U.S. President Donald Trump’s decision to substantially reduce the U.S.-ROK combined military exercise should concern South Koreans, but not simply because one exercise will be smaller. Exercises can be adjusted for diplomatic or operational reasons. The more important issue is what the decision tells us about changing American expectations toward its allies and whether South Korea understands that change.
Trump’s disappointment with South Korea is understandable. Washington increasingly expects allies to contribute to challenges the United States considers important to international security. His frustration over Seoul’s reluctance to participate in U.S. efforts concerning Iran reflects his broader belief that alliances cannot be one-way arrangements in which America responds to threats facing its allies while those allies remain distant from challenges confronting the United States.
But South Korea faces serious security challenges of its own. It confronts a nuclear armed North Korea with increasingly sophisticated missiles, growing cooperation with Russia, and a large conventional military immediately across the border. Seoul must also manage its complicated relationship with China while remaining prepared for a conflict that could begin with little warning. These realities do not excuse South Korea from supporting its principal ally, but Washington needs to understand them. The disagreement over Iran therefore should not be reduced to whether Seoul simply said “yes” or “no.”
South Korea has a direct national interest in the stability of the Middle East. Korea has every reason to want the Strait of Hormuz open and secure as soon as possible. Freedom of navigation through this critical maritime artery affects energy supplies, shipping costs, and the Korean economy. Korea therefore shares an important strategic interest with the United States even if the two governments differ over how that interest should be defended.
Seoul must translate that shared interest into meaningful action without creating unnecessary additional security risks. Intelligence sharing, maritime surveillance, logistical assistance, protection of commercial shipping, diplomatic support, and carefully defined military cooperation should all be considered. Alliance solidarity does not always require identical contributions, but it does require meaningful ones.
The manner in which the exercise reduction was announced nevertheless sends an unsettling message to America’s allies in Asia. Alliance commitments may increasingly be viewed through a transactional lens and potentially adjusted according to the President’s relationship with an adversary. For South Korea and Japan, the deeper concern is whether decisions affecting deterrence are coordinated with allies and accompanied by reciprocal measures from the adversary. North Korea should not receive something for nothing.
Combined exercises are not political theater. They allow American and Korean forces to practice command relationships, communications, reinforcement, logistics, and complex operations that cannot be improvised after a crisis begins. Readiness is perishable. Repeatedly reducing training without effective alternatives will eventually have consequences. American and Korean military professionals will certainly find creative ways to carry out President Trump’s direction while maintaining readiness. But there is a larger lesson for Seoul: South Korea cannot afford to repeatedly disappoint the United States and assume the alliance will simply absorb the consequences. At the same time, Korea must do a much better job of explaining its situation to Washington. Alliance management is not merely about accepting American requests. American leaders must understand Korea’s threat environment, constraints, capabilities, and what Seoul is prepared to contribute. That requires sustained communication and trust.
Washington also has responsibilities. Alliances depend on predictability, consultation, and confidence that decisions affecting collective defense will be made collectively. When major changes are announced publicly and linked to a personal relationship, allies inevitably begin asking how much they can rely on American commitments during a future crisis. This does not mean the U.S. alliance system in Asia is collapsing. Its treaties, military relationships, shared interests, and decades of cooperation remain substantial. But uncertainty has cumulative consequences. It encourages allies to strengthen independent defense capabilities and eventually consider strategic options they previously regarded as unnecessary.
Finally, the strategic environment is becoming less forgiving. Russia and North Korea are cooperating more closely. China is increasingly assertive. Middle Eastern instability has global consequences. The United States expects more from its allies, while those allies expect greater predictability from Washington. For South Korea, the conclusion should be uncomfortable but clear: being in the middle is no longer an option.
Seoul does not have to agree with Washington on every issue, nor should it automatically participate in every American operation. But when vital American interests are at stake, Korea must demonstrate that it understands the burden of alliance. Likewise, when Korea’s survival and security are at stake, it must expect the same from the United States. That is what an alliance ultimately means: not unquestioning obedience, but mutual confidence that when circumstances become difficult, neither side will discover that the other has chosen to stand aside.
Retired Lt. Gen. Chun In-bum is the former commander of the Republic of Korea Army Special Warfare Command.