File
|
Implications of the U.S. National Security Strategy (NSS) and Policy Considerations for the Republic of Korea |
| December 9, 2025 |
-
Beomchul ShinPrincipal Research Fellow, Sejong Institute | bcshin@sejong.org
- The Trump administration has released its National Security Strategy (hereafter “NSS”). Grounded in President Trump’s America First doctrine, the new NSS underscores the need for cooperation with allies and partner countries while emphasizing homeland defense, economic security, and strategic competition with China. With respect to the Korean Peninsula, unlike previous strategies, it does not address the North Korean nuclear issue, thereby placing greater weight on the possibility of dialogue. At the same time, it emphasizes burden sharing and burden shifting with allies and suggests the likelihood that South Korea will be expected to assume a role in deterring China’s military challenges along the First Island Chain. In particular, preparations should be made for the possibility that the United States may raise expectations regarding the regional role of South Korea’s nuclear-powered submarines.
-
NSS 2025 consists of a two-page foreword and twenty-nine pages of main text. It is organized into Chapter 1, What is American Strategy; Chapter 2, What Should the U.S. Want; Chapter 3, America’s Available Means; and Chapter 4, Strategy, which sets forth guiding principles, priorities, and regional approaches.
With respect to strategic orientation, the document adopts an America First framework and contends that previous strategies were insufficiently grounded in geopolitical realities, having been shaped instead by residual Cold War paradigms and ideological predispositions. In this view, earlier approaches failed to advance U.S. national interests effectively. For example, it argues that an expansive commitment to free trade contributed to economic dislocation among the American middle class and promoted initiatives only tenuously connected to core national interests.1)
In defining what the United States should seek, the NSS emphasizes the God given natural rights of its citizens and prioritizes their well-being and interests, placing paramount importance on safeguarding the nation’s survival and safety. To that end, it calls for strengthened border control, reinforced critical infrastructure, a technologically advanced and modernized military, the deployment of a next-generation missile defense architecture referred to as the Golden Dome, and the construction of an innovative, high-productivity economy. It further stresses cooperation with international partners to secure stability in the Western Hemisphere, counter foreign economic coercion, preserve a free and open Indo-Pacific, uphold Europe’s freedom and security, deter hostile actors in the Middle East, and establish U.S. standards in advanced technological domains such as artificial intelligence, biotechnology, and quantum computing.
With respect to the means available to achieve these objectives, the NSS highlights the resilience of the U.S. political system, the scale and innovative capacity of its economy, the strength of its financial architecture, advanced technological capabilities, and superior military power. It also outlines President Trump’s domestic agenda, including measures to enhance competitiveness, advance energy innovation, reindustrialize the American economy, and reinforce supply chain security in support of the middle class.
In what may be considered the strategic core of the document, the NSS articulates principles including a national interest–centered approach, peace through strength, non-interventionism, flexible realism, balance of power, and fairness. It identifies priorities such as ending the era of mass migration, protecting fundamental human rights, and promoting both burden sharing and burden shifting. Among these, economic security receives the most sustained attention, with emphasis on balanced trade, securing access to critical supply chains and essential materials, reindustrialization, revitalizing the defense industrial base, sustaining energy dominance, and preserving leadership in the financial domain.
The final section delineates regional strategies. It underscores overwhelming U.S. primacy in the Western Hemisphere, homeland defense, and the resolution of regional challenges. In the Indo-Pacific, it emphasizes deterring China while preventing escalation and strengthening cooperation with allies and partners. In Europe, it calls for increased defense spending and deeper security cooperation, urging European states to assume greater responsibility while reaffirming the U.S. role in stabilizing Europe–Russia relations. In the Middle East, it stresses countering Iran, advancing regional peace, expanding the responsibilities of regional actors, and safeguarding energy security. In Africa, it highlights not only conflict resolution but also a strategic shift from aid-centered engagement toward partnerships grounded in trade and investment. -
Omission of Detail Due to Brevity
One of the most notable characteristics of the current NSS is its brevity. At only twenty-nine pages, it is significantly shorter than the fifty-five pages of the Trump administration’s first-term NSS and the forty-eight pages of the Biden administration’s NSS, resulting in the omission of more detailed discussions. The most substantial reductions concern the strengthening of U.S. military and diplomatic capabilities. In the first Trump administration, eleven pages were devoted to these areas, outlining directions for enhancing conventional forces, nuclear capabilities, space, cyber, intelligence, and diplomatic capacity. In contrast, the current NSS addresses these domains only briefly within Chapter 2, What Should the U.S. Want, and Chapter 3, America’s Available Means.
As a result, measures to strengthen the capacity of the U.S. executive branch are described in relatively general terms, while greater emphasis is placed on what should be done at the level of external strategy across economic, military, and diplomatic domains. Rather than providing detailed prescriptions for internal bureaucratic reform, the document focuses on outlining strategic direction for homeland defense and for U.S. engagement in the Western Hemisphere, Europe, Asia, the Middle East, and Africa.
A New Structure Grounded in America First
The current NSS is organized around a problem definition rooted in America First. It first identifies perceived shortcomings in prior national security strategies, particularly excessive interventionism and idealistic approaches. It then specifies what policies the Trump administration seeks to pursue and the means required to achieve them, followed by an articulation of guiding principles, priorities, and detailed regional strategies.
This structure differs from the Trump administration’s first-term NSS (2017), which was organized around functional objectives: protecting the American people and homeland and preserving the American way of life; promoting American prosperity; preserving peace through strength; and advancing American influence.2) Similarly, the Biden administration’s NSS (2022) adopted a function-based structure, outlining investments in U.S. strength, global priorities, and regional strategies in sequence.3)
The structure of the current NSS appears intended to underscore the view that U.S. foreign strategy had been moving in the wrong direction. By first identifying perceived strategic errors of the past and then presenting corrective measures, the document frames the Trump administration’s agenda as a course correction. America First serves as the central evaluative standard, and from this perspective, the direction of U.S. external strategy is redefined, resulting in structural differences from previous NSS documents.
Renewed Emphasis on Economic Security
A defining feature of the first Trump administration’s NSS was its emphasis on economic security. The second-term NSS likewise underscores economic security, though with both continuity and divergence reflecting an updated assessment of the challenges facing the United States.
The principal continuity lies in the emphasis on revitalizing the domestic economy. The first-term NSS called for reenergizing the domestic economy, highlighting fair trade, technological innovation, and energy dominance. These themes are reiterated in the current NSS, reflecting continuity in strategic orientation.
At the same time, three notable differences emerge. First, the current NSS places new emphasis on securing stable access to critical supply chains and materials. This shift appears to reflect concerns arising from China’s use of export controls on rare earth elements and other strategic materials. The document states that the United States will strengthen monitoring of supply chains and technological development in order to expand independent and reliable access to critical minerals and related inputs.
Second, the NSS places greater emphasis on reindustrialization to restore domestic industrial capacity. While the first-term NSS addressed domestic economic revitalization, the current document more explicitly highlights the return of industrial facilities to the United States. It signals the use of tariffs as a policy instrument and emphasizes reducing dependence on current or potential adversaries for critical industries and components.
Third, the defense industrial base is framed explicitly within the context of economic security. Although the first-term NSS addressed defense industry issues, it did so under the rubric of peace through strength as part of strengthening domestic capabilities. In contrast, the current NSS categorizes the defense industrial base as a component of economic security, thereby elevating its strategic and economic significance.
Increased Attention to the Western Hemisphere
At the regional level, the prioritization of the Western Hemisphere is particularly pronounced. The NSS references the Monroe Doctrine within President Trump’s strategic outlook and identifies the Western Hemisphere as the foremost regional priority. This represents a marked departure from the first-term NSS, in which the Indo-Pacific, Europe, the Middle East, and South and Central Asia preceded the Western Hemisphere in sequencing. The shift appears to reflect President Trump’s more restrained and regionally focused strategic orientation.
Specifically, the document emphasizes overwhelming U.S. primacy in the Western Hemisphere and the necessity of homeland defense. It suggests a potential realignment of global force posture, indicating that deployments in regions deemed peripheral to core national interests may be reduced. At the same time, it underscores the roles of the U.S. Coast Guard and Navy in strengthening enforcement against illegal immigration and narcotics trafficking, pledging to secure the border, defeat drug cartels, and, if necessary, employ lethal military force where law enforcement proves insufficient.4)
The NSS also outlines efforts to reinforce cooperation with Western Hemisphere states through diplomacy and economic engagement. This appears aimed at countering certain foreign actors seeking to expand their influence in Latin America. In effect, the strategy signals an intent to prevent states such as China from deepening alignment with countries in the region in ways that would challenge U.S. predominance in the hemisphere.
Beyond the Western Hemisphere, the Indo-Pacific section details various forms of cooperation designed to counter China, while the Europe section addresses Russia and the war in Ukraine at greater length. The China issue will be examined in the following section, and the discussion of Russia is omitted here, as it does not substantially depart from established positions of the Trump administration’s broader foreign policy approach. -
The Absence of Explicit Reference to North Korea’s Nuclear Program Signals Diplomatic Flexibility
The Absence of Explicit Reference to North Korea’s Nuclear Program Signals Diplomatic Flexibility
One notable feature of the current NSS is the absence of explicit reference to North Korea’s nuclear issue in its discussion of the Korean Peninsula. The first-term Trump administration’s NSS addressed the Indo-Pacific region and described the threat posed by North Korea, noting that it was rapidly accelerating its cyber, nuclear, and ballistic missile programs. It warned that a nuclear-armed North Korea could lead to the proliferation of the world’s most destructive weapons.
Similarly, the Biden administration’s NSS emphasized the complete denuclearization of the Korean Peninsula and strengthening extended deterrence in the face of North Korean weapons of mass destruction and missile threats.5) Against this backdrop, the absence of denuclearization language in the current NSS carries analytical significance.
The rationale may be found elsewhere in the document. In Chapter 4, under the section on principles, the NSS articulates flexible realism,6) including a commitment to maintaining good relations with countries whose governing systems and societies differ from ours. In this context, the decision not to single out North Korea’s nuclear program may indicate an effort to preserve diplomatic flexibility. Rather than foregrounding the North Korean threat, the strategy leaves open the possibility of engagement and suggests an intent to manage the issue through dialogue. This posture is consistent with President Trump’s previous willingness to engage Chairman Kim Jong Un and may intersect with anticipated high-level diplomacy, including the President’s planned visit to China in April next year, potentially creating conditions conducive to renewed talks.
Accordingly, the government should pursue close prior coordination with the United States to ensure that any U.S.–North Korea dialogue can serve as a bridge toward inter-Korean engagement. At the same time, it would be imprudent to assume that such dialogue will proceed smoothly. North Korea may seek direct negotiations with the United States while attempting to sideline South Korea in order to shape the strategic environment on the Peninsula to its advantage. Seoul should therefore consistently signal its willingness to engage in inter-Korean dialogue while maintaining sanctions as a source of negotiating leverage. Close coordination with Washington will be essential regarding the timing and conditions for resuming talks with Pyongyang and mechanisms to link U.S.–North Korea engagement with inter-Korean dialogue.
Anticipating Stronger U.S. Expectations for Cooperation in Countering China
The current NSS devotes unusually detailed attention to China. The most extensive discussion concerns economic competition, including commitments to counter unfair trade practices, prevent intellectual property theft and industrial espionage, and eliminate threats to U.S. access to critical minerals. At the same time, the document makes clear that economic measures must be paired with credible deterrence in order to prevent conflict. It emphasizes the strategic importance of the island chains and maritime lines of communication, devoting specific attention to the Taiwan Strait, the First and Second Island Chains, and the South China Sea. Such geographic specificity was largely absent from the first-term Trump NSS and is particularly notable given the overall brevity of the current document.
Of particular significance is the treatment of the First Island Chain, which is closely linked to potential Taiwan contingencies. The NSS states that the United States will build a military capable of denying aggression anywhere in the First Island Chain, while underscoring that this objective will be pursued through collective defense with allies. It explicitly calls on allies to increase both defense spending and operational contributions. In its reference to South Korea, the document emphasizes increasing defense spending with a focus on the capabilities—including new capabilities—necessary to deter adversaries and protect the First Island Chain.7) This language suggests that Washington may seek expanded South Korean participation in regional deterrence efforts.
The joint fact sheet issued following the November 14 U.S.–ROK summit included language implying strategic flexibility and emphasized the conventional deterrent role of U.S. Forces Korea against regional threats. By contrast, the NSS more directly signals expectations regarding South Korea’s potential contribution to the defense of the First Island Chain. This divergence suggests that additional requests beyond prior summit understandings could arise in future alliance consultations. Particular attention should be paid to the reference to new capabilities, which may implicitly include South Korea’s prospective nuclear-powered submarines.
The policy challenge for Seoul is therefore to reinforce alliance credibility while preventing automatic expansion of its military role beyond the Peninsula. A calibrated approach would strengthen alliance coordination, maintain primary focus on deterring North Korea, and clarify the division of labor within the alliance framework.
Positive Signals for Nuclear-Powered Submarine Cooperation, with the Need for Careful Messaging
In this context, the NSS suggests favorable conditions for advancing South Korea’s nuclear-powered submarine program during the Trump administration. The document does not emphasize nonproliferation concerns or the North Korean nuclear issue and highlights defense industrial cooperation with allies. These elements may indicate a more supportive environment for such cooperation. Efforts should therefore be made to formalize understandings at an early stage and to secure U.S. congressional approval where necessary.
At the same time, questions regarding the operational role of nuclear-powered submarines are likely to arise. This issue is consistent with remarks made at the October 29 summit concerning the tracking of submarines operating from the direction of China. The NSS makes clear that while the United States seeks allied cooperation in countering China, it does not advocate direct confrontation. Rather, it emphasizes preventing a large-scale military conflict through credible deterrence. It also suggests that economic and military approaches can operate in combination, forming a virtuous cycle that preserves diplomatic space.
Accordingly, in discussions with the United States, careful coordination and messaging will be required regarding any expectations for a regional role for South Korea’s nuclear-powered submarines. Publicly emphasizing expanded regional missions could generate unnecessary tensions and reduce diplomatic flexibility. It will therefore be important to underscore the strategic linkage between the First Island Chain and the Korean Peninsula theater, emphasizing that a leading South Korean role in deterring North Korea contributes to broader regional stability. Finally, even if differences of view emerge during alliance consultations, they should be managed discreetly. Where negotiations encounter difficulties, priority should be given to securing the capability itself while maintaining alliance cohesion.
| Key Elements of NSS 2025
| Key Characteristics of NSS 2025
| Implications for the Korean Peninsula and Policy Considerations
1) The White House, National Security Strategy of 2025, p. 1. https://www.whitehouse.gov/wp-content/uploads/2025/12/2025-National-Security-Strategy.pdf (Search date: 2025.12.8.)
2) For the first-term Trump administration’s National Security Strategy, see: https://trumpwhitehouse.archives.gov/wp-content/uploads/2017/12/NSS-Final-12-18-2017-0905.pdf (Search date: 2025.12.8.)
3) For the Biden administration’s National Security Strategy, see: https://bidenwhitehouse.archives.gov/wp-content/uploads/2022/10/Biden-Harris-Administrations-National-Security-Strategy-10.2022.pdf (Search date: 2025.12.8.)
4) National Security Strategy of 2025, supra note 1, p. 16.
5) Biden administration, National Security Strategy, supra note 3, p. 38..
6) National Security Strategy of 2025, supra note 1, p. 9.
7) National Security Strategy of 2025, supra note 1, p. 24.
※ The contents published on 'Sejong Focus' are personal opinions of the author and do not represent the official views of Sejong Institue
