South Korea and the Strait of Hormuz: The Limits of American Influence over Seoul

João Pedro Nascimento

The United States has been pressuring South Korea to contribute to efforts aimed at restoring freedom of navigation in the Strait, which is considered strategic for the international flow of oil, natural gas, and other commodities. The Donald Trump administration has made it clear that it expects greater participation from its allies, and South Korea occupies a particularly relevant position because it is one of Asia’s largest industrial economies and is highly dependent on energy imports from the Middle East.

For Seoul, however, possible military participation could be interpreted by Iran as direct support for the campaign led by the United States, exposing South Korea to potential diplomatic, economic, or even security retaliation. At the same time, a refusal could generate costs within the relationship with Washington itself, precisely when the two countries are negotiating strategic issues such as nuclear-powered submarines, nuclear technology, the transfer of operational control during wartime, and the future of the American military presence on the Peninsula.

The problem is that what Seoul considers a defensive contribution may not be interpreted in the same way by Tehran. For Iran, the presence of foreign forces assisting maritime security in the Gulf may be enough to characterize it as support for the American campaign. South Korea’s room for maneuver, therefore, is extremely narrow.

An alliance built during the Cold War

To understand why Washington has such significant capacity to exert pressure on Seoul, it is necessary to return to the origins of the bilateral relationship. The alliance between the United States and South Korea was built in the context of the Korean War and the consolidation of the bipolar order of the Cold War. The Mutual Defense Treaty established the foundations for military cooperation and paved the way for a permanent presence of American forces on the Peninsula.

South Korea had been devastated by the war and faced a North Korea supported by the Soviet Union and China. The United States, on the other hand, was a global power with incomparably greater economic and military capabilities. The fundamental logic of the alliance was the provision of military support by the United States, while South Korea remained under the American security umbrella. For Washington, the Korean Peninsula also represented a strategic position within its power architecture in Northeast Asia, as it allowed the United States to maintain an advanced position vis-à-vis North Korea, but also vis-à-vis China and the Soviet Union. South Korea, therefore, was simultaneously a state to be protected and a strategic platform for the projection of American power in Asia.

Today, the Peninsula is located at the center of one of the most militarized regions on the planet, close to China, Japan, Russia, and, of course, North Korea. South Korea also possesses one of the most capable armed forces among American allies. This means that, for Washington, South Korea is capable of making a significant contribution to the regional security architecture. This relationship has become even more important as American strategy has shifted from being focused exclusively on North Korea toward increasingly considering the rise of China.

For much of the Cold War and the period that followed, the main question was how the United States could defend South Korea from North Korean aggression. Today, another question is beginning to gain importance: how can the U.S.–South Korea alliance contribute to the American strategy in the Indo-Pacific?

South Korea is beginning to move from a predominantly beneficiary role of American protection toward a position as a potential contributor to the global strategy of the United States. And it is precisely this transformation that helps explain why an issue located in the Persian Gulf can acquire such importance for the relationship between Washington and Seoul.

Hormuz and the logic of American influence

The pressure on South Korea regarding Hormuz is part of a broader transformation in American foreign policy. Washington seeks to make its allies assume a greater share of the costs associated with maintaining the international order and American presence.

This logic is associated with the more transactional view of alliances held by the Trump administration, as the president has reinforced the idea that the United States should no longer be solely responsible for global “stability.” In other words, the implicit message is that if the United States assumes costs to protect its allies, those allies should also be willing to assume costs when the United States needs support.

South Korea depends on the alliance for an important part of its deterrence against North Korea, depends on American cooperation for certain military technologies, is negotiating the transfer of OPCON with Washington, and seeks support for its nuclear-powered submarine projects and for issues related to the nuclear fuel cycle.

Thus, a decision regarding Hormuz can acquire significance far beyond its immediate military meaning. Seoul knows that a contribution can facilitate the maintenance of a positive relationship with Washington. Likewise, it knows that a refusal could complicate future negotiations. The very perception that Washington possesses instruments capable of affecting South Korean strategic interests already generates bargaining power. This is one of the most important elements of contemporary American foreign policy.

The crisis can also be understood as a test of loyalty within the alliance. For the Trump administration, the issue is relatively convenient. If South Korea participates, the United States obtains additional military resources while simultaneously demonstrating that its allies are willing to share the costs of its strategic initiatives. If Seoul refuses, Washington can argue that South Korea is not contributing proportionally to the security it receives. Participation in Hormuz demonstrates alignment with the United States, while refusal can be interpreted as a pursuit of autonomy by South Korea.

However, it would be mistaken to interpret this relationship as a simple situation of South Korean submission. The asymmetry of power favors Washington, but South Korea possesses its own bargaining instruments. Its importance to American strategy is precisely one of these sources of power. Washington needs Seoul to maintain an effective security architecture in Northeast Asia, and South Korea is also important in relation to North Korea and China. Therefore, the relationship does not function as an absolute hierarchy.

Furthermore, there is domestic politics. The government of Lee Jae-myung needs to take parliament and public opinion into consideration, since the deployment of armed forces abroad requires approval from the National Assembly, and opposition to involvement in the conflict is not limited to the political opposition, as there is also resistance within the governing camp itself. This means that Lee has a legitimate justification for limiting his response to Washington.

South Korean foreign policy is not determined exclusively by American preferences. Rather, it is the result of the interaction between external pressures and domestic constraints, as is the case in many states.

South Korea’s strategy

Seoul appears to be seeking a contribution that is significant enough to preserve its relationship with Washington, but limited enough to prevent South Korea from becoming a direct participant in the war against Iran.

A maritime patrol aircraft can be presented as an instrument of navigation security. A mine-clearing team can be presented as a humanitarian and defensive capability. Unmanned systems can be deployed to identify maritime threats.

Politically, this allows Lee to attempt to satisfy three different audiences:

·         Washington can see a concrete contribution;

·         South Korean society can see a defensive mission rather than a war;

·         The international community will perceive a contribution to freedom of navigation in the Strait.

The difficulty is that a limited solution may not fully satisfy the Trump administration. If the American objective is simply to protect navigation, certain South Korean capabilities may be sufficient. But if Hormuz is being used as a mechanism to test allied commitment, Washington may interpret limited participation as insufficient.

The more Washington pressures Seoul, the greater the incentive for South Korea to offer something. However, the greater the American demands, the greater the domestic resistance and the risk that South Korea will conclude that it is being incorporated into conflicts that do not directly correspond to its interests.

Thus, American influence may reach a point of saturation. And beyond that point, additional pressure may produce a greater search for autonomy, because the South Korean government may perceive that the conflict in the Middle East is also consuming American military resources that could otherwise be used in the Indo-Pacific. If the United States is transferring capabilities to the Middle East, to what extent does its capacity to protect the Peninsula remain intact? In this way, the war in the Middle East may cause these same allies to question the American ability to remain fully committed to Asia.

If this perception deepens, the result could be contrary to American interests. A South Korea that considers its dependence on Washington excessively risky may accelerate investments in its own capabilities. The debate over nuclear weapons, for example, could gain strength if extended American deterrence is perceived as less reliable.

There could also be greater diplomatic diversification. Seoul does not need to abandon Washington in order to move closer to Beijing and can simply seek greater room for maneuver between the major powers. This is relevant because South Korea has an unavoidable economic and geographic relationship with China. Closer Chinese relations with Seoul, therefore, could offer a diplomatic alternative that may gain importance if the relationship with Washington becomes excessively coercive.

The fundamental dilemma of this analysis

“To what extent can South Korea support the United States without allowing Washington’s strategic priorities to determine its own foreign policy?”

The war against Iran is not a war directly related to the defense of the Korean Peninsula. Therefore, Seoul does not have the same strategic obligation that it would have in the face of a crisis involving North Korea. On the other hand, South Korean security depends deeply on the American alliance. A significant rupture or deterioration in the relationship could have consequences far greater than the Hormuz issue itself.

Lee therefore needs to preserve the alliance without turning alignment into absolute political dependence, since the Strait of Hormuz is merely another manifestation of American influence over South Korea. The alliance that was born to protect the South from the North is gradually transforming into a partnership with global reach, in which Washington expects Seoul to contribute to different fronts of American strategy.

This represents a natural evolution of South Korean power. An economically powerful and militarily advanced South Korea can contribute more, but it also means that Seoul is beginning to question which commitments genuinely correspond to its national interests.

The very structure of the alliance provides sufficient instruments to induce certain choices, especially when Washington possesses the ability to influence issues that Seoul considers strategic. If the United States goes beyond a certain point, pressure may cease to produce alignment and begin to produce a reaction, as mentioned earlier. A more militarily autonomous South Korea, more open to diplomatic diversification, and more willing to question the extent of its commitment to American operations would be a paradoxical consequence of Washington’s own pressure policy.

Therefore, the true geopolitical significance of Hormuz lies in this test of whether the U.S.–South Korea relationship will continue to be based predominantly on its historical logic or move toward a new configuration in which Washington expects Seoul to share the costs of its global strategy, while Seoul simultaneously seeks to transform its position from that of a dependent ally into that of a strategic partner with greater decision-making autonomy. At its core, it is a dispute over who defines the limits of South Korean foreign policy.

ReferencesA. SMITH, Sheila. Trump’s South Korea Social Post Poses Risks for the United States. Disponível em: <https://www.cfr.org/articles/the-risks-behind-trumps-south-korea-social-post>.

J. LONGO, Daniel. U.S.-South Korea Alliance: Background and Issues for Congress. Disponível em: <https://www.congress.gov/crs-product/R48877>.

JOO-YOUNG, Hwang. Is sending officials to UAE a sign Seoul is leaning towards Hormuz deployment? - The Korea Herald. Disponível em: <https://www.koreaherald.com/article/10867864>.

WHAN-WOO, Yi. Lee caught in Hormuz deployment dilemma. Disponível em: <https://www.koreatimes.co.kr/foreignaffairs/20260909/lee-caught-in-hormuz-deployment-dilemma>.

João Pedro Nascimento, Bacharel em Relações Internacionais, com pós-graduação em Políticas Públicas. Com experiência em internacionalização de negócios, expansão para mercados externos, negociações internacionais e gestão estratégica de parcerias. É consultor em política externa e economia internacional, além de sócio de um escritório de assessoria financeira, conectando empresas e investidores a oportunidades globais por meio de análise de cenários, avaliação de riscos e estruturação estratégica. Fundador do RI Talks, espaço independente de análise e debate sobre o cenário nacional e internacional.