Key Elements of the 2026 U.S. National Defense Strategy and Policy Implications

Beomchul SHIN

bcshin@sejong.org

Principal Research Fellow

Sejong Institute

1. Major Elements of the 2026 U.S. National Defense Strategy (NDS)

The National Defense Strategy (2026 NDS), published in January, is the highest-level defense guidance document issued by the Department of War (DoW) to establish defense priorities, resource allocation, and military employment guidelines in order to achieve national security objectives. Typically revised every four years, the NDS operationalizes the National Security Strategy (NSS) issued by the White House from a defense perspective. The 2026 NDS likewise builds upon the guidance set forth in the NSS released late last year and presents the foundational strategic direction for the defense sector.

A. Background and Assessment of the Security Environment

The 2026 NDS criticizes the idealistic approach of previous defense strategies and seeks to advance an America First doctrine grounded in “Flexible Realism.” It argues that over the past several decades U.S. foreign and defense policy, in pursuit of a “rule-based international order,” expended excessive resources on indiscriminate regime change and unproductive nation-building efforts. In this process, the strategy contends, tangible U.S. interests were neglected, U.S. borders were compromised, allies shifted defense burdens onto the United States, and the overall security environment deteriorated.

Within this context, the NDS assesses security vacuums in the U.S. periphery as severe and prioritizes threats to the homeland and the Western Hemisphere. It emphasizes border protection and non-state threats, identifying cross-border narco-terrorists and illegal migration as national security threats. It underscores what has been termed the “Donro Doctrine,” highlighting absolute U.S. primacy in the Western Hemisphere and stressing the need to prevent hostile forces from penetrating strategic chokepoints such as the Panama Canal and Greenland.

At the global level, the strategy identifies China as the central threat, alongside Russia, Iran, and North Korea. China is defined as the most formidable competitor seeking hegemony in the Indo-Pacific. However, rather than unconditional confrontation, the document emphasizes “peace through strength,” while also calling for enhanced military communication to ensure deterrence and prevent miscalculation. Russia is described as a persistent but manageable threat to European security. Iran and the “Axis of Resistance” are characterized as drivers of instability in the Middle East and potential threats to the U.S. homeland. North Korea is identified as a “direct military threat” to U.S. treaty allies South Korea and Japan and as possessing nuclear capabilities capable of striking the U.S. homeland. The NDS describes the North Korean threat as follows:

<The NDS states regarding North Korea>

“The DPRK poses a direct military threat to the Republic of Korea (ROK) as well as to Japan, both of which are U.S. treaty allies. Although many of North Korea’s large conventional forces are aged or poorly maintained, South Korea must stay vigilant against the threat of a North Korean invasion. North Korea’s missile forces are also capable of striking targets in the ROK and Japan with conventional and nuclear weapons as well as other weapons of mass destruction. At the same time, the DPRK’s nuclear forces are increasingly capable of threatening the U.S. Homeland. These forces are growing in size and sophistication, and they present a clear and present danger of nuclear attack on the American Homeland.”

The NDS also identifies “The Simultaneity Problem,” referring to the risk of coordinated actions by multiple adversaries across different theaters. In response, the document emphasizes burden sharing by allies. While the United States concentrates on homeland defense and deterring China, regional allies are expected to assume primary responsibility for addressing local threats, thereby enabling the United States to manage the risks of simultaneous conflicts across multiple theaters.

B. Core U.S. Defense Strategy

The 2026 NDS outlines four core defense strategies. First, ensuring homeland security and maintaining primacy in the Western Hemisphere. The strategy asserts that border security is national security and defines narco-terrorists as tangible military threats. It emphasizes the establishment of a “Golden Dome” for homeland defense and the development of missile defense systems to protect U.S. airspace from missile and drone threats. The document stresses that the United States will not concede access or influence within the Western Hemisphere and specifically identifies control over strategic locations such as the Gulf of America (formerly the Gulf of Mexico), the Panama Canal, and Greenland.

The NDS also underscores modernization of the U.S. nuclear force. In a changing global nuclear environment, it commits to modernizing and adapting nuclear capabilities to strengthen deterrence and escalation management. The strategy further calls for enhanced cyber defense for U.S. military and critical civilian targets, development of additional means to deter or neutralize cyber threats, and continued focus on Islamist terrorist organizations with the capability and intent to attack the U.S. homeland.

Second, deterring China and adopting a “Denial Defense” strategy. While seeking “Stability, Not Confrontation” in relations with China, the NDS emphasizes maintaining balance through “peace through strength.” The concept of denial defense aims to convince adversaries that aggression will yield no gains, thereby deterring attacks at the outset. To this end, the strategy sets forth the following tasks:

■  Maintaining military communication channels to prevent misunderstandings in crises

■ Establishing overwhelming defensive lines by deploying robust denial capabilities within the First Island Chain

■ Expanding the role of regional allies in the Indo-Pacific to strengthen defense capabilities and maintain balance

Third, burden sharing by allies. The strategy introduces what it calls the Hague Summit standard, urging all allies to spend 5 percent of GDP on defense (3.5 percent core military spending plus 1.5 percent security-related expenditures). It calls upon regional allies to assume primary responsibility for deterring major threats: Europe against Russia, the Middle East against Iran, and South Korea and Japan against North Korea. The United States would provide decisive but limited support.

Fourth, strengthening the Defense Industrial Base. The NDS calls for re-shoring strategic industries to rebuild the capacity for rapid, large-scale weapons production on U.S. soil. It assesses current U.S. defense production capacity as insufficient for major war and calls for comprehensive innovation to restore the United States as the “arsenal of democracy.” The strategy emphasizes regulatory reform and private-sector innovation to integrate advanced technologies, including artificial intelligence, into defense production in order to enhance both speed and quality.

C. Overall Assessment of the 2026 NDS

The 2026 NDS reflects strategic restraint based on recognition of the limits of U.S. capabilities. It discourages overextension in global affairs rooted in misjudgments about U.S. power and instead focuses on strengthening military capacity within realistic constraints. Similar to China’s past strategy of strategic patience, it emphasizes accumulating strength to implement “peace through strength.” As a result, the strategy places greater emphasis on increased defense spending and threat management by allies.

This strategic orientation is likely to persist throughout the Trump administration. Rather than active intervention in global issues, the United States is expected to adopt selective engagement. The NDS articulates a vision of “Decent Peace,” pursuing coexistence under balance of power rather than absolute dominance. This reflects the administration’s intention to avoid great-power conflict while securing U.S. security, freedom, and prosperity. It aspires to achieve not a peace that sacrifices national interests, but a “Noble and Proud Peace.”

While U.S. use of military force is expected to remain limited, decisive and technologically advanced capabilities may be employed at critical junctures to maximize efficiency. Operations such as Operation Midnight Hammer against Iran and Operation Absolute Resolve against Venezuela illustrate a preference for limited-risk operations leveraging advanced military power. In such scenarios, allies are expected to play the primary role in initial conflict phases or deterrence, minimizing U.S. exposure and costs.

This strategic orientation is likely to influence U.S. policy beyond the Trump administration. Although the 2026 NDS reflects the priorities of the current administration, it is grounded in a realistic assessment of U.S. military limitations. Unless U.S. power returns to the overwhelming dominance of the Cold War era, flexible realism and selective engagement are likely to continue. Demands for increased allied defense spending and greater regional responsibility will persist, as the United States seeks to reduce its burdens and concentrate on strengthening key capabilities necessary to prevail in great-power competition. Whether “Decent Peace” or a “Noble and Proud Peace” can be realized in the harsh realities of international politics, however, remains uncertain.

2. Implications for the Korean Peninsula

A review of the 2026 NDS indicates that the United States places primary emphasis on homeland defense and that North Korea’s relative priority has declined. At the same time, the strategy calls for increased burden sharing by allies and assigns primary responsibility for regional threats to those allies themselves. As a result, the following implications for South Korea’s defense posture are likely.

First, increased defense spending. The United States is pressing for a NATO-style benchmark of defense expenditures amounting to 5 percent of GDP by 2035 (3.5 percent core military spending plus 1.5 percent security-related expenditures). Fortunately, South Korea’s commitment—reflected in the Joint Fact Sheet issued following last November’s summit—to allocate 3.5 percent of GDP to defense may be deemed sufficient. Nevertheless, preparations are required in case the United States raises issues related to the purchase of USD 25 billion in U.S. weapons systems and the provision of USD 33 billion in support for U.S. Forces Korea (USFK) stationing costs, as referenced in the same document.

Second, negotiations with North Korea. The reduced priority assigned to the North Korean nuclear issue raises the possibility that the United States may shift toward managing, rather than fully resolving, the North Korean nuclear problem. Accordingly, in addition to leading efforts to strengthen deterrence against North Korea, South Korea should leverage Washington’s “flexible realism” and coordinate closely with the United States to explore avenues for reopening dialogue with Pyongyang.

Third, the need to reinforce deterrence against North Korea. The United States has indicated that allies will serve as the primary agents of their own defense, with the United States providing support that is “decisive but more limited.” This places greater responsibility on South Korea to assume primary responsibility for deterring North Korea’s conventional threats. In particular, capabilities in artificial intelligence, cyber, space, and unmanned systems should be prioritized and fielded at an accelerated pace.

Fourth, strengthening extended deterrence. The concept of “extended deterrence” is no longer explicitly articulated in the 2026 NDS and appears to have been subsumed under the notion of “decisive but more limited support.” Even if “decisive support” includes nuclear deterrence, the provision of advanced conventional capabilities and missile defense assets—traditionally associated with extended deterrence—may become more constrained. To ensure the continuity and credibility of extended deterrence commitments, mechanisms such as the Nuclear Consultative Group (NCG) should be utilized proactively.

Fifth, addressing the issue of strategic flexibility. Given the “Simultaneity Problem” highlighted in the NDS, the United States is likely to intensify its calls for strategic flexibility in the deployment and use of U.S. forces, including those stationed in Korea. Washington may seek greater flexibility to respond simultaneously to contingencies involving North Korea and China. In line with last November’s Joint Fact Sheet, follow-on discussions and higher-level reporting will be unavoidable. South Korea must respond prudently to such demands while ensuring that alliance readiness to deter North Korean threats is not undermined.

Sixth, potential changes to U.S. Forces Korea. To address simultaneous threats, the United States is likely to adjust the force structure of USFK. The NDS refers to U.S. interests in “modernizing force posture” on the Korean Peninsula. Currently centered on Army units, USFK may be restructured toward a multi-domain configuration encompassing naval, air, space, and cyber capabilities. Close prior coordination will be essential to prevent any capability gaps in deterrence against North Korea during this transition.

In addition, South Korea should strengthen bilateral defense industrial cooperation with the United States, expand opportunities for defense exports to the U.S. market, and ensure that U.S. interest in South Korea’s nuclear-powered submarine program does not diminish. Notably, the 2026 NDS is silent on AUKUS, suggesting a possible decline in U.S. focus on providing nuclear-powered submarines to Australia. The absence of explicit reference to South Korea’s program may be understood in the same context. Accordingly, it will be necessary to establish a consultative framework at an early stage, pursue a special agreement, and secure passage through the U.S. Congress.

3. Policy Recommendations

First, the establishment of a comprehensive high-level consultative mechanism to address alliance issues is necessary. Although various bilateral military consultative bodies exist, none is well-suited to address the full spectrum of emerging issues in an integrated manner. The Korea-U.S. Integrated Defense Dialogue (KIDD), while a senior-level policy forum co-chaired at the deputy assistant secretary level, is limited in scope and not designed to address issues such as nuclear-powered submarines. The NCG, though also a high-level mechanism, is confined to extended deterrence matters. The annual Security Consultative Meeting (SCM), while ministerial-level, is limited to periodic engagements and lacks the flexibility required for timely resolution of ongoing issues.

Therefore, a new high-level consultative body involving the Presidential Office and the White House, along with key officials from relevant ministries and agencies, should be established at an early stage. The November Joint Fact Sheet already specifies a consultative body on shipbuilding cooperation. It also references the creation of a vice-ministerial-level mechanism to implement agreements related to investment in the United States, extended deterrence, nuclear cooperation, and nuclear-powered submarines. However, a vice-ministerial channel may be insufficient to advance key priorities from South Korea’s perspective.

Accordingly, even a small, tightly structured consultative group including the Presidential Office and the White House would be appropriate to address alliance issues in a timely and effective manner. This body should be empowered to coordinate on matters requiring whole-of-government cooperation, including strategic flexibility of USFK, bilateral defense industrial and nuclear cooperation, and the nuclear-powered submarine program. The precedent of the NCG’s establishment—led directly by the Presidential Office in coordination with the White House—should be taken into account.

Second, the next summit should articulate a renewed vision for the future of the alliance. The 2026 NDS represents a significant shift in U.S. strategic posture, warranting the formulation of a new alliance vision at the leaders’ level. A joint declaration outlining a sustainable future-oriented alliance could provide a framework for addressing pending issues. As the 2023 Washington Declaration elevated the level of the alliance, a new vision statement could create an opportunity to resolve outstanding matters through the process of negotiation.

Such a vision should incorporate the United States’ emphasis on flexible realism, “decent peace,” and primary responsibility for allies, while clearly defining the scope of “decisive support” required by South Korea and detailing concrete areas of bilateral defense industrial cooperation. At the same time, the potential for excessive demands from the Trump administration must be considered. The drafting process should proceed cautiously and in a manner that helps remove obstacles to securing nuclear-powered submarines.

Assigning the task of drafting the alliance’s future vision to the aforementioned high-level consultative body would be appropriate. A small task force composed of key personnel from the Presidential Office and relevant ministries could complete this work within five to six months through close coordination. Simultaneously, cooperation with research institutions and academia should be pursued to disseminate related concepts and identify additional initiatives necessary for sustainable alliance development. In this context, bilateral public diplomacy—recently in decline—should also be revitalized, as transactional diplomacy under the Trump administration risks weakening the identity and societal foundations of the alliance.

Third, U.S. strategic documents should be leveraged in the formulation of South Korea’s own strategic framework. The current administration is expected to publish a new National Security Strategy and National Defense Strategy in the near future. These documents should present realistic and actionable responses to the evolving security environment. Rather than adopting overly ambitious or idealistic approaches, elements of flexible realism should be incorporated.

By clearly articulating its assessment of the security environment and strategic tasks, the government can present South Korea’s position internationally while fostering domestic consensus. In particular, strategy formulation must reflect the evolving security environment surrounding the Korean Peninsula. If the United States is calling for a fundamental transformation of alliances, South Korea must likewise adopt transformative thinking.

Core concepts should include self-reliance, strategic autonomy, transition to a technologically advanced “smart military” prepared for future warfare, and a focus on crisis management and threat reduction. While it may not be necessary to replicate the clarity of U.S. strategic documents, South Korea’s own documents should prioritize substantive solutions to real challenges over policy messaging.

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