The weight of a treaty alliance
Published: 22 Apr. 2025, 00:04
Yoo Jee-hye
The author is the head of the diplomatic and security news department at the JoongAng Ilbo.
When Donald Trump was re-elected as president of the United States, seasoned foreign policy officials in Seoul braced for renewed turbulence. For those working in defense cost-sharing negotiations, the anxiety is summed up in a single word: “SMA,” short for the Special Measures Agreement, the deal that determines how much Korea contributes to the upkeep of U.S. Forces Korea (USFK).
![U.S. soldiers salute the American flag at Camp Casey in Dongducheon, Gyeonggi, on July, 2023. [YONHAP]](https://koreajoongangdaily.joins.com/data/photo/2025/04/22/41dc71d9-5820-4e39-bf78-76789e95f928.jpg)
In his first term, Trump focused obsessively on the bottom line. He demanded a fivefold increase in Korea’s contribution and pushed for Seoul to also shoulder costs related to strategic asset deployment and rotational forces. When those demands met resistance, Washington floated the idea that if Korea would not pay more, it should contribute personnel instead — suggesting participation in initiatives such as the U.S.-led naval coalition in the Strait of Hormuz.
Now back in office, President Trump is taking a different approach. He wants to bundle the defense cost-sharing issue with trade, reportedly warning that unless Korea sharply increases its SMA contribution and reduces its trade surplus with the United States, the U.S. might consider withdrawing its troops. Trump reportedly called this a “one-stop shopping” approach.
His stance comes amid shifts in U.S. defense priorities. A recently leaked Pentagon strategic planning guide emphasizes burden-sharing, indicating that regional allies should assume greater responsibility for threats like North Korea, while Washington focuses more squarely on China. That has triggered speculation over a potential reduction or reorientation of USFK.
Meanwhile, Japan has proposed integrating the Korean Peninsula, East China Sea and South China Sea into a single “one theater” of operations — a move reportedly welcomed by the United States. This would signal a strategic pivot, shifting the mission of USFK from North Korea deterrence to containing China.
But before panicking over dramatic change, it is worth revisiting the legal foundation of the Korea-U.S. alliance.
Three key treaties uphold the alliance: the Korea-U.S. Mutual Defense Treaty in the security domain, the Korea-U.S. FTA in the economic field and the Korea-U.S. Nuclear Cooperation Agreement in energy cooperation. Among them, the Mutual Defense Treaty is the bedrock, forming the legal core of what is often called a “treaty alliance.”
![U.S. Forces Korea (USFK) helicopters are seen at Camp Humphreys in Pyeongtaek, Gyeonggi, on April 9. [YONHAP]](https://koreajoongangdaily.joins.com/data/photo/2025/04/22/d28edb90-c5cd-49bc-975a-c1e8598df6ce.jpg)
The preamble to that treaty affirms the two nations’ “common determination” to deter any potential aggressor from entertaining the illusion that either Korea or the United States would stand alone in the Pacific. Article II commits both sides to maintain and develop their capacity to resist armed attack, and Article IV stipulates that U.S. forces may be stationed in and around Korea “as agreed.”
The treaty makes clear that any unilateral U.S. retreat or shift of military assets out of Korea would require mutual consent and run counter to the foundational purpose of the alliance.
That foundation was reaffirmed in 1992 when Korea and the United States signed a comprehensive agreement on wartime support. It commits the United States to the security and territorial integrity of Korea, affirms that the presence of U.S. troops is a visible sign of America’s defense commitment and confirms that the U.S. plans to reinforce forces on the Korean Peninsula in case of crisis, hostilities or war.
The SMA itself is explicitly rooted in the Mutual Defense Treaty. Its full title — “Agreement between the Republic of Korea and the United States of America on Special Measures Concerning Article IV of the Mutual Defense Treaty and Article V of the Status of Forces Agreement (SOFA)” — underscores this link.
Under Article V of SOFA, the United States was originally responsible for covering all non-facility-related expenses for USFK. But as Korea’s economy grew in the 1990s, Seoul began partially sharing costs, at Washington’s request. This exception to the rule is what the SMA legally codifies — a special measure for a specific case.
Even so, Korea’s obligations are clearly defined. Seoul contributes to three areas: labor costs for Korean personnel supporting USFK, military construction and logistical support. There is no legal basis for paying for other categories — including the kinds of operational or global strategic expenses that Trump is now suggesting.
Despite the difficulty of each SMA round — including the latest 12th agreement concluded last year — Korea has consistently defended this position in negotiations. At no point has it agreed to expand the scope beyond what is legally grounded in the treaty framework.
This context makes clear that Trump’s “defense cost–tariff bundle” is not only unreasonable but incompatible with treaty obligations. Any defense of Korea’s stance must begin with the legal architecture of the alliance.
![Japan's minister of economic revitalisation Ryosei Akazawa arrives at Prime Minister Shigeru Ishiba's official residence in Tokyo on Oct. 1, 2024. [REUTERS/YONHAP]](https://koreajoongangdaily.joins.com/data/photo/2025/04/22/bee9eb0f-2fff-420d-a2fa-a934969810f9.jpg)
While some flexibility within the SMA is possible — such as reforming how cost-sharing is calculated by moving from a lump-sum model to a needs-based approach — extending the conversation to tariffs is a dangerous overreach. This is not just negotiation, but treaty erosion.
Rather than rushing into a lopsided deal, Seoul would do well to closely monitor Japan’s experience. Having walked into Washington’s “one-stop shopping” trap first, Tokyo may offer a cautionary tale worth studying.
Translated from the JoongAng Ilbo using generative AI and edited by Korea JoongAng Daily staff.
The author is the head of the diplomatic and security news department at the JoongAng Ilbo.
When Donald Trump was re-elected as president of the United States, seasoned foreign policy officials in Seoul braced for renewed turbulence. For those working in defense cost-sharing negotiations, the anxiety is summed up in a single word: “SMA,” short for the Special Measures Agreement, the deal that determines how much Korea contributes to the upkeep of U.S. Forces Korea (USFK).
U.S. soldiers salute the American flag at Camp Casey in Dongducheon, Gyeonggi, on July, 2023. [YONHAP]
In his first term, Trump focused obsessively on the bottom line. He demanded a fivefold increase in Korea’s contribution and pushed for Seoul to also shoulder costs related to strategic asset deployment and rotational forces. When those demands met resistance, Washington floated the idea that if Korea would not pay more, it should contribute personnel instead — suggesting participation in initiatives such as the U.S.-led naval coalition in the Strait of Hormuz.
Now back in office, President Trump is taking a different approach. He wants to bundle the defense cost-sharing issue with trade, reportedly warning that unless Korea sharply increases its SMA contribution and reduces its trade surplus with the United States, the U.S. might consider withdrawing its troops. Trump reportedly called this a “one-stop shopping” approach.
His stance comes amid shifts in U.S. defense priorities. A recently leaked Pentagon strategic planning guide emphasizes burden-sharing, indicating that regional allies should assume greater responsibility for threats like North Korea, while Washington focuses more squarely on China. That has triggered speculation over a potential reduction or reorientation of USFK.
Meanwhile, Japan has proposed integrating the Korean Peninsula, East China Sea and South China Sea into a single “one theater” of operations — a move reportedly welcomed by the United States. This would signal a strategic pivot, shifting the mission of USFK from North Korea deterrence to containing China.
But before panicking over dramatic change, it is worth revisiting the legal foundation of the Korea-U.S. alliance.
Three key treaties uphold the alliance: the Korea-U.S. Mutual Defense Treaty in the security domain, the Korea-U.S. FTA in the economic field and the Korea-U.S. Nuclear Cooperation Agreement in energy cooperation. Among them, the Mutual Defense Treaty is the bedrock, forming the legal core of what is often called a “treaty alliance.”
U.S. Forces Korea (USFK) helicopters are seen at Camp Humphreys in Pyeongtaek, Gyeonggi, on April 9. [YONHAP]
The preamble to that treaty affirms the two nations’ “common determination” to deter any potential aggressor from entertaining the illusion that either Korea or the United States would stand alone in the Pacific. Article II commits both sides to maintain and develop their capacity to resist armed attack, and Article IV stipulates that U.S. forces may be stationed in and around Korea “as agreed.”
The treaty makes clear that any unilateral U.S. retreat or shift of military assets out of Korea would require mutual consent and run counter to the foundational purpose of the alliance.
That foundation was reaffirmed in 1992 when Korea and the United States signed a comprehensive agreement on wartime support. It commits the United States to the security and territorial integrity of Korea, affirms that the presence of U.S. troops is a visible sign of America’s defense commitment and confirms that the U.S. plans to reinforce forces on the Korean Peninsula in case of crisis, hostilities or war.
The SMA itself is explicitly rooted in the Mutual Defense Treaty. Its full title — “Agreement between the Republic of Korea and the United States of America on Special Measures Concerning Article IV of the Mutual Defense Treaty and Article V of the Status of Forces Agreement (SOFA)” — underscores this link.
Under Article V of SOFA, the United States was originally responsible for covering all non-facility-related expenses for USFK. But as Korea’s economy grew in the 1990s, Seoul began partially sharing costs, at Washington’s request. This exception to the rule is what the SMA legally codifies — a special measure for a specific case.
Even so, Korea’s obligations are clearly defined. Seoul contributes to three areas: labor costs for Korean personnel supporting USFK, military construction and logistical support. There is no legal basis for paying for other categories — including the kinds of operational or global strategic expenses that Trump is now suggesting.
Despite the difficulty of each SMA round — including the latest 12th agreement concluded last year — Korea has consistently defended this position in negotiations. At no point has it agreed to expand the scope beyond what is legally grounded in the treaty framework.
This context makes clear that Trump’s “defense cost–tariff bundle” is not only unreasonable but incompatible with treaty obligations. Any defense of Korea’s stance must begin with the legal architecture of the alliance.
Japan's minister of economic revitalisation Ryosei Akazawa arrives at Prime Minister Shigeru Ishiba's official residence in Tokyo on Oct. 1, 2024. [REUTERS/YONHAP]
While some flexibility within the SMA is possible — such as reforming how cost-sharing is calculated by moving from a lump-sum model to a needs-based approach — extending the conversation to tariffs is a dangerous overreach. This is not just negotiation, but treaty erosion.
Rather than rushing into a lopsided deal, Seoul would do well to closely monitor Japan’s experience. Having walked into Washington’s “one-stop shopping” trap first, Tokyo may offer a cautionary tale worth studying.
Translated from the JoongAng Ilbo using generative AI and edited by Korea JoongAng Daily staff.
with the Korea JoongAng Daily
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