When US President Donald Trump announced a reduction in American participation in joint military exercises with South Korea, many observers saw it as a concession to North Korea or a strain on the alliance. But history suggests that Trump is not breaking new ground. The US-South Korea defense relationship, often portrayed as a pillar of stability in the Indo-Pacific, has actually seen repeated periods of flux and attempts by successive American presidents to trim the US footprint.
The most famous example came in 1977, when President Jimmy Carter proposed withdrawing all US ground forces from South Korea. The plan ignited a firestorm of political and military opposition, both in Washington and Seoul, and Carter eventually backed down. Yet even after that reversal, the numbers kept falling. In the late 1970s, roughly 41,000 US troops were stationed in Korea; today, the figure hovers in the mid-20,000s.
That decline occurred despite the US presence in Korea rarely becoming a major political issue in American domestic politics. Until Trump's recent decision to curtail exercises, the alliance seemed to operate on autopilot. But the underlying trend has been one of gradual reduction, not expansion.
America's 'defensive perimeter'
The roots of this ambivalence go back to the end of World War II. The US had no intention of maintaining a large permanent force on the Korean Peninsula. When Japan surrendered in 1945, the peninsula's future was uncertain. It was divided into a US zone of occupation in the south and a Soviet zone in the north, with separate states emerging in 1948. The US withdrew its remaining troops in 1949, just before the Korean War broke out.
Even as Washington sought to build a democratic ally in Seoul, the Truman administration's strategic priorities lay elsewhere—primarily in Japan and the Philippines. The US maintained a military advisory mission and supplied arms and equipment, but it did not envision a large garrison. This low ranking in American priorities was made explicit in January 1950, when Secretary of State Dean Acheson, in a speech before the National Press Club, omitted Korea from a list of Asian countries and areas that the US considered part of its defensive perimeter. Many analysts believe that omission emboldened the Soviet Union and North Korea to launch their invasion later that year.
Trump's current approach, while less dramatic than Carter's proposal, fits into this historical pattern of periodic reassessment. His administration has framed the exercise reduction as a cost-saving measure and a way to reduce tensions with Pyongyang. But critics worry that it undermines the credibility of the US commitment to South Korea, especially as South Korea rethinks its reliance on the US alliance.
The move also comes at a time when North Korea continues to develop its military capabilities, including new naval assets that signal a shift toward blue-water power. The reduction in exercises could be seen as a signal of waning US resolve, even if the underlying numbers of troops remain relatively stable.
For Seoul, the challenge is to manage its security dependence on Washington while preparing for a future where the US presence may be less certain. South Korea's path to strategic autonomy has become a topic of serious debate, not just among academics but within the government and military.
Trump's decision is not an isolated act of presidential whim. It is the latest chapter in a long story of American ambivalence about its military footprint on the Korean Peninsula. The alliance has survived previous reductions, but each one raises the question of how much the US is willing to commit to a region that, for decades, has been central to its Indo-Pacific strategy.
As the region watches, the key issue is not whether Trump's move is unprecedented—it is not—but whether the alliance can adapt to a new normal of reduced exercises and shifting strategic priorities. The history of US-Korea relations suggests that such adaptations are possible, but they come with risks and require careful management from both sides.
