spanning seven decades. Findings from this study would shed light on not only alliance research in general but also the state of security in the Indo-Pacific region.


1. Framing the Endurance of the ROK-U.S. Alliance

Explanations of alliance formation and duration, in other words, under what conditions states form alliances and terminate them, largely converge toward three factors:

(1) External threats: States form alliances for the purpose of increasing their security against common enemies.

(2) Capability: States consider the military assistance that will be added to their own in deterring common threats.

(3) Domestic politics: Like all policies, alliance is also subject to political considerations. Even if a state faces external threats, it is likely to evaluate security as a national goal in relation to other domestic goals and choose alliance, among available alternatives, based on both costs/benefits and domestic support.

These three factors can have influence on one another. If any of the three conditions that led to the formation of an alliance changes, the alliance is likely to face change eventually affecting the longevity of the alliance. The changes that the three conditions of alliance formation undergo respectively are:

(1) External threats: Member states of an alliance may develop divergent threat perceptions and the necessity of the alliance due to changes in international relations.

(2) Capability: Changes in the capabilities of allied states can affect rationales for the alliance. An alliance member whose capabilities have increased may seek to terminate the alliance and instead increase military spending for self-defense. Particularly in asymmetric alliances, where the weak parties are vulnerable to interference in domestic politics and foreign policy from the stronger parties due to the power gap between them, increases in the weaker parties’ capabilities may lead to terminating the alliances in order to gain autonomy.

(3) Domestic politics: Changes in domestic politics, which are by and large associated with democratization, can affect alliance cohesion, if newly elected leaders in democratizing countries see alliance differently from their predecessors and feel less committed to the alliance.


2. The Endurance of the ROK-US Alliance

The theoretical framework for alliance which triangulates external threats, capabilities, and domestic politics can be applied to explaining the endurance of the ROK-U.S. alliance.

In terms of alliance formation, first, the external threats that led the ROK and the U.S. to form the alliance were North Korea. The two countries sought to defend South Korea against North Korea. Nevertheless, it should be noted that the two countries treated the threats from North Korea somewhat differently. While the ROK viewed North Korean threats at the level of the Korean peninsula only, the U.S. regarded them at the systemic level. The U.S. believed that North Korea was part of a larger struggle against communist expansion.

Secondly, the ROK–U.S. alliance was asymmetric in nature since there was a large gap in power distribution between the two countries. South Korea could not contribute much to the alliance, while the U.S. bore a massive portion of their mutual defense treaty. The U.S. deployed troops and even tactical nuclear weapons in South Korea. From 1954 to 1971, the US provided $2.5 billion in military aid and deployed on average 63,000 combat troops. The U.S. poured over $3.2 billion in economic aid as well in order to rebuild the war-ravaged South Korea and shore up its defense capabilities. When South Korea adopted an export-oriented development strategy from early 1960s, the U.S. opened its markets to South Korean products.

Thirdly, for South Korea, alliance with the U.S. was imperative and not questioned at all over three decades especially under its authoritarian regime. Similarly, the U.S. supported the alliance with the ROK despite the authoritarian nature of South Korean regime since the U.S. prioritized fighting communism during the Cold War.

From early 1990s, however, the ROK–U.S. alliance started to undergo changes in all three factors that formed their alliance. First, with the end of the Cold War, the threat of communist expansion disappeared, and North Korean aggression remained the only security concern. From there South Korea and the U.S. developed divergent threat perceptions. South Korea started to view North Korea as less threatening and more compatriotic. However, the U.S. came to face a different dynamics of deterrence, as North Korea pursued nuclear weapons along with a ballistic missile force to deliver them.

Secondly, thanks to economic development, South Korea has built a modern, capable military. Military balance between the South and the North tilted in favor of the former. South Korea has also taken on a greater share of its own defense and increased its share in the cost of U.S. forces stationed in South Korea. The U.S. even reduced its forces in Korea in order to support its war efforts in Vietnam and Iraq. From then on, the U.S. forces in South Korea stand about 28,500.

Lastly, South Korea’s economic development and democratization engendered a broad array of national interests including security and the alliance with the U.S. Anti-American sentiments, demand for improving inter-Korean relations, and diplomatic and economic engagement with China caused fluctuations in the ROK-U.S. alliance. Decline in support for the alliance with the U.S. was visible under progressive governments, while the alliance with the U.S. was appreciated better when conservative governments were in power. On the U.S. part, with the rise of China, the U.S. sought to broaden the operational scope of the ROK-U.S. alliance beyond the Korean peninsula but South Korea remained reluctant to commit itself to it.  

Recently the ROK-U.S. alliance is going through a significant realignment. The three factors that caused serious fluctuations in the alliance are now working to strengthen the alliance. The ROK and the U.S. are in consensus to maintain their alliance on a more equal footing and reconfigure its scope and role given the severe changes in international relations of the 2020s. Thus, it is safe to say that the endurance of the ROK-U.S. alliance spanning seven decades results from both the ROK and the U.S. succeeding in adapting to changes in the external threats, capability, and domestic politics and incorporating them back into their alliance.

DISCLAIMER: All views expressed are those of the writer and do not necessarily represent that of IIPA and this platform.


Seonjou Kang is Professor at Korea National Diplomatic Academy-Institute of Foreign Affairs and National Security (KNDA-IFANS). Her research centers on rules-based international order/global governance, geo-economics of Asian regionalism, and economic security. Her widely cited research include “The US-led Indo-Pacific Economic Framework for Prosperity,” “G7 Summit 2021 and the Post-Pandemic International Order,” “US-China Competition for Monetary Finance Hegemony,” “The US Indo-Pacific Strategy as Geo- economics,” “South Korea and France’s Indo-Pacific Strategies: Potential Partnership and Challenges” (IFRI).



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