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The U.S. National Security Strategy (NSS) and Possible Shifts in Japan's Security Posture |
| January 15, 2026 |
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Kitae LEESenior Research Fellow, Sejong Institute | ktleekorea@sejong.org
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The National Security Strategy (hereafter "NSS"), released by the second Trump administration under President Donald J. Trump on December 4, 2025, is regarded as a document that marks a critical turning point for the security order across the Indo-Pacific region. The NSS puts forward a collective "deterrence by denial" strategy, centered in particular on deterrence in Taiwan and along the First Island Chain, as the core pillar of its approach to the Indo-Pacific. The release of the NSS is considered a symbolic event declaring not merely a shift in strategic orientation for a particular region, but a broader shift in America's global strategic priorities from a Europe-centered order to an Asia-centered one. The NSS is also functioning as a "strategic mirror" for Japan, calling on Japan simultaneously to structurally realign the U.S.-Japan alliance and redefine its own national security identity.
The NSS sends a clear message: the durability of the U.S.-Japan alliance depends not on diplomatic assurances alone, but on Japan's willingness to back its commitments with tangible action, specifically by building up its defense capabilities and taking on greater autonomous responsibility. Japan has welcomed the NSS as a chance to reaffirm the alliance's strategic value, but the document also places Japan in a difficult position, requiring it to chart a new course in response to Washington's insistence on "burden sharing" and expanded self-reliance. The upshot is that Japan has doubled down on the "proactive pacifism" agenda it has pursued for over a decade, accelerating its efforts to establish itself as a linchpin of the U.S.-led Indo-Pacific strategy. -
In Japan, the NSS is widely seen as the Trump administration's latest move to formalize the "conditional" nature of the alliance. Rather than invoking the rhetoric of a "values-based alliance," the document reframes the concept of alliance around partnerships that deliver tangible benefits to U.S. security and economic interests. For Japan's government and policy elites, this shift signals the end of the "postwar alliance order." Put simply, it marks a turning point at which the United States no longer offers military protection as a "public good," but has moved toward a transactional alliance framework built on reciprocal contributions.
That said, Japan's policy community has largely resisted the temptation to write off this shift as a simple "return to isolationism." If anything, the dominant view is that the NSS makes considerable sense as a push for qualitative alliance strengthening and greater "role clarity."1) This reflects a broader reality: Japan has already grown comfortable with a burden-sharing structure within the alliance, having navigated a succession of policy changes since the Abe (安倍晋三) government, among them the authorization of collective self-defense and the revision of the Three Principles on Transfer of Defense Equipment.
Even so, the NSS represents a new litmus test for Japan, demanding that it move beyond the role of a supporting actor and demonstrate the political and military will needed to establish itself as an equal and central pillar within the U.S. strategic framework. This debate is very much alive in Japan's media and security expert circles. The Yomiuri Shimbun argued in response to the NSS that "Japan needs to deepen U.S.-Japan cooperation to help the United States maintain its influence,"2) while the Asahi Shimbun pushed back, arguing that "simply following a United States that pursues its own interests at the expense of international cooperation is inconsistent with Japan's own strategy."3) Those who place a premium on the U.S.-Japan alliance view the NSS as Washington's formal stamp of approval on the trajectory set by Japan's three security documents, the National Security Strategy, the National Defense Strategy, and the Defense Buildup Plan, and see it as an opening for Japan to cement its status as an indispensable partner in the alliance through higher defense spending and an expanded role. Critics, however, paint a different picture, characterizing the NSS as a textbook case of a "transactional alliance" that saddles allies with excessive defense spending obligations and pressure to buy American weapons, and warning that Japan risks being reduced to a subordinate player in U.S. strategy.4) The bottom line is that Japan remains divided over whether the alliance is fundamentally about "cooperation" or "coercion," and this fault line is likely to run directly through future debates over the revision of Japan's security documents in response to the NSS.
Meanwhile, the debate over NATO-style nuclear sharing resurfaced in Japan in the wake of the Russia-Ukraine War that began in 2022. Former Prime Minister Abe's remarks on NATO-style nuclear sharing in particular deepened the divide between those calling for nuclear sharing discussions and those insisting on maintaining the Three Non-Nuclear Principles,5) and while the Kishida (岸田文雄) government officially opposed nuclear sharing discussions, the release of the NSS has prompted some conservatives to once again push for broader debate on the nuclear question. As a result, the NSS's call for a capability-based alliance and enhanced deterrence is being used by some Japanese conservatives to justify calls for revisiting the country's "deterrence portfolio, including the nuclear option." -
Another core element of the U.S. NSS is the substantive rebuilding of the First Island Chain's defensive architecture. This strategy envisions a defensive perimeter linking Japan, Taiwan, the Philippines, and the South China Sea as a kind of forward deterrence network, and emphasizes that allies must serve as active components of deterrence. Notably, the NSS's acknowledgment that U.S. forces alone would struggle to repel a regional invasion has also been interpreted as a strategy of U.S.-led "outsourcing of deterrence."6) Japan has long leveraged this recognition to justify a range of policy initiatives, including its target of defense spending at two percent of GDP, the acquisition of counterstrike capabilities, the strengthening of integrated command and control systems, and the modernization of missile defense capabilities.
In line with this, the NSS explicitly states that "allies must serve as active components of forward deterrence" along the First Island Chain. Japan has already taken steps to align itself with the NSS's requirements for clarity in roles, missions, and capabilities. Most notably, it established the Japan Joint Headquarters (JHQ) in March 2025, strengthening its joint command and intelligence-sharing structure with U.S. forces in Japan.7) In tandem with the evolving role of U.S. forces in Japan, Japan is also reinforcing its defense of the Nansei (南西) Islands, reorganizing U.S. Marine Corps regiments in preparation for a Taiwan contingency, expanding jointly used bases between Japan and the United States, and enhancing joint postures in the space, cyber, and electronic warfare domains. This marks a shift in the role of U.S. forces in Japan from simple stationing to "joint deterrence and joint operations," with the JHQ serving as an institution that simultaneously embodies Japan's autonomy and its contributions to the alliance.
Historically in Japan, increases in defense spending were constrained by the symbolic limits of its postwar identity as a "peace-state." In the 2020s, however, the convergence of China's military buildup, North Korea's increasingly sophisticated missile threats, and Russia's growing military activities in Northeast Asia has driven a fundamental shift in perception, with defense spending transitioning from an "exceptional measure" to a "prerequisite for sustainable security management." The concrete framework for defense cooperation laid out in the NSS thus provides Japan with the institutional justification to push toward defense spending above two percent of GDP, while also supporting the effective implementation of the U.S.-Japan Defense Cooperation Guidelines.
The Japanese government is also actively interpreting the NSS's concept of a "capability-based alliance" and deploying it as a tool to build domestic public support. In particular, the concept of "joint deterrence" serves as a means of establishing both the legitimacy and moral foundations of defense policy within Japanese society. -
Nevertheless, the NSS's treatment of Russia and North Korea has given Japan cause for concern. The document's characterization of Russia as a subject of "reestablishing strategic stability" departs from the conventional designation of Russia as an "explicit adversary," which Japan reads as something closer to "strategic indulgence." Japan worries that language that appears to tacitly condone Russia's invasion of Ukraine could embolden further attempts by China or North Korea to alter the status quo in Northeast Asia. Of particular concern is the potential for Japan's strategic vulnerabilities to deepen in relation to the defense of northern Hokkaido and the Northern Territories (the Kuril Islands).
The fact that North Korea has been significantly downplayed in the NSS has also generated frustration among Japanese practitioners.8) Japan had hoped the NSS would reaffirm its commitment to North Korean denuclearization, but with the document's focus squarely on China deterrence and energy and technology strategy, coverage of North Korea was reduced to the level of a "regional concern."
As a result, a growing consensus is forming within Japan that the NSS is effectively a "China-focused strategic document." This imbalance has reinforced the need for Japan to take a more independent approach to North Korea, even as it maintains the framework of ROK-U.S.-Japan trilateral cooperation. Japan is likely to move toward concretizing its vision of a "Japan-style extended deterrence strategy model" tailored to countering North Korea's advancing nuclear capabilities. -
The aspect of the NSS that brought Japan the greatest sense of relief was the Trump administration's strong language stating that it would "not tolerate any attempt to change the status quo in the Taiwan Strait by force."9)
By opening the door to actual involvement in Taiwan's defense, the NSS has directly aligned with Japan's defense plans for the Nansei Islands.
Japan has already formalized such a situation as inseparable from its own security by including a Taiwan contingency within its concept of "multi-domain integrated defense" since 2022. In particular, the Japanese government actively cites the "joint defense of the First Island Chain" concept contained in the NSS, emphasizing that the U.S.-Japan alliance must evolve beyond simple bilateral deterrence into a structure equivalent to a combined operations framework.10) This perception is being used as strategic language to justify specific defense policies, such as expanding Japan's counterstrike capabilities, deploying ship-launched cruise missiles, and strengthening satellite surveillance systems and unmanned aerial assets.
Japan also recognizes that these changes matter not only for military deterrence but for "political trust-building" as well. With the Trump administration signaling a clear willingness to engage on the Taiwan issue, Japan is stepping up its efforts to institutionalize a Taiwan contingency response framework within the operational framework of the U.S.-Japan alliance.
Japan is actively interpreting the NSS as an external factor that strengthens the coherence of its own security policy. The Indo-Pacific-focused strategy presented in the NSS aligns closely with the ideological and structural framework outlined in Japan's three security documents released in December 2022. Japan views this alignment as an "alignment of vision," assessing that it has created an environment conducive to securing both the domestic political legitimacy of its defense buildup and broad public consent.
Furthermore, from an economic security perspective, the NSS presents Japan with three structural opportunities.11) The first is expanded energy cooperation. The NSS's proclamation of "energy dominance" while cautioning against the "ideologization of climate change" provides Japan with economic and technological space to re-engage with the U.S. energy production and supply base. Japan's LNG shipping, nuclear safety technology, and renewable energy hybrid storage systems are seen as prime areas for deepening strategic complementarity between the two countries.
The second is cooperation in the defense and aerospace industries. The "Reviving our Defense Industrial Base" provision outlined in the NSS12) aligns with Japan's defense industry revitalization project. Major manufacturers such as Mitsubishi Heavy Industries and Kawasaki Heavy Industries are already expanding their joint MRO (maintenance, repair, and overhaul) cooperation frameworks with the United States, and joint development in unmanned aerial vehicles, sensor fusion systems, and satellite-based defense systems is under discussion.
The third is the restructuring of global supply chains. With the NSS identifying access to critical minerals and the securing of semiconductors and battery components as strategic objectives, Japan has emerged as a key partner in building "China-alternative supply chains." Within Asia, Japan is increasingly regarded as an alternative hub that combines financial, technological, and political stability, broadening the reach of Japan's economic security strategy.
Meanwhile, the Takaichi (高市早苗) administration reaffirmed its existing stance of pursuing constructive and stable relations with China, stating at the 2026 New Year press conference that "the door to dialogue with China remains open," while simultaneously strengthening defense capabilities in line with the NSS. In other words, Japan is pursuing a dual-track approach under the NSS: strengthening deterrence and alliance capabilities while simultaneously emphasizing the need for strategic communication and risk management in relations with China. -
The core principle revealed by the NSS is the "commodification of alliance." The Trump administration redefined alliances as conditional contractual relationships through its declaration that "free-riding will no longer be tolerated."13)
Consequently, Japan now faces structural pressure to present concrete "deliverables," such as increased defense spending, weapons purchases, and force integration, to secure the political continuity of the alliance. Within Japan, this trend could lead to a "qualitative strengthening of the alliance," but it also carries the equally real risk of "institutionalized dependency."
Politically, Japan's pursuit of greater strategic autonomy is coming into sharper focus. Under the Trump-style NSS, Japan has come to recognize the need to evolve into an "autonomous ally" capable of sustaining its own deterrence even when U.S. commitment is limited or uncertain. Since the launch of the Takaichi administration in October 2025, calls for building tangible autonomous defense capabilities have been gaining traction within Japan, encompassing proposals to expand the Self-Defense Forces' force structure, explore the introduction of nuclear-powered submarines, and extend missile ranges.
Following the Russia-Ukraine War, debate over nuclear sharing began within Japan. After the launch of the Takaichi administration in 2025, discussions on the possibility of revising the Three Non-Nuclear Principles have entered the public sphere. As the role demanded of Japan by the NSS, namely First Island Chain deterrence and a capability-based alliance, grows stronger, Japan's conservative camp is increasingly advocating for partial adjustments to the Three Non-Nuclear Principles and a review of nuclear sharing. However, resistance from domestic public opinion and existing norms remains significant.14) Discussions on introducing nuclear-powered submarines also began within the context of Japan's demand for "First Island Chain denial deterrence" under the NSS. Japan has begun exploring the introduction of nuclear-powered submarines and their interoperability, referencing models such as AUKUS. However, short-term realization is difficult due to technological and financial burdens, domestic anti-nuclear sentiment, and issues regarding the allocation of strategic assets within the United States. Currently, the discussions remain at the level of "review and research."
This broader push toward self-reliant defense is forming a new equilibrium within Japan's security strategy, one that preserves the three foundational pillars that have guided Japanese security policy since 2013, namely ① strengthening the U.S.-Japan alliance, ② enhancing its own defense capabilities, and ③ expanding regional networks, while placing greater weight on "securing strategic autonomy" among these pillars.
Ultimately, the direction of the demands presented by the NSS, including increased defense spending by allies, joint defense of the First Island Chain, a capability-based alliance, and deterrence against China, aligns closely with the direction pursued by the Takaichi administration. This includes reviewing defense spending increases to over two percent of GDP, enhancing counterstrike capabilities, considering long-range missiles and nuclear-powered submarines, pushing for revisions to the three security documents, and expressing a willingness to engage in the event of a Taiwan contingency.
Meanwhile, discussions among some hardliners within the Takaichi administration regarding nuclear sharing and a revisitation of the Three Non-Nuclear Principles may conflict with the "extended deterrence + non-proliferation" framework preferred by the United States. Furthermore, the NSS's relatively low emphasis on Russia and North Korea and its stress on "strategic stability" remain a source of friction with the Takaichi administration's concerns regarding the Northern Territories and the North Korean nuclear threat.
Ultimately, the Takaichi administration is expected to pursue a multi-layered strategy along several interconnected tracks: strengthening defense and expeditionary capabilities, including counterstrike and long-range strike capabilities, in the Nansei Islands in preparation for a Taiwan contingency; reinforcing integrated command through the establishment of the JHQ and enhancing combined readiness with U.S. Forces Japan; expanding U.S.-Japan coordination across economic security domains, including supply chains, technology, the defense industry, and energy; and advancing a dual-track strategy toward China of "firm deterrence + maintaining dialogue channels." -
The Takaichi administration has already formalized its intention to revise the three security documents, with 2026 set as the target. The draft revisions currently under discussion, led by the LDP's Security Research Council and Defense Division, are broadly divided into two camps.
The first is the "non-revision" camp, which holds that since the 2022 three security documents already encompass the objectives of addressing threats from China, North Korea, and Russia; securing counterstrike capabilities; and increasing defense spending, there is little practical benefit in wholesale adoption of the U.S. NSS. Furthermore, if the NSS's language on military engagement related to Taiwan is directly incorporated into Japan's strategic documents, there is a risk of creating interpretive tensions between Article 9 of the Constitution and the security legislation.
The second is the "pro-revision" camp, which holds that some degree of policy realignment is unavoidable in order to reflect the shifting international order and the rise of a Trump-style alliance paradigm. Proponents of revision argue that Japan's strategic documents should be reframed around "policy realism," including expanding defense spending to 3.5 percent of GDP, partially relaxing the Three Non-Nuclear Principles, and strengthening long-range counterstrike capabilities.
At the heart of this debate lies the question of "to what extent Japan should strategically accommodate the U.S. NSS." Consequently, the Japanese government is highly likely to pursue its NSS revision not merely as a policy adjustment, but as a "reframing of its political messaging." Ultimately, the process is expected to converge on an explicit articulation of a balance between "strengthening the U.S.-Japan alliance and securing Japanese-style autonomy." -
The U.S. NSS makes clear that "shared values" alone are no longer sufficient for allies, and that what is required is the "capability" to make tangible contributions to U.S. security and economic interests. For Japan, this represents both a challenge and an opportunity for strategic transformation. While it will entail short-term burdens in terms of fiscal resources, military buildup, and public opinion, it also provides a new structural opportunity for Japan to establish itself as an "indispensable ally" over the medium to long term.
Ultimately, the Trump administration's NSS introduced a new standard of a “capable ally” within the Indo-Pacific order, and accordingly, Japan's security strategy is moving toward a new equilibrium characterized by the simultaneous strengthening of the alliance and the enhancement of strategic autonomy.
However, to transform these opportunities into tangible strategic assets, Japan must carefully manage the “balance between alliance dependence and autonomy.” Japan is actively implementing an integrated security strategy that combines security and economic policy, converting defense industrial, energy, and technological cooperation from mere costs into engines of growth. This transformation extends beyond Japan’s defense policy and will generate cascading effects across regional strategic dynamics, including trilateral cooperation, strategic competition among South Korea, China, and Japan, and the QUAD security framework.
In this regard, the U.S. NSS announcement carries significant strategic implications for South Korea. As Japan elevates its defense enhancement trajectory to a qualitatively higher level within the framework of the U.S.-Japan alliance, South Korea must likewise maintain the ROK-U.S. alliance as its central pillar while simultaneously expanding its autonomous strategic options through multilateral security cooperation with Europe, India, and Southeast Asia, as well as through defense export-oriented initiatives. Based on these implications, two specific directions for future ROK-Japan cooperation are identified below.
First, there is the need for ROK–Japan coordination on North Korea policy and extended deterrence. Through the ROK–U.S.–Japan Extended Deterrence Consultative Mechanism, it is necessary to design a cooperative framework that links Japan’s discussions on a “Japan-style extended deterrence model” with the ROK’s debates on the rotational deployment of U.S. strategic assets and the nuclear umbrella, in order to prevent the emergence of a “double standard.” In addition, to ensure that the ROK’s position is reflected in future discussions on linking the U.S.–Japan National Security Strategy frameworks, the ROK could propose the development of joint scenarios addressing North Korea–Russia threats in the context of ROK–U.S.–Japan defense and foreign affairs (2+2) meetings or working-level consultations.
Second, it is necessary to promote minilateral cooperation, such as ROK–U.S.–Japan–Australia, amid changes in Indo-Pacific strategy. The ROK should explore areas of cooperation in which it can participate within ROK–U.S.–Japan–Australia joint exercises and information-sharing frameworks, including maritime domain awareness, cyber, and space. In addition, joint projects and consortia could be considered to ensure that Japan’s strategies in defense industry, energy, and supply chains, and the ROK’s strategies in defense exports, batteries, and semiconductors, evolve into a “complementary division of labor” rather than a competitive relationship.
| Japan's Perceptions of the U.S. NSS Release
| Justifying Defense Spending Increases and the Logic of Strengthening Deterrence
| Japan's Frustrations with the NSS: Russia and North Korea
| Deepening of Japan's Security Strategy and Opportunities in Economic Security
| The Risks of a Transactional Alliance and Japan's Autonomy Dilemma
| Linking the NSS to Future Revisions of Japan's Three Security Documents
| Policy Implications
1) “米安全保障戦略に日本の外務省幹部「気になるところある」 米中接近の不安, 解消されず,” 『産経新聞』 2025年12月13日.
2) “米国家安保戦略 「自国第一」では中露を利する,” 『読売新聞』 2025年12月9日.
3) “(社説) 米安保戦略 利己に走る大国を憂う,” 『朝日新聞』 2025年12月11日.
4) Jesse Johnson, “Trump strategy demands more of Japan as U.S. unveils ‘burden-sharing network’,” The Japan Times, December 6, 2025 <https://www.japantimes.co.jp/news/2025/12/06/japan/politics/japan-us-national-security-strategy/> (검색일: 2026.1.2.).>
5) Tanida Kuniichi, “Next Steps in Japan’s Nuclear Sharing Debate,” nippon.com, June 6, 2022 <https://www.nippon.com/en/in-depth/d00809/> (검색일: 2026.1.2.).
6) The White House, “National Security Strategy of the United States of America,” November 2025, p. 24. <https://www.whitehouse.gov/wp-content/uploads/2025/12/2025-National-Security-Strategy.pdf> (검색일: 2026.1.2.).
7) Jesse Johnson, “Trump strategy demands more of Japan as U.S. unveils ‘burden-sharing network’.”
8) “(主張) 米安保戦略発表 台湾有事阻む決意示した,” 『産経新聞』 2025年12月9日.
9) The White House(2025), p. 23.
10) “Our allies must step up and spend-and more importantly do-much more for collective defense”, The White House(2025), p. 24.
11) 実業之日本フォーラム編集部, “米国「国家安全保障戦略」, 2022年版と最新版を読み比べて見えてくる日本の好機,” 2025.12.08., <https://forum.j-n.co.jp/narrative/8943/> (검색일: 2026.1.2.).
12) The White House(2025), p. 14.
13) “ヘグセス米国防長官, 日本などに「もはやただ乗りは許さない... 防衛支出の大幅増を改めて要求,” 『読売新聞』 2025年12月7日.
14) Yuki Tatsumi·Pamela Kennedy·Kenji Nagayoshi, “Japan’s Strategic Future and Implications for the US-Japan Alliance,” Stimson Report, February 28, 2024 <https://www.stimson.org/2024/japans-strategic-future-and-implications-for-the-us-japan-alliance/> (검색일: 2026.1.2.).
※ The contents published on 'Sejong Focus' are personal opinions of the author and do not represent the official views of Sejong Institue
