By shifting deterrence to its allies, Washington is unintentionally accelerating an arms race on the Korean Peninsula and expanding Pyongyang’s strategic leverage.

The latest US National Security Strategy (NSS) reflects a shift in how Washington directs its strategic attention. China remains at the center of the document, but the omission of any reference to North Korean denuclearization is particularly notable, especially since North Korea was treated as a central security concern in previous US doctrine, such as the 2017 NSS.

The silence on this issue is not merely rhetorical, but seems to reflect a deeper reordering of US priorities and a growing willingness to shift the burdens of deterrence and crisis management onto regional allies. In the case of the Korean Peninsula, that burden increasingly falls on South Korea. The result is not a managed transition toward regional stability, but a security environment that is growing more volatile, less predictable, and increasingly prone to escalation.

US Retrenchment Presents Opportunities for Pyongyang

Washington’s strategic shift is especially evident in its approach to the Korean Peninsula. North Korea no longer appears as a central concern within US Indo-Pacific strategy, and references to denuclearization are only confined to bilateral US–ROK fact sheet and US–ROK–Japan trilateral statements. These choices point to a growing expectation that Seoul, rather than Washington, will assume greater responsibility for managing the North Korean challenge.

From Pyongyang’s perspective, the NSS creates additional space to maneuver and reinforces the view that pressure directed at South Korea may produce strategic gains in terms of deterrence leverage and domestic legitimacy. Over the past several years, North Korea has reinforced this view through official speeches, doctrinal changes, and legislative measures that frame inter-Korean relations as fundamentally hostile. Furthermore, North Korea appears to be preparing to formalize a more rigid posture toward South Korea at its upcoming  Ninth Party Congress, potentially codifying a “two hostile states” doctrine and revising long-standing territorial provisions.

These developments are not directly caused by US retrenchment. However, Washington’s strategic shift reinforces Pyongyang’s inclination to institutionalize a more confrontational posture toward Seoul.

Altering the Status Quo by Degrees

Against this backdrop, North Korea’s military provocations appear to be part of a broader strategic agenda designed to serve dual purposes. One objective may be to take advantage of a gradual shift in US posture by incrementally challenging South Korea’s long-standing control over contested areas, particularly the Northern Limit Line (NLL) and the Korea Air Defense Identification Zone (KADIZ). Such domains are well-suited for calibrated provocations. Being strategically sensitive yet legally contested, they present a policy dilemma for Seoul: they are difficult to defend decisively without triggering disproportionate escalation.

Given North Korea’s enduring inferiority in conventional capabilities, this approach relies less on force parity than on nuclear-backed coercion. In this setting, escalation dominance plays a greater role than battlefield superiority in constraining South Korean responses and gradually altering the military status quo.

Another objective seems to be generating political strain within South Korea itself. By triggering debates over how Seoul should respond to North Korean provocations, as well as over the credibility of US extended deterrence and the future of the US–ROK alliance, Pyongyang can exploit domestic divisions and alliance asymmetries. Gray-zone pressure functions not only as a means of military signaling, but also as a form of political warfare.

The Limits of Political Constraint

Such a strategy rests on an assumption that is becoming harder to sustain: that South Korea’s response can be politically constrained without altering the underlying military balance on the Peninsula.

The current South Korean administration has announced a significant increase in military spending amid growing US pressure for greater burden-sharing. The government has stated that the annual defense budget will rise by 8.2 percent this year—the largest increase since 2008—citing a broader security environment marked by rising conflict. These moves point to a shift toward a more self-reliant defense posture, reflected in expanded investment in advanced weapons systems and related capabilities. Debate over indigenous nuclear options—once a strategic taboo—has entered the political mainstream, reflecting growing uncertainty about the credibility of US extended deterrence. Interest in nuclear-powered submarines and other advanced strategic assets further points to a broader shift toward enhancing self-reliant deterrence.

North Korean provocations have not restrained South Korea. Instead, they have tended to reinforce these dynamics. Each episode of pressure adds weight to arguments in Seoul for greater autonomy, firmer deterrence, and less tolerance for ambiguity.

When Burden-Shifting Fuels an Arms Race

The absence of North Korea from the US NSS does not diminish the need for clear signaling on the Korean Peninsula. If anything, it heightens the importance of how Washington communicates its strategic intentions. Burden-shifting to allies without clear guardrails is accelerating regional arms competition.

In addition to the NSS, recent US actions on the global stage—ranging from military responses surrounding the Venezuela crisis to statements suggesting that military options remain under consideration in relation to Greenland—have reinforced these dynamics by contributing to perceptions that US strategic decision-making is becoming less predictable and more willing to rely on the use of force.

As these perceptions evolve, US global strategy is shaping security choices on both sides of the Peninsula. For Pyongyang, the recent US military actions are likely to have reinforced a long-standing belief that continued military strengthening offers the most reliable guarantee of regime survival. However, South Korea is also placing greater emphasis on defense buildup, expanded strike capabilities, and more unilateral forms of preparedness, given the current geopolitical trends.This trajectory could entrench a pattern of sustained arms competition on the Korean Peninsula, increasing the risk of crisis instability. This dynamic is especially pronounced around sensitive flashpoints such as the NLL and the KADIZ. In these areas, North Korea may be increasingly incentivized to test and reshape the military status quo, raising the likelihood that South Korean responses—ranging from preemptive measures to more forceful retaliation—move onto more dangerous and destabilizing paths.

What Washington Must Stop Assuming

At the core of this problem lies a set of assumptions that no longer hold. Washington can no longer treat strategic ambiguity as a substitute for active crisis management on the Korean Peninsula. Nor can it assume that delegating deterrence to allies will automatically produce stability, or that North Korea’s provocations can be indefinitely absorbed without structural consequences.

Burden-shifting is not inherently destabilizing. But absent clear guardrails, it creates incentives for risk-taking by all parties—encouraging Pyongyang to test boundaries, Seoul to harden its responses, and regional powers to prepare for spillover.

South Korea cannot be expected to indefinitely absorb gray-zone coercion while maintaining political restraint. As military capabilities expand, domestic tolerance for ambiguity is likely to diminish, narrowing the space for calibrated responses. Measures that once relied on signaling and patience now carry a greater risk of escalation—dynamics that neither Seoul nor Washington may be able to fully control.

Managing this environment does not require restoring US primacy on the Peninsula, but it does demand greater discipline in signaling. Credible intentions must be communicated through consistent senior-level messaging, allied coordination, and crisis-management–focused military posture, with particular clarity around red lines in disputed maritime and airspace zones. Without this, continued pressure to shift burdens is likely to invite further military adventurism. On a peninsula increasingly shaped by arms racing, alliance asymmetries, and great-power entanglement, the costs of miscalculation are set to rise.