US President Donald Trump shared on his social media an opinion article from the "Washington Post", which claims that South Korea should send its "Cheongung-II" air defense system to Ukraine.
In addition, the administration of the US head of state continues to put pressure on Seoul to send troops to the Strait of Hormuz. Neither the US-Iran war nor the Russia-Ukraine war are new to the geopolitical landscape, but the simultaneous pressure from the US on Seoul to both help in the war with Iran and support Ukraine is striking, write Jun-Seok Lee and Donghyeon Kim in their analysis for War on the rocks.
While such divergent demands are indeed unprecedented, this is partly due to the lack of principles defining a clear position for South Korea. The state should establish a principle requiring multilateral legitimacy before deploying its troops abroad.
The country should also create a legal framework for arms sales to partners such as Ukraine, modeled on the World War II-era "Lend-Lease" law. In the absence of such principles, Seoul will continue to act erratically whenever an ally or partner makes a request, ultimately creating an impression of unpredictability and unreliability.
The issue of possibly sending troops to the Strait of Hormuz is complicated by Seoul’s own interests in Iran. Seoul and Tehran have built cultural ties dating back to the 1969 Treaty of Friendship and the mutual naming of streets in 1977, as well as economic ties that have historically employed more than 200,000 South Koreans in Iran’s infrastructure sector.
In their analysis, Jun-Seok Lee and Donghyun Kim recall that as recently as 2017, Iran provided 13.2% of South Korea’s oil imports, making it the third-largest supplier. These relations still carry significant financial weight. South Korea held about $6 billion worth of frozen Iranian oil revenues between 2018 and 2023, which were only released as part of a separate U.S.-Iran prisoner swap.
Beijing and Moscow have interests in these conflicts that far exceed Seoul’s. China buys up to 90 percent of Iran’s oil exports, making it far more vulnerable to disruptions in the Strait of Hormuz than South Korea.
China, South Korea’s largest trading partner, has also resorted to economic retaliation in response to Seoul’s deployment of the Terminal High Altitude Area Defense (THAAD) missile defense system. It’s an experience Seoul cannot afford to ignore. Russia also issued a similar warning directly to Seoul.
When Seoul considered joining a NATO-sponsored initiative to help buy American weapons for Ukraine, the Russian Foreign Ministry threatened "countermeasures, including those of an "asymmetric" nature." Both powers have a greater stake in these conflicts and have a greater capacity to respond than South Korea.
A problem without a solid plan of action
In the past, Seoul has sent troops to help its ally, the United States, as well as to support UN missions. For example, at the request of the United States, Seoul has sent about 320,000 troops to Vietnam, the largest foreign contingent after the United States itself.
South Korea also has the Zaytun division in Iraq from 2004 to 2008 as the third largest contingent. Seoul also maintains the "Ah" unit in the United Arab Emirates, "Dongmyeong" in the UN force in Lebanon, and "Hanbit" in South Sudan. This experience demonstrates a combination of providing assistance to allies, performing non-military tasks, and complying with the requirement for consent from the National Assembly.
However, Seoul needs a clearly formulated principle to regulate the sending of troops abroad in the future.
A telling example is that Seoul is leading a premature public discussion on the deployment of troops just weeks after annual joint military exercises with the United States were abruptly canceled and their scale reduced. Are joint military operations appropriate when the very exercises designed to prepare for combat readiness have just been cut?
While the internal debate in Seoul about the possible deployment of troops is reflected in the media, and the Ministry of Defense confirms that it has sent a team to study the situation in the strait area, the South Korean public is rightly asking itself the same question.
The South Korean presidential administration subsequently ordered an investigation to determine which institution had leaked information about internal deliberations, confirming that its own processes lacked the discipline that a well-established guiding principle would provide.
Adding further complication for policymakers in both the United States and South Korea is the fact that any deployment of troops abroad requires the consent of the National Assembly.
In April 2003, the National Assembly approved the deployment of non-combat engineering and medical units to Iraq. The more significant vote took place in February 2004, when it approved a separate and much larger deployment of troops, the "Zaytun" division, with a strength of about 3,000.
Seoul placed "Zaytun" under its own independent command, with its primary mission being peacekeeping. The name of the unit - "Zaytun" (Arabic for "olive") was chosen as a symbol of peace. The deployment of the contingent was based on UN Security Council resolutions 1511 and 1546 - a legal justification that is lacking in the current case related to Iran.
The crisis in relations with Iran during Trump's first term deepened after the attacks near Fujairah, the strike on "Saudi Aramco" facilities and the assassination of Qassem Soleimani. In response, Seoul decided to expand the scope of operations of the "Chonghae" contingent deployed in the region (Cheonghae), directing it to the Gulf of Oman and the Persian Gulf, but without joining the US-proposed "International Maritime Security Initiative".
This was a compromise decision aimed at both helping the US protect shipping lanes and energy imports and maintaining long-term relations with Iran. However, the expansion of the operational area of the "Cheonghae" contingent was carried out in a way that circumvented the requirement for consent from the National Assembly, which drew sharp criticism from lawmakers.
The actions were based on a clause in the contingent's deployment regulations that allowed for the expansion of the operational area to protect South Korean citizens in times of crisis. While the 2020 approach was an attempt to maintain some uncertainty in the complex geopolitical environment, such a scenario is inapplicable in the current situation of a heated conflict in the Strait of Hormuz.
Initial media reports, although the Ministry of Defense has not yet officially confirmed the information, indicate the possible use of assets such as P-8A "Poseidon" patrol aircraft, a Navy explosive ordnance disposal team, and a logistics support ship, with the envisaged missions ranging from surveillance to mine clearance operations.
However, the government and the ruling party acknowledge that such a mission requires the approval of the National Assembly, regardless of its non-military nature. The situation is further complicated by the ruling party's hesitation over the clarity and necessity of the mission, which raises questions about whether the government will be able to muster enough votes to obtain the necessary consent.
According to a survey conducted on September 7 among 1,020 South Koreans by the "Reform Institute" - 62.4% of respondents considered the US request to deploy forces in the Hormuz region unjustified. The same survey showed that 61.3% of respondents believed that the government had approached the issue incorrectly in presenting it to the public.
Independent surveys conducted the same week pointed in the same direction. A joint survey by four independent polling agencies found that 45% opposed deploying forces in the Strait of Hormuz, while 36% supported it. Meanwhile, another independent survey showed that public opinion was split within the margin of error - 47.1% against and 43% "for".
The "Reform Institute" survey also found that when forced to prioritize, 41.4% did not support either the deployment of forces in the Strait of Hormuz or the provision of weapons aid to Ukraine - a share larger than the individual options combined. The real conclusion is not that South Koreans unconditionally support participation in a coalition.
However, among those who admit the possibility of participation at all, the preference is categorically directed towards participation only within the framework of a coalition; this option was chosen by 37.6% of all respondents, as well as by 61.9% of those who considered the American request unjustified in a situation where the alternative was the absence of any action.
Furthermore, the "Reform Institute" survey shows that 84% of respondents believe that before any decision is made, there should be a discussion in the National Assembly and that it should be informed in advance.
When should South Korea send troops?
Foreign policy and national security are often seen as isolated from domestic politics, but the significance of the tariff issue shows that this separation is no longer entirely valid. Therefore, the results of the aforementioned survey have significant implications for the principles proposed in this text.
The principle should apply to cases in which Seoul would provide military support in an area of active conflict, such as the Strait of Hormuz. It is a decision complicated by the importance of the waterway to South Korea, which imports nearly two-thirds of its oil and one-fifth of its liquefied natural gas.
The United States and South Korea have a formal mutual defense treaty, but it does not cover conflicts initiated by either ally or conflicts beyond the administrative control of the parties. In such cases, the treaty applies only in the narrowly defined scenario in which one of the two countries is attacked.
Standard of multilateral legitimacy
Any deployment of South Korean troops in the Strait of Hormuz should be supported by multilateral legitimacy - be it through a recognized coalition or on the basis of comparable norms of international law, rather than being carried out as a stand-alone ad hoc operation.
In the past two years, Pyongyang has deepened its military cooperation with Moscow. The country has sent forces to fight in Russia’s war in Ukraine, but in exchange for technology transfers that improve its missile and intelligence capabilities.
At the same time, the scale of South Korea’s own combat readiness exercises has been scaled back. Faced with an adversary with greater capabilities and already committed to international alliances, South Korea’s armed forces have good reason to keep their available resources on the Korean Peninsula rather than dispersing them in the Persian Gulf region.
This is not an argument against any contribution, but rather a question of multilateral legitimacy, as opposed to the independent deployment of forces. All of this can provide capabilities and political legitimacy that Seoul is unable to generate on its own.
This legitimacy can take one of two forms. The first is a recognized coalition through a formally announced multinational effort with a publicly stated mission and named participants.
The second is based on a comparable legal basis in international law, which may include a UN Security Council resolution, an existing UN peacekeeping mandate, or an invocation of customary law to protect freedom of navigation.
What matters is the existence of one of these bases, not the operational command structure that Seoul subsequently chooses. For example, the "Zaytoun" division operated under Seoul's independent command, despite relying on a Security Council resolution, and the "Dongmyeong" contingent operated in full integration with the peacekeeping mandate of the UN Interim Force in Lebanon.
Both cases meet the requirements of the second basis, regardless of the command structure. The most telling example is the International Maritime Security Construct, established by the US in 2019 without UN authorization.
It demonstrates that the second ground can only be met by invoking customary freedom of navigation law, and that compliance with this standard does not oblige Seoul to participate in the initiative. When it was announced, Seoul expanded the operational area of its own "Chonghae" contingent rather than formally joining the new structure. A case that would not meet these criteria is a force deployment, such as the one currently under discussion, that does not enjoy any comparable multilateral support from either side.
This standard benefits both the United States and South Korea—both in the Strait of Hormuz situation and in future conflicts—by providing Washington with support that no single country could offer, while minimizing the risk that each side takes to support its allies.
If Washington opts for a quicker bilateral agreement and abandons coalition formation, Seoul should stand its ground rather than give up the principle under pressure. The resulting tension is a real cost to the alliance, but it is lower than the risk that a unilateral force deployment would create.
Furthermore, sending South Korean forces is logistically unfeasible. The destroyer, currently on the "Chonghae" rotational mission in the Gulf of Aden, is equipped to combat piracy, not to counter the threats of drones and mines in the Strait of Hormuz. The transit of Korean waters takes about a month, and the separation of ships from the fleet weakens defense capabilities at home at the very moment when the Korean Peninsula needs them.
Framework for arming partners in war
The second principle should clarify to whom and when Seoul exports its most advanced defense products. The immediate export of the "Cheongung-II" (KM-SAM Block II) system to Ukraine is limited for two reasons. The first reason is South Korea's long-standing policy of not exporting weapons to countries involved in active conflict. The second reason is the shortage of supplies related to existing contracts and commitments.
South Korean defense exporters require a permit from the Defense Acquisition Program Administration (DAPA - ed. note). Its issuance can be restricted under the regulations of the Defense Acquisition Program Act for reasons including a state of war.
In addition, the Foreign Trade Act separately limits permits to goods intended for "peaceful purposes". However, both restrictions fall under the scope of regulations or ministerial orders, not the laws themselves. This means that the government can tighten or loosen them only by a decision of the cabinet or the relevant minister, without the need for a vote in the National Assembly.
In the past, South Korea has supplied 155mm artillery ammunition to the United States, not to Ukraine, so as not to violate the policy in question. There is also a significant institutional difference in the procedures for selling arms abroad between Seoul and Washington.
Unlike the US Foreign Military Sales (FMS) program, which operates under congressional oversight, arms exports from South Korea are authorized administratively by the Defense Acquisition Program Administration.
Under the US Arms Export Control Act, foreign military sales above a certain monetary threshold must be formally notified to Congress, with fixed deadlines within which the transfer can be blocked by a joint resolution before it is carried out.
There is no such control mechanism in South Korea. A hypothetical sale of the "Cheongung-II" for Ukraine, however, would be approved entirely within the Defense Acquisition Program Administration and the Department of National Defense, while the National Assembly has no formal role, is not required to be notified, and lacks a statutory opportunity to object.
One way to overcome this gap is to introduce a legally regulated notification and objection mechanism. The Defense Acquisition Program Administration would retain its authority to approve or deny exports, but transfers above a certain threshold or those destined for areas of active conflict would require formal notification of the National Assembly of the decision made. Moreover, there should be a fixed period within which it could block an approved sale or request a review of a denied one.
In addition, the Lend-Lease Act of 1941 offers a model that could be adopted. Because this law authorized the provision of aid to any country “whose defense the President deems vital to the defense of the United States,” South Korea needs its own legal criteria. This would be aid tied to the partner’s importance to the rules-based international order or to the stability of the supply chains on which South Korea depends, rather than treating each transfer as an individual policy decision.
Such a defense framework, allowing the United States to arm Britain and other countries without becoming a party to the conflict itself, could lend greater flexibility to South Korea’s current policy on support for Ukraine.
It is true that this defense framework ultimately did not hold up in the case of the United States. Also, the Lend-Lease Act to protect democracy in Ukraine, adopted by the US Congress in 2022, has never been used. However, Seoul can start building a legal framework that will ensure predictability.
It is worth noting that the Lend-Lease Act required the US President to regularly report to Congress what assistance was provided and to which recipients. This should be a working model for the National Assembly notification mechanism needed to fill the institutional gap mentioned above.
South Korea's defense industry has seen significant growth over the past decade and is expected to continue to grow. However, it is unique in that its exports are inextricably linked to the country’s foreign policy and national security.
While many in Seoul welcome this growth and the associated economic benefits, the government must now define a clear principle for arms exports that protects and promotes South Korea’s vital national interests without turning the country into a participant in active conflicts.
From ad hoc decisions to strategy
The US administration’s continued demands to deploy troops in the Strait of Hormuz and export weapons to Ukraine have strained bilateral relations, further complicated by a trade and tariff agreement that many in the South Korean public view as inherently unfair.
However, one positive point is the growing recognition that South Korea needs clear principles: a standard requiring multilateral legitimacy for the deployment of troops in support of allies and partners, and a legal framework regulating arms sales to countries in peacetime and wartime.
The Strait of Hormuz and Ukraine are the most pressing issues facing Seoul's politicians today, but they will not be the last. Only a clear strategy will make South Korea a reliable ally and partner.