By Daily Touch Insights Editorial Team
Editorial Team
View Journalist Profile
WORLD & INTERNATIONAL RELATIONS — The relationship between the United States and South Korea has entered a more complicated phase under President Donald Trump, with the long-standing military alliance increasingly shaped by questions over defence spending, military exercises, trade and Washington's renewed interest in diplomacy with North Korea.
The alliance itself remains in place, but Trump's approach has made the relationship more transactional and less predictable than under previous U.S. administrations.
The latest tension came after Trump ordered the Pentagon to substantially reduce joint military exercises with South Korea, arguing that the drills are costly and send an unnecessarily hostile signal to North Korea. The decision has raised new questions in Seoul about the future of the alliance and the reliability of the U.S. security commitment.
A Long-Standing Military Alliance
The United States and South Korea have maintained a formal military alliance for more than seven decades.
American forces remain stationed in South Korea as part of the effort to deter North Korea and respond to a potential military crisis on the Korean Peninsula.
For Seoul, the U.S. military presence has traditionally been one of the central pillars of national security because North Korea possesses nuclear weapons, ballistic missiles and a large conventional military.
For Washington, South Korea is also an important strategic partner in East Asia and part of the broader American security network in the Indo-Pacific.
Trump's First Term Changed the Conversation
Trump's first presidency introduced a very different tone into the alliance.
Rather than treating the military relationship as an unquestioned commitment, Trump repeatedly focused on how much the United States was spending to maintain its forces and conduct exercises in South Korea.
He also criticised major joint military exercises as expensive and unnecessary, particularly while diplomatic efforts with North Korea were underway.
Some exercises were subsequently reduced or suspended during Trump's diplomatic engagement with North Korean leader Kim Jong Un.
That experience established a pattern that has now returned during Trump's second presidency.
Trump's Direct Diplomacy With Kim Jong Un
One of the most dramatic changes under Trump has been his personal diplomacy with North Korean leader Kim Jong Un.
Trump became the first sitting U.S. president to meet a North Korean leader when he held a summit with Kim in Singapore in 2018.
The two leaders later met again in Hanoi and at the Korean Demilitarized Zone.
Those meetings created enormous international attention, but they did not produce a lasting agreement that ended North Korea's nuclear weapons programme.
North Korea continued developing its military capabilities after the diplomacy broke down.
Trump is now attempting to reopen communication with Kim, and he has again emphasised his personal relationship with the North Korean leader. 1
The Military Exercises Have Become a Flashpoint Again
The latest dispute centres on joint U.S.-South Korean military exercises.
Trump has ordered the Pentagon to substantially reduce American participation in the exercises, arguing that they are expensive and that they send a hostile signal to North Korea.
The decision came as the annual Ulchi Freedom Shield exercises were beginning.
The drills are designed to improve the ability of U.S. and South Korean forces to operate together in the event of a conflict and to maintain military readiness against potential threats from North Korea. 2
The precise extent of the reduction has been a major subject of discussion because military readiness depends partly on the ability of allied forces to train together.
Why Seoul Is Concerned
South Korea's security environment is fundamentally different from that of many other U.S. allies.
North Korea is located directly across the border and possesses nuclear weapons and increasingly sophisticated missile capabilities.
For South Korean officials, joint military exercises are therefore not simply political demonstrations.
They are part of the preparation required to coordinate American and South Korean forces during a crisis.
Any reduction in training can therefore raise questions about how quickly the two militaries could operate together if circumstances deteriorated.
South Korea Wants Greater Military Independence
Trump's pressure has also strengthened calls inside South Korea for greater military self-reliance.
President Lee Jae Myung has repeatedly argued that South Korea should develop stronger independent defence capabilities.
Lee has also pushed for South Korea to regain wartime operational control of its forces from the United States during his presidency.
The debate has become more urgent following Trump's decision to reduce joint exercises.
In effect, Washington's demand that Seoul carry more of the security burden is increasingly being met by South Korean efforts to strengthen its own military capabilities. 3
Trump's Approach Is More Transactional
The fundamental difference in Trump's approach is that he frequently evaluates alliances through questions of cost, contribution and reciprocal benefit.
South Korea is therefore being asked to contribute more to its own defence while also supporting broader American strategic interests.
This approach does not necessarily mean that Trump wants to abandon the alliance.
Instead, it suggests that he wants the relationship to operate on terms in which Washington believes the costs and responsibilities are more evenly distributed.
Defence Spending Has Become More Important
South Korea has increased its defence spending and has sought to demonstrate that it is willing to take greater responsibility for national security.
That is important because one of Trump's longstanding criticisms of allies has been that the United States carries too much of the financial burden.
The more Seoul invests in its own military capabilities, the stronger its argument becomes that it is already carrying a significant share of the alliance's responsibilities.
Trade Has Added Another Layer of Tension
The relationship is not limited to military affairs.
Trade has become another major source of friction between Washington and Seoul under Trump.
Trump's tariff policies have placed pressure on South Korean exporters and created uncertainty for major industries including automobiles, steel, technology and manufacturing.
South Korea has responded by negotiating with Washington while also increasing investment commitments in the United States.
The result is a relationship in which the two countries remain deeply economically connected while simultaneously arguing over the terms of that relationship. 4
South Korean Investment in America Is Growing
South Korean companies have become major investors in the American economy.
Industries including batteries, semiconductors, automobiles and advanced manufacturing have attracted significant Korean investment in the United States.
These investments create jobs and strengthen supply-chain connections between the two countries.
For Washington, they also provide evidence that Seoul can contribute economically to American strategic priorities.
The North Korea Question Remains Central
Despite disagreements over trade and military policy, North Korea remains the issue most directly connected to the security alliance.
South Korea wants effective deterrence against Pyongyang while also seeking opportunities to reduce tensions.
Trump's willingness to communicate directly with Kim Jong Un creates both an opportunity and a risk for Seoul.
Diplomacy could reduce tensions if it produces meaningful negotiations.
But South Korea could become concerned if Washington makes major decisions about North Korea without sufficiently involving Seoul.
Seoul Is Also Trying to Improve Relations With North Korea
President Lee's government has expressed interest in reducing tensions with Pyongyang.
South Korea has taken steps intended to lower confrontation along the border and has expressed support for renewed dialogue.
Seoul has also welcomed the possibility that Trump's relationship with Kim could eventually lead to negotiations between Washington and Pyongyang.
However, North Korea has so far remained reluctant to engage seriously with South Korea and has continued strengthening its military relationship with Russia. 5
The Alliance Is Not Collapsing
It would be an exaggeration to describe the latest disputes as the end of the U.S.-South Korea alliance.
The two countries continue to maintain extensive military, economic and diplomatic relationships.
American forces remain stationed in South Korea, and both governments continue to recognise the importance of cooperation in dealing with regional security threats.
The more accurate description is that the alliance is being renegotiated politically.
Trump is pushing Seoul toward greater financial and military responsibility, while South Korea is trying to preserve the American security commitment without becoming completely dependent on Washington.
Trust Has Become More Important
One of the most difficult issues is not simply military capability but trust.
South Korea needs confidence that the United States would respond if North Korea launched an attack.
The United States, meanwhile, wants confidence that South Korea will contribute to shared strategic objectives rather than relying on American power while pursuing its own priorities.
That balance becomes harder when Washington changes military policies suddenly or links alliance decisions to unrelated disputes.
China Adds Another Strategic Dimension
The U.S.-South Korea relationship also exists within a much larger competition involving China.
Washington wants its Asian allies to contribute to regional security and maintain a stronger strategic position in the Indo-Pacific.
Seoul, however, has significant economic relationships with China and must carefully manage its relations with Beijing.
South Korea therefore has to balance three major interests: its alliance with the United States, its economic relationship with China and the immediate threat from North Korea.
The Alliance Could Become More Self-Reliant
There is one possible long-term consequence of Trump's approach that should not be ignored.
Pressure from Washington could encourage South Korea to become significantly more militarily independent.
Greater defence spending, stronger domestic weapons production and efforts to regain wartime operational control could reduce Seoul's dependence on American forces over time.
That could ultimately produce a more capable South Korean military.
But the transition also carries risks if the reduction of U.S. involvement happens faster than South Korea can build the capabilities required to replace it.
The Biggest Risk Is Miscalculation
The most dangerous outcome would not necessarily be a formal collapse of the alliance.
It would be uncertainty.
If North Korea becomes unsure about the strength of American deterrence while South Korea is still adjusting to a greater independent role, Pyongyang could miscalculate the willingness of the allies to respond to aggression.
At the same time, Washington and Seoul must avoid allowing disagreements over spending, trade or diplomacy to weaken basic military coordination.
What Comes Next
The future of the relationship will depend heavily on how Trump balances his desire for diplomacy with North Korea against the military requirements of the U.S.-South Korean alliance.
Seoul will also have to decide how quickly it wants to increase its independent military capabilities and how much it is willing to contribute to broader American strategic priorities.
Meanwhile, any renewed Trump-Kim dialogue could dramatically change the political environment on the Korean Peninsula.
Our Perspective
The biggest mistake would be to interpret every Trump decision as proof that the U.S.-South Korea alliance is ending.
That is too simplistic.
What is actually happening is more consequential: the old model of the alliance is being challenged.
Trump wants South Korea to spend more, assume more responsibility and accept a more transactional relationship. Seoul, meanwhile, is beginning to prepare for a future in which it cannot assume that Washington will always provide the same level of military support.
The strongest long-term alliance may ultimately be one in which South Korea is capable of defending itself while the United States remains a powerful and reliable partner. The danger is getting from the current model to that future without creating a security gap.
Conclusion
The U.S.-South Korea relationship under Donald Trump has evolved from a traditional security alliance into a more complicated partnership shaped by defence spending, military readiness, trade and Trump's personal diplomacy with North Korean leader Kim Jong Un.
Trump's decision to reduce joint military exercises has revived one of the most sensitive issues from his first presidency and created new concerns in Seoul about military readiness and the reliability of the alliance.
At the same time, South Korea is responding by pushing for stronger independent defence capabilities and greater control over its own military operations. 7
The relationship therefore appears to be entering a new phase rather than simply falling apart.
The central question is whether Washington and Seoul can build a more balanced alliance without weakening the deterrence that has kept the Korean Peninsula from returning to open conflict.
