When empires fall: Post-American Asia and South Korea

As empires weaken or collapse, they either start wars to preserve themselves—or provoke wars through the chaos of their absence. The greater the empire’s role in shaping global or regional order, the more damaging its decline is likely to be—both for itself and for others.

For South Korea, a nation situated on the fault line of Northeast Asia’s rivalries and long dependent on American power for security, the implications of U.S. retreat are no longer theoretical. They are immediate, uncomfortable, and unavoidable.

South Korea has long built its national security on the assumption of a reliable and militarily dominant United States. Since the Korean War armistice in 1953, the U.S. has stationed troops on the peninsula, provided extended nuclear deterrence, and shaped the strategic boundaries of inter-Korean confrontation.

The result was a fragile but enduring peace, insulated by American primacy in Asia. That primacy is now in question—not just due to China’s rise or DPRK’s ICBMs and nukes, but more fundamentally because of the United States’ own internal decline: political division, eroding global commitment, and signs of strategic retrenchment.

The U.S. retreat from empire, if and when it accelerates, will not look like one grand withdrawal—it will be piecemeal, transactional, and cloaked in confusion. But for Korea, even a partial reduction in U.S. engagement carries outsized risks.

The American alliance has served not only as a deterrent against China and North Korea, but also as an ideological anchor that held the country together.

In the final years of the Chosun dynasty, Korea’s internal factions aligned with competing foreign powers to gain advantage. Reformists looked to Japan for support in modernizing the state, while conservative royalists initially leaned on Qing China to preserve traditional order. After China’s defeat in 1895, pro-Russian factions gained influence, especially around Queen Min, who sought Russian backing to counter Japan.

Others, disillusioned with regional powers, looked to more distant states like the United States or the United Kingdom as ideal partners. These rival alignments deepened internal instability and paved the way for Korea’s annexation by Japan in 1910.

Some Koreans view the division of the peninsula not just as a product of Cold War rivalry, but as the continuation of great power interference that began in the late Chosun era. From this perspective, the competing influences of Russia and China in the North, and the United States in the South, echo earlier patterns where Korean sovereignty was undermined by external powers manipulating internal factions. The 1945 division at the 38th parallel and the subsequent Korean War are seen as modern extensions of this historical pattern—foreign-led outcomes imposed on a nation caught between stronger rivals.

Would a retreating U.S. lead to internal divisions within South Korea? In many ways, those divisions are already emerging.

Political polarization has intensified, with segments of the left viewing U.S. withdrawal as a path to unification and realignment with China, while parts of the right see it as an existential threat demanding closer ties with Japan and even nuclear armament. As trust in longstanding security arrangements erodes, fringe ideologies gain ground, fueling public anxiety and ideological extremism. The prospect of U.S. disengagement is not merely a future scenario—it is already reshaping the political landscape.

Historically, the most dangerous period is not the moment of collapse, but the years of denial and overreach just before it. If the U.S. chooses to demonstrate its fading resolve with provocative shows of force—whether in Taiwan, the South China Sea, or the Korean Peninsula—Seoul may find itself trapped in a war that serves neither its interests nor its survival. There is also the problem of impulsiveness: a weakened empire often lashes out unpredictably, not with careful diplomacy but with sudden escalation.

In this light, Korea must ask: What happens if the U.S. starts a war it cannot finish? Or worse, what if it leaves a war unfinished?

There is precedent. The Ottoman Empire entered World War I seeking prestige and territorial redemption, only to collapse entirely. The Soviet Union’s quagmire in Afghanistan exposed deep systemic weakness and hastened its disintegration. Even Britain, after WWII, fought messy imperial exit wars in Kenya, Malaya, and Palestine—conflicts that left deep scars not just on those regions, but on Britain’s post-imperial psyche.

In each case, the empire’s death throes were marked not by dignity or control, but by chaos. The cost was paid largely by those living on each empire’s periphery. In 2025, South Korea lies on such a periphery.

For Korea’s current policymakers, the instinct is to hedge—deepen ties with China while maintaining the U.S. alliance. But that balancing act is growing more fragile by the day. Washington increasingly demands loyalty, not nuance. The Indo-Pacific framework, the NATO-IP4 arrangement, and trilateral cooperation with Japan all require political alignment with U.S. strategic goals. Korea’s current government, despite a change in leadership, is still bound by the momentum of these agreements.

If U.S. decline continues, Korea may become a “strategic orphan”.

The consequences of that strategic orphaning are not limited to security. Economically, the U.S. provides markets, investment, and technological cooperation. Politically, it offers an identity anchor—positioning Korea within a liberal democratic order. Psychologically, the U.S. presence provides a kind of reassurance: that Seoul is not alone in facing Pyongyang, Beijing, or Moscow.

The collapse of that reassurance, even gradually, would force Korea into a rushed rethinking of its defense posture, its nuclear policy, and even its constitutional assumptions about national sovereignty.

The first signs are already visible. Discussions once confined to fringe academic circles—about independent nuclear capability, about a more self-reliant military doctrine, about non-alignment—have entered the political mainstream.

These are not sudden shifts, but slow ideological adjustments, prompted by the creeping sense that the American order is no longer permanent. If U.S. decline continues, they will become unavoidable. But perhaps most dangerous is the illusion of continuity.

That Korea can continue to operate as it always has, that Washington’s commitments will remain firm, that strategic ambiguity will keep it safe. These assumptions are a luxury of the old order. The new reality is one of exposed frontlines and shrinking buffers. The longer Seoul clings to outdated security models, the more vulnerable it becomes to the geopolitical shock that American withdrawal would represent.

What should Korea do? There is no simple answer—but there is a simple truth: South Korea must prepare now for post-American Asia. That does not mean burning bridges, but it does mean thinking about and debating alternatives. It means investing in real deterrence, crafting a sovereign diplomatic identity, and recognizing that the world order that shaped the last seventy years is not the one that will shape the next seventy.

History tells us that when empires fall, they rarely go quietly—and they often drag their allies and adversaries alike into the fire. South Korea cannot afford to be caught unprepared. The time to prepare is not when the crisis comes. The time is now.