[New Year Special Commentary Series] ⑧ US-China Military Security Strategy Changes in 2026 and South Korea's Defense Strategy

1. The Fear of a 'New Acheson Line'

The first year of a potential second Trump administration in 2025 was a period of self-negation for the United States, which had built the post-World War II order. As voices within the US policy community grew louder in support of a security strategy that shifts the forward defense role to allies like Japan, South Korea, and Taiwan, and withdraws main US forces beyond the second island chain, based on 'America First' and the principle of engaging only in matters concerning core interests (Kim Yang-gyu, 2025/09/16), concerns spread in South Korea that the US might draw a second Acheson Line (JoongAng Ilbo, 2025/04/01; Lee Baek-soon, 2025/10/22). These concerns stem from the experience of the Korean War, which broke out less than six months after Secretary of State Dean Acheson declared in January 1950 that South Korea was excluded from the US defense perimeter in the Far East. There was suspicion that the move to demand allies increase defense spending to around 5% of their GDP and expand the strategic flexibility of US Forces Korea was, in fact, groundwork to exclude the Korean Peninsula from America's core interests.

Amidst this, at the APEC summit in Gyeongju on November 15, the Trump administration "approved" the construction of a nuclear-powered submarine (SSN), a project that had been frustrated for over 30 years, and officially supported expanded uranium enrichment and spent nuclear fuel reprocessing rights, leading newspaper headlines to be filled with expressions of "diplomatic triumph." Amidst extreme swings between fear and euphoria, the Trump administration's "National Security Strategy (NSS)" for its second term was released on December 5. This time, the fact that North Korea was not mentioned even once in the strategy document amplified voices questioning whether the Korean Peninsula had been excluded from America's strategic priorities (Lee Yu-mi, 2025/12/06).

Considering the excessive flexibility and transactional approach shown by the Trump administration over the past year, the security environment on the Korean Peninsula that South Korea will face in 2026 is expected to be challenging. What drives the Trump administration's choices, which advocate for an exclusive US sphere of influence in the Western Hemisphere, a balance of power against China in the Indo-Pacific, and a transactional approach through negotiation with Russia in Europe (Jeon Jae-seong, 2026/01/02)? In what direction will the US defense strategy for 2026 proceed? What defense strategy is China pursuing, and what will the military order in the Western Pacific look like when the visions of these two superpowers converge? Consequently, what are South Korea's defense strategy challenges for 2026, and what preparations are necessary?

2. Changes in US Defense Strategy: Pursuing 'Peace Through Overwhelming Strength' Amidst the 'End of the Unipolar Era'

As emphasized in the recently released NSS, strategy is defined as "a concrete and realistic plan that connects goals and means," and its core task is to "evaluate, classify, and prioritize." For this reason, the NSS, including President Trump's foreword, repeatedly and strongly conveys a sensitive awareness of priorities throughout the document (Whitehouse 2025). In discussions regarding the defense strategy of the Trump administration's second term, which places national interests at the forefront, the question 'What is most important to the United States?' has been consistently raised throughout the past year, even before the NSS was released.

(1) Background of Strategic Reassessment: The 'Lippmann Gap' and the Prioritization Debate

The first person to clearly articulate this issue was Elbridge Colby, the Assistant Secretary of Defense for Strategy, Plans, and Capabilities nominee. In his confirmation hearing before Congress on March 4, 2025, Colby pointed to the mismatch between a nation's foreign policy goals and the resources and political will available to achieve them—the "Lippmann Gap"—arguing that the United States should not respond to every threat globally. Instead, he emphasized the need to (1) concentrate available resources on securing denial capabilities in the Indo-Pacific to counter China's challenge, while urging allies to pay more for their own defense and share responsibility, and (2) prioritize homeland defense and innovation in the defense industrial base.

Meanwhile, Dan Caldwell, former senior advisor to Secretary of Defense Pete Hegseth and reportedly involved in preparing the US National Defense Strategy (NDS) alongside Colby, argued that the survivability of US forces within the first island chain has drastically decreased due to the advancement of China's anti-access/area denial (A2/AD) capabilities. This is not a new assertion; by the early 2020s, the US policy community widely recognized that war games indicated a significant disadvantage for the US in a military conflict with China within the first island chain. While the US might initially have an advantage, it would incur immense costs thereafter, and there was even a high probability of failing to achieve military objectives. Some experts claimed the cost ratio for the US and China in a conflict within the first island chain would be as high as 10,000:1 (Allison 2020). Therefore, they proposed reducing US Forces Korea by more than half and retreating main US forces to the second island chain, such as Guam or Australia, to preserve strength, with allies like South Korea responsible for forward defense (Kavanagh and Caldwell 2025).

However, not only Colby but also Admiral Samuel Paparo, Commander of the US Indo-Pacific Command, expressed concern that if US forces withdraw from the first island chain, the incentive for regional US allies to contain the overwhelmingly capable China would drastically diminish, leading to the collapse of the alliance network. Colby had long emphasized the need for the US to provide incentives for allies to participate in an "Anti-hegemonic Coalition" without getting directly entangled in attrition warfare (Colby 2021), and Admiral Paparo proposed a strategy to maintain deterrence against China within the first island chain through long-range strike capabilities—such as unmanned systems, Typhon missiles, Naval Strike Missile (NMESIS), and B-21 stealth bombers—from outside China's A2/AD defense envelope (Paparo 2025).

Therefore, it is evident that during 2025, discussions between the Caldwell camp and the Colby camp competed regarding the direction of the new US defense strategy. The former advocates for 'Offshore Balancing,' which involves retreating US military power to the second island chain (where Guam and Australia are located) and shifting the responsibility for defense of the first island chain to allies. This perspective emphasizes reducing unnecessary overseas interventions and focusing on 'homeland defense.' The latter, while acknowledging the importance of homeland defense, maintains that the Indo-Pacific region, crucial for future growth engines, remains important, and sufficient capabilities must be provided to allies to prevent China from emerging as the hegemon in this region. Those holding this view prioritize maintaining sufficient deterrence against China and managing the alliance network in the Indo-Pacific.

(2) Caldwell vs. Colby: NSS vs. NDS?

The NSS should be read in the context of these debates within the US defense policy community. In his foreword, Trump alludes to the priorities of national interest by mentioning his key achievements since taking office: (1) restoring America's borders, (2) removing radical gender ideology and "woke madness" from the military, (3) strengthening the military through investments totaling $1 trillion, (4) rebuilding alliances and increasing allies' contributions to collective defense, (5) restoring energy production and self-sufficiency, and (6) reshoring key industries.

The National Security Priorities outlined in the main body of the document directly reflect Trump's perceptions. However, the list—comprising (1) ending the era of mass migration and border security, (2) protecting fundamental rights and freedoms (e.g., combating "political correctness" and "woke culture"), (3) burden-sharing and burden-shifting with allies, (4) realigning efforts through peace (e.g., resolving peripheral conflicts like Cambodia-Thailand, Kosovo-Serbia), and (5) economic security (e.g., balanced trade, securing supply chains, re-industrialization, energy dominance)—does not mention China even once.

While domestic media focused solely on the absence of North Korea in the NSS, what is more intriguing is the US perception of China. Throughout the document, China is mentioned 21 times. However, in this document outlining the broad strokes of US national security strategy, China is never referred to as an object of "military deterrence." Even the section discussing strategy for the Asian region is titled "Win the Economic Future, Prevent Military Confrontation." This section criticizes the previous Democratic administration's flawed perspective on China (e.g., the expectation that an economically growing China would integrate into the "rules-based international order") and emphasizes the need to compete and win against China in areas such as artificial intelligence (AI), quantum computing, autonomous systems, and energy, but it does not include any language about militarily pressuring China. The subsequent section, which categorizes military threats, mentions the Taiwan issue and explains its importance in relation to "semiconductor production" and the value of the South China Sea, through which approximately one-third of global maritime trade passes annually. South Korea is mentioned only three times, referred to as a country with "net foreign assets" or one that needs to "increase defense cost-sharing" (Whitehouse 2025).

Therefore, the NSS appears to lean more towards the Caldwell perspective than Colby's. The omission of "military pressure and containment of China" and "response to North Korean threats" is likely not a mere oversight but a more sensitive reflection of President Trump's core interests: prioritizing economy, avoiding confrontation, and pressuring allies on costs. It is possible, however, that the content regarding military containment of China has been reserved for the NDS, which is expected to be released soon.

(3) Outlook for the 2026 National Defense Strategy (NDS): Maintaining Overwhelming Military Power Amidst the End of the Unipolar Era

To accurately grasp the direction of US defense strategy, the content of the NDS may be more crucial than the NSS. To anticipate the yet-to-be-released NDS, it is essential to closely examine the speeches of Secretary of Defense Hegseth. Comparing his Shangri-La Dialogue speech on May 31, 2025, delivered before the NSS release, with his speech at the Ronald Reagan Presidential Library on December 6, shortly after the NSS release, is particularly important.

In his Shangri-La Dialogue speech, Hegseth identified three core objectives for the US military: restoring warrior ethos, rebuilding the force, and reestablishing deterrence. While he first mentioned homeland defense and the "Golden Dome" as priorities for deterrence, he subsequently devoted a significant portion to explaining deterrence against China. Presenting evidence of China's pursuit of hegemony, he stated, "It is public information that Xi Jinping has ordered the military to be ready to invade Taiwan by 2027." He then outlined the Department of Defense's top priority as implementing "deterrence by denial" along the first and second island chains through "forward-postured, combat credible forces" and indicated directions for security cooperation with the Philippines to achieve this. He also mentioned weapon systems like NMESIS, proposed by Admiral Paparo, and enhancing interoperability with allies' advanced technology weapon platforms (Hegseth 2025a). Overall, the speech aligned well with the grand strategy envisioned by Colby.

However, the tone shifts in the December speech. From the outset, he references the Weinberger Doctrine, named after former Secretary of Defense Caspar Weinberger during the Reagan administration, and introduces its tenets. The core principle is to deploy forces only when vital national interests of the US or its allies are at stake, to intervene militarily only when capable of achieving clear objectives, and to consider military deployment solely as a last resort. This emphasizes a logic of restraint, advocating for cautious use of military force.

He then lists the military's "four core efforts": (1) Defense of the US homeland and Western Hemisphere (e.g., deploying forces to secure borders, combat drug cartels, establish the "Golden Dome," and maintain US military superiority in the Western Hemisphere); (2) Deterring China through strength, not confrontation (e.g., maintaining a "balance of power" rather than "domination" over China, implementing "deterrence by denial" along the first island chain, and preserving overwhelming military superiority); (3) Increasing burden-sharing by allies and partners (e.g., setting a target of 5% of GDP for defense spending); and (4) Securing a decisive advantage in the US defense industrial base (e.g., transitioning to a dynamic vendor-centric system to increase the speed and scale of weapons production) (Hegseth 2025b).

While seemingly not significantly different from the May speech, there are clear shifts in emphasis. First, in May, domestic and overseas security priorities were mentioned together, presented as simultaneous objectives without a hierarchy between homeland defense and deterring China. In contrast, the December speech clearly established deterrence against China as the second priority. Second, the May speech explained the main lines of effort for US defense capabilities in the context of deterring China, whereas the December speech frames most discussions on military strengthening, including missile and cyber defense and the modernization of the nuclear triad, within the context of homeland defense. Third, and most notably, it explicitly declares that "the unipolar moment is over" yet maintains the objective of ensuring US military power in the Indo-Pacific is "so strong that aggression is not even considered."

This suggests that the NDS, when eventually released, is unlikely to fully converge with the Caldwell viewpoint but will likely present a form closer to the NSS. Specifically, the core principles expected to permeate the NDS are the need for selectivity and focus, given that the US no longer possesses the capacity for global hegemony, and the aim to achieve "peace through strength" by ensuring US military power in the Indo-Pacific is overwhelmingly superior to China's. Although these principles may appear contradictory at first glance, their intent can be inferred by focusing on keywords such as "focus," "prioritization," and "clarity of purpose." In essence, the core of US defense policy will involve the deployment of military force for border control and drug interdiction, and the maintenance and use of overwhelming capabilities in the Western Hemisphere. Simultaneously, in the Indo-Pacific, the strategy will involve countering China's conventional military superiority within the first island chain through A2/AD and acquiring the necessary capabilities for this.

For example, consider Admiral Paparo's "Hellscape" concept, presented in an interview with The Washington Post. The idea is to immediately deploy thousands of unmanned submarines, unmanned surface vessels, and aerial drones into the Taiwan Strait if China attempts an invasion of Taiwan, thereby transforming the area into an "unmanned hellscape." This strategy aims to prevent China from executing a "fait accompli" strategy of swift conquest of Taiwan, while forcing China to incur massive losses and minimizing US casualties (Washington Post 2024). In addition, the US will present plans to focus on homeland defense while maintaining overwhelming military power against China, likely through active utilization of allies, as will be discussed later.

3. Changes in China's Defense Strategy: From 'Strategic Substitution' to Nuclear Great Power Competition

Behind Hegseth's formalization of the "end of the unipolar era" lies the dramatic growth of China's military power. Particularly within the first island chain in the Western Pacific, China's conventional forces and informationized weapon systems (including precision strike, cyber, and anti-space weapons) are already assessed to have eroded the US's exclusive dominance. China, with a defense budget exceeding 50% of the US defense budget based on Purchasing Power Parity (PPP) (Robertson 2025), is concentrating its vast financial resources on building military capabilities within the first island chain. Furthermore, the recent pace of China's vertical nuclear proliferation suggests that China will achieve a significant degree of "Strategic Autonomy" in its competition with the US in the short to medium term.

(1) The Third Taiwan Strait Crisis (1995-1996) and the Emergence of the 'Strategic Substitution' Posture

A key to understanding the buildup of China's military power within the first island chain is the concept of "Strategic Substitution" proposed by Fiona S. Cunningham (Cunningham 2025). There has been extensive theoretical and policy discussion on how a nuclear-armed state can achieve its political objectives in a limited conflict with another nuclear-armed state without resorting to full-scale war, as exemplified by the India-Pakistan military confrontation in April-May of last year.

The core issue, as presented in Snyder's "Stability-Instability Paradox" (Snyder 1965), is whether victory in conflict can be achieved using only conventional forces without crossing the nuclear threshold. If one has a conventional advantage, a posture of "calibrated escalation" based on Robert Powell's concept of "limited retaliation" can be adopted. Conversely, if conventional forces are inferior to the adversary, a posture of "nuclear brinkmanship" based on Thomas Schelling's concept of "threat that leaves something to chance" is possible (Kim 2023).

However, Cunningham analyzes that China has chosen a "third way," distinct from both "brinkmanship" and "calibrated escalation." The catalyst for this was the Third Taiwan Strait Crisis in 1995-96. At that time, faced with two US carrier strike groups rapidly deployed by the Clinton administration, China experienced the humiliation of a "Leverage Deficit" due to a complete lack of response capabilities. Following the crisis, China did not engage in an arms race to emulate high-cost platforms like aircraft carriers, nor did it pursue brinkmanship by abandoning its "No First Use" nuclear policy.

Instead, China opted to build asymmetric capabilities by combining "Information-Age Weapons." This is precisely "strategic substitution." China focused on developing anti-ship ballistic missiles (ASBMs) like the DF-21D/DF-26, dubbed "carrier killers," anti-satellite weapons (ASATs) to disable US reconnaissance satellites and command and control (C4ISR) networks, and offensive cyber capabilities targeting power grids and command and control systems (NC3). As a result, China succeeded in creating a robust A2/AD environment within the first island chain. This signifies that even though the US maintains overall military superiority globally, it cannot guarantee victory in specific theaters like the Taiwan Strait or the South China Sea, thus achieving "deterrence by denial." Indeed, a 2019 US Department of Defense war game, which simulated 18 conflict scenarios within the first island chain, resulted in US defeat in all 18 instances, sending shockwaves through the US policy community (Kristof 2019).

(2) Vertical Nuclear Proliferation: The End of 'Minimum Deterrence' and the Pursuit of Mutual Assured Destruction (MAD)

Cunningham's explanation is insightful, but it overlooks one crucial change: China is currently undergoing a phase of rapid vertical nuclear proliferation, significantly increasing its number of nuclear warheads (Figure 1). While the previous "strategic substitution" strategy had a defensive nature, countering the conventional force disadvantage against the US by developing "asymmetric information weapons" instead of pursuing brinkmanship, the rapid augmentation of nuclear capabilities, which concerns the US Department of Defense, signifies a fundamental shift in China's security strategy. Why is China accelerating its nuclear capability enhancement beyond its successful strategic substitution strategy?

[Figure 1] Estimated Chinese Nuclear Warhead Graph (Based on SIPRI Data, Created by Gemini 3.0)

The most crucial driver lies in establishing strategic stability through a 'Mutual Assured Destruction (MAD)' relationship with the United States. Military innovation driven by 21st-century advanced technology, particularly innovations in 'precision' and 'transparency,' has ushered in 'the new era of counterforce' (Lieber and Press 2017), and the military application of AI is further accelerating this transformation (Kim Yang-gyu 2024). Consequently, the existing approximately 200 nuclear weapons are insufficient even to implement a Minimum Deterrence strategy. As of 2025, China possesses 600 operational nuclear warheads, with projections indicating over 1,000 warheads by 2030. This represents a steep growth trajectory compared to China's nuclear arsenal, which remained around 200 warheads until 2020 (SIPRI 2025; DoD 2025). This is clearly indicative of an attempt to secure second-strike capability through redundancy in nuclear warheads.

Qualitative growth is also proceeding at a formidable pace. Until 2022, in terms of the nuclear triad, China lagged significantly behind the United States in all areas except missile forces (Wu 2021/2022). However, it is now believed to be equipped with over 100 solid-fuel Intercontinental Ballistic Missile (ICBM) silos loaded with DF-31 class ICBMs, maintaining an 'Early Warning Counterstrike (EWCS)' posture. Furthermore, it appears to be operating the new Submarine-Launched Ballistic Missile (SLBM), the JL-3, with an estimated range of 10,000 km, aboard six Jin-class (Type 094) strategic nuclear submarines (SSBNs). Additionally, following the H-6N bomber with aerial refueling capabilities, China is developing the H-20 stealth bomber (DoD 2025).

This enhancement of nuclear capabilities creates a lethal synergy when combined with the aforementioned 'informationized weapons.' In particular, the operational deployment of the DF-26 missile, which can rapidly switch between nuclear and conventional warheads, creates an 'entanglement' dilemma. In a localized conflict scenario, if the U.S. military attempts to strike Chinese conventional missiles, China might misinterpret this as a nuclear attack and, under the fear of 'use-it-or-lose-it,' press the nuclear button. This drastically increases the risk of a conventional conflict between the U.S. and China escalating into an accidental nuclear war. Paradoxically, this fear may also act as a deterrent to U.S. intervention. If China maintains its current trajectory and possesses a credible second-strike capability against the United States, establishing a firm MAD between the two nations, dynamics that make it difficult to 'sacrifice New York to save Paris' will come into play, leading to a sharp decline in the credibility of the U.S. nuclear umbrella provided to its allies within the operational theater. This could become a potent factor in creating fissures within the robust U.S. alliance network.

(3) China's '2025 Defense White Paper': Pursuing Superiority within the First Island Chain and Long-Term U.S.-China Military Balance

What is the security landscape in Northeast Asia that China envisions in the medium to long term through its rapid military buildup? The answer can be found in its three-stage military modernization roadmap aimed at achieving the ultimate goal of the 'great rejuvenation of the Chinese nation' by 2049. By 2027, the centenary of the People's Liberation Army, China aims to complete the integration of mechanization, informationization, and intelligentization, thereby acquiring the capability to win 'strategically decisive victories' by deterring U.S. intervention in conflicts within the First Island Chain, particularly in the event of a Taiwan contingency. This is not merely about securing defensive capabilities but about achieving 'Strategic Counterbalance' against the United States in the Western Pacific, making military intervention by the U.S. difficult. By 2035, China aims to have fundamentally completed the modernization of its national defense and military, and by 2049, it seeks to build 'world-class forces' capable of global operations on par with the U.S. military, thereby solidifying its hegemonic position (DoD 2025).

2026 is part of that process. The white paper 'China's National Security in the New Era (新时代的中国 国家安全),' released in May 2025, centers on the 'holistic approach to national security (总体国家安全观)' (State Council Information Office 2025). This concept expands the notion of security beyond the military to encompass over 20 domains, including politics, economy, culture, society, and technology. Notably, it emphasizes the 'virtuous cycle of high-quality development and high-level security (必须推动高质量发展和高水平安全良性互动),' under which U.S. trade controls and supply chain decoupling attempts against China are framed not merely as economic issues but as 'security problems threatening the survival of the system.' Self-reliance in food, energy, and core technologies becomes a prerequisite for strengthening national defense, and conversely, a strong military serves as a shield protecting China's 'Right to Development' from external coercion.

Second, China also demonstrates a tendency to prioritize its core interests. While defining core interests as 'regime security, sovereignty, territorial integrity, the welfare of the people, and sustainable economic and social development (国家政权、主权、统一和领土完整、 人民福祉、经济社会可持续发展),' it clearly articulates the principle that 'political security must be prioritized (坚持把政治安全摆在 首位).' In this context, political security refers to the safeguarding of 'the leadership position of the Communist Party of China' and 'the socialist system.' Taiwan is thus elevated to an 'inalienable core interest.' Defense Minister Dong Jun emphasized at the 2024 Shangri-La Dialogue that 'The Taiwan question is at the core of China’s core interests' (Dong 2024). For China, the unification of Taiwan is not merely a territorial recovery but a litmus test for the legitimacy of the Communist Party's rule (political security). Therefore, while advocating for 'peaceful unification' as its priority, China explicitly reserves the right to use force and signals its intent to counter any U.S. attempts to prevent unification as a 'threat to its system,' employing all means, including nuclear deterrence.

Finally, China is competing with the United States not only in hard power but also in norm competition. President Xi Jinping's proposed 'Global Security Initiative (GSI)' criticizes the U.S.-led alliance system as 'Cold War mentality' and 'exclusive multilateralism.' It advocates for conflict resolution through dialogue and cooperation based on opposition to the pursuit of 'absolute security' and the concept of 'common security,' thereby presenting an alternative to the U.S.-led alliance system (Dong 2024). This aims to rally Global South countries seeking neutrality in the U.S.-China competition. It represents a long-term strategy to break through the U.S. containment and establish a new security governance and partnership network centered around China.

In conclusion, the future beyond 2026, as indicated by China's defense white papers and strategic documents, is clear. China appears to have concluded that it must complete the foundation for Taiwan's unification to maintain the Communist Party's regime, and to this end, it must militarily overwhelm the United States at least within the First Island Chain. Economic strength is the nourishment for military power, and military power is the safety net that guarantees economic development. As this robust 'development-security complex' clashes with the U.S. concept of 'peace through strength,' the waves of U.S.-China strategic competition in the Western Pacific are bound to rise further.

4. Medium- to Long-Term Northeast Asian Military Order Outlook: The Confrontation of 'Spear and Shield' within the First Island Chain

Amidst the shifting defense strategies of the U.S. and China, how will the medium- to short-term military order in Northeast Asia evolve? While the upcoming National Defense Strategy (NDS) is expected to acknowledge that 'the unipolar era is over,' it will likely still present 'peace through overwhelming U.S. strength' as its vision. This provides a crucial clue for predicting the U.S.-China military balance beyond 2026. Let us examine this from the perspectives of nuclear competition, non-nuclear competition within the First Island Chain, and the utilization of alliance networks.

First, at the foundational level of nuclear competition, it is important to note that China remains at a distinct disadvantage compared to the United States. Although China's vertical nuclear proliferation is accelerating, its current arsenal of approximately 600 nuclear weapons is insufficient to reach the level of MAD established between the U.S. and the Soviet Union during the Cold War. In the era of precision and transparency military revolutions, a far greater number of nuclear warheads is required to establish MAD than in the past. Therefore, China will likely position its nuclear capabilities as a 'last resort' and a shield against U.S. nuclear coercion, while maintaining a 'strategic alternative' posture, as described by Cunningham, at the core of its actual military strategy. In other words, rather than a full-scale nuclear war, China's defense strategy will likely center on an asymmetric denial strategy that increases the cost of U.S. military intervention within the First Island Chain by utilizing precision-guided missiles, cyber, and space weapons.

Therefore, the core of the U.S.-China military competition will ultimately be a clash of non-nuclear forces within the First Island Chain, a battle between China's 'anti-access/area denial (A2/AD)' capabilities (shield) and the U.S.'s power projection/breakout capabilities (spear). It is noteworthy that information-age weapons and asymmetric strategies are not exclusive to China. In the competition for advanced weaponry, the United States still holds an advantage over China. As seen in the concept of a 'drone hellscape,' the U.S. can respond asymmetrically, using methods similar to those employed by China, to penetrate China's A2/AD shield. This concept of inundating the Taiwan Strait with thousands of unmanned weapon systems to strike Chinese landing fleets, aiming to 'make their lives utterly miserable for a month,' is essentially the U.S. version of an 'anti-access' strategy. In this context, the key, as emphasized by both the NSS and Hegseth, lies in a robust industrial base, i.e., manufacturing competitiveness, capable of supporting mass production. The Western Pacific beyond 2026 will thus become a chaotic zone of stalemate where the U.S. and China mutually deny each other's power projection, a mix of spears and shields, with the decisive factor being the production capacity of advanced technology weapons.

One additional important issue to consider is the security partnership network. In fact, the most significant reason the U.S. can be confident of its overwhelming superiority even after the end of the unipolar era is not its overwhelming 'technological hegemony' but its 'alliance network.' The 'Burden Sharing' emphasized by the Trump administration goes beyond a mere demand for allies to contribute more financially to security; it is evolving into 'Capability Sharing.' The approval for South Korea to construct nuclear-powered submarines (SSNs) during the ROK-U.S. summit in Gyeongju last November, and the deployment of the Typhon missile system and the NMESIS mobile precision strike missile system to the Philippines (Lim Hwa-seop 2025/05/12), clearly illustrate U.S. intentions. The U.S. is pursuing a strategy of strengthening allied capabilities and enhancing interoperability to encircle China with allied assets and form a forward defense line. The efforts to build a 'lattice security network' that tightly connects multilateral consultative bodies like S-Quad are a prime example (Park Jae-jeok 2026).

This concept, where 'enhancing allies' security capabilities' directly translates to 'increasing U.S. deterrence against China,' is a particularly painful point for China. China must contend not only with U.S. forces but also with the precision strike missile and air/naval capabilities of South Korea, Japan, and the Philippines, which can conduct joint operations with the U.S. military. Therefore, from a military perspective, a crucial task for China in securing regional hegemony is to dismantle the U.S. alliance network, and to this end, China will increasingly focus on coercion and wedge strategies. Strengthening ties with BRICS and the Global South, and proposing a 'Global Governance Initiative (GGI)' to establish alternative multilateral institutions, are part of these efforts (Lee Dong-ryul 2026).

5. South Korea's Defense Policy in 2026

Amidst the intensifying military competition between the U.S. and China within the First Island Chain, what preparations are necessary for South Korea's defense strategy in 2026? With the U.S. pursuing 'America First' based on 'flexible realism' in its national security strategy under a potential second Trump administration, and with China's Xi Jinping prioritizing domestic political interests based on core interests, it is evident that South Korea must also adopt a cool-headed, 'national interest-centric' approach.

The first issue to consider is South Korea's positioning within the process of modernizing the ROK-U.S. alliance. The approval for nuclear-powered submarines (SSNs) at the Gyeongju ROK-U.S. summit last November should not be viewed merely as a diplomatic triumph achieving a 30-year aspiration or a symbol of independent defense. Considering the direction of U.S. defense strategy changes, this represents a development that poses significant strategic dilemmas for South Korea. The U.S. demand for regular maintenance, repair, and overhaul (MRO) of U.S. naval vessels in South Korea implies that South Korean shipyards will become logistical bases for the U.S. Navy, and in the event of a military conflict between the U.S. and China within the First Island Chain, South Korea could become a primary target for Chinese strikes, whether it wishes to or not.

Therefore, South Korea needs to be vigilant against the 'modernization of the ROK-U.S. alliance' being solely utilized as a means to enhance U.S. deterrence capabilities in the Indo-Pacific region. In this context, the primary objective of strengthening the ROK military's capabilities, including SSNs, should be clearly defined and communicated externally as 'enhancing strategic stability on the Korean Peninsula,' rather than 'intervening in regional conflicts.' SSNs should be operated not for containment of China but to enhance South Korea's role and responsibility in deterring North Korea by constantly tracking and monitoring North Korean SLBM-carrying submarines. South Korea should consider ways to contribute to the development of the ROK-U.S. alliance by avoiding the 'threat of entanglement' while reducing the U.S. security burden.

Second, efforts to leverage the wartime operational control (OPCON) transfer as strategic leverage are also necessary. South Korea playing a leading role in the defense of the Korean Peninsula aligns perfectly with the defense policy direction of a potential second Trump administration, making it a welcome agenda item for the U.S. Indeed, at the 57th ROK-U.S. Security Consultative Meeting (SCM) last November, the defense ministers of both countries agreed to pursue verification of the Full Operational Capability (FOC) of the Future Combined Forces Command headquarters within the year, thereby completing Phase 2 of the Conditions-based OPCON Transition Plan and moving into the final Phase 3 Full Mission Capability (FMC) assessment (Kim Ho-jun, Lee Jeong-hyun, Kim Cheol-seon 2025/11/14). The U.S. now desires allies that can take responsibility for their own security and possess substantial capabilities for the benefit of U.S. interests. OPCON transfer is no longer a matter of principle for 'independent defense' but an unavoidable reality.

Therefore, South Korea must leverage the acceleration of OPCON transfer to enhance its actual capabilities and bolster its deterrence against North Korea. It is necessary to secure maximum support from the U.S. while building core capabilities currently lacking in the ROK military, such as Intelligence, Surveillance, and Reconnaissance (ISR) assets, missile defense systems, space and cyber capabilities, and the military application of AI. This presents an opportunity for a 'quantum leap' in South Korea's security capabilities that aligns with the U.S.'s new defense strategy while also benefiting South Korea.

Third, South Korea must establish a Korean-style 'strategic alternative' posture to counter the structural pressures of the demographic cliff and the deepening North Korea-Russia alignment. The escalating military cooperation between North Korea and Russia, coupled with North Korea's continued nuclear capability advancements, clearly poses an existential threat to South Korea. While currently reliant on the U.S. nuclear umbrella, self-reliant efforts must be expanded, and in this regard, the 'strategic alternative' posture based on information-age weapons, which China has successfully implemented, should be actively considered. Furthermore, in light of the threat of troop reduction due to the demographic cliff, the early operationalization of AI-based manned-unmanned combined combat systems is a goal that must be achieved. This is also an essential condition for the ROK military to possess independent operational capabilities after the OPCON transfer. While ensuring interoperability in conjunction with the U.S.'s AI-based defense reforms, efforts must be made to secure independent algorithms and data sovereignty optimized for South Korea's terrain and battlefield environment. Amidst the intensifying U.S.-China strategic competition, South Korea must seize 2026 as an opportunity for an innovative leap in defense capabilities. ■

References

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■ Kim Yang-gyu_Professor, National Defense University Graduate School of Security Studies.

■ Editor: Lee Sang-jun_EAI Research Fellow

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