[Global NK Commentary] US-China Maritime Power Transition, the First Island Chain, and the Korean Peninsula

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I. The Trump Administration's Second Term Maritime Action Plan (MAP)

In April, the Trump administration's second term announced an executive order titled "Restoring America's Maritime Dominance." This order encompasses all available policy tools to reorganize the shipbuilding supply chain and offset the US's disadvantage in shipbuilding capacity. The fundamental objectives of this executive order include securing stable federal funding for shipbuilding, enhancing the international competitiveness of merchant vessels manufactured in or operated under the US flag, rebuilding the maritime industrial base, and strengthening employment, training, and retention programs for the shipbuilding workforce. Specifically, the National Security Advisor is required to submit a Maritime Action Plan (MAP) to the President within seven months, in consultation with the Secretaries of State, Defense, Commerce, Labor, Transportation, the USTR, and the Secretary of Homeland Security. This plan notably includes measures to promote investment in supply chains essential to the US maritime industrial base, while simultaneously investigating unfair practices by China's shipbuilding sector and imposing tariffs if necessary.

Additionally, the executive order includes provisions for establishing Maritime Prosperity Zones to attract allied and domestic private investment in the US maritime industry, and creating a Maritime Security Trust Fund to stably support the Maritime Action Plan (MAP). Most importantly, the Maritime Action Plan proposes investments and reforms in the overall training and education of the maritime industrial workforce to overcome the chronic delays in naval vessel construction and the reduction and retirement of the shipbuilding industry workforce, issues that have been pointed out annually by the Congressional Budget Office through its shipbuilding budget and execution analysis. The plan also mentions measures to increase the number of US-flagged merchant vessels operating internationally, which is considered a measure to compensate for a potential shortage of vessels in times of crisis by securing a larger pool of civilian ships that can be requisitioned for military use. In a similar vein, the Secretary of Defense is required to conduct an audit of the Ready Reserve Fleet within three months and submit guidelines for the maintenance, support, mobilization, and financial backing of a strong Ready Reserve Fleet.

II. 21st Century US-China Maritime Power Transition

The Trump administration's second term Maritime Action Plan is a reflection of the United States entering a phase of relative hegemonic decline. Although China's GDP has stagnated from $17 trillion to $18 trillion between 2021 and 2024, while the US GDP has increased from $24 trillion to $29 trillion during the same period, thus moderating the pace of China's overtaking in terms of economic size, the structural shift of power transition between the US and China continues. The Trump administrations (first and second terms) and the Biden administration, to varying degrees, have sought to continuously respond to the US-China power transition through policies of global supply chain restructuring, represented by tariff policies and de-risking. During its term, the Biden administration did not recognize the WTO's 2022 arbitration ruling that the steel and aluminum tariffs imposed during the Trump administration's first term in 2018 violated trade norms. On May 30, 2025, President Trump announced he would increase tariffs on steel and aluminum from 25% to 50%. The policy of restructuring global supply chains, which began in earnest under the Biden administration, is expected to be at least maintained or further intensified under the Trump administration's second term.

Despite differences in strategic approaches based on political orientation, there is a certain consistency in the China policies pursued by the Biden administration and the Trump administrations (first and second terms), which is not unrelated to the continuation of the structural shift of the US-China power transition. As revealed in various international relations theories such as hegemony stability theory, power transition theory, and long cycle theory proposed by Charles Kindleberger, Robert Gilpin, A.F.K. Organski, and George Modelski, indicators for tracking the patterns of power transition include military power, economic power, financial power, industrial production capacity, technological capability, knowledge production capacity, and norm diffusion power. Among these, the most prominent power transition occurring between the United States and China today is the maritime power transition. While maritime power transitions occurred relatively frequently between Portugal, Spain, the Netherlands, Britain, and France in the 17th and 18th centuries, the 19th century saw naval competition between Britain, France, Germany, the United States, and Japan, with actual instances approaching maritime power transition being limited to the early 1860s between Britain and France, and between Britain and the United States in the 1910s and 1930s.

Considering Britain's decision in 1904 to politically accommodate the rising power of the United States in order to focus on the threat from Germany in continental Europe after the Venezuelan Crisis of the late 19th century, the maritime power transition between Britain and France in the early 1860s might be the only maritime power transition in the conventional sense throughout the 19th and 20th centuries. The case of Britain and Germany in the early 20th century, which is always cited as a classic example, did not involve German naval power surpassing British naval power. Although Japan significantly narrowed the gap in naval power with the United States by 1941 through highly concentrated domestic resource extraction capabilities, the Roosevelt administration and the US Congress enacted the Vinson-Trammel Act of 1934, the Second Vinson Act of 1938, and the Two-Ocean Navy Act of 1940, preventing Japan from surpassing US naval power in the Asia-Pacific theater.

In fact, in response to China's naval modernization, which began in earnest in 2012, the US Congress has consistently allocated more funds than requested by the President since 2015. The administration has also continuously increased its budget requests for warship construction from approximately $15 billion in 2015 to $30 billion in 2025, over a decade. The problem is that China, which leads the global shipbuilding market along with South Korea and has set naval modernization as a strategic goal, has been able to produce more warships during the same period. According to an analysis by the Center for Strategic and International Studies (CSIS) in March 2025, China and South Korea hold 53.3% and 29.1% of the global shipbuilding market share, respectively, while the US shipbuilding market share is a mere 0.1%. In terms of the number of warships, China's quantitative naval superiority occurred between 2015 and 2020. According to the US Department of Defense's 2024 report on China's military power, the Chinese Navy is currently the world's largest navy, possessing a total of 370 warships, and is expected to possess 395 and 435 warships in 2025 and 2030, respectively. In contrast, as of December 1, 2024, the United States possesses approximately 296 warships, and according to the budget proposal submitted in 2025, it is projected to have 294 warships by the end of fiscal year 2030.

III. Asymmetric Shipbuilding Capacity and the Trend of Maritime Power Transition in the United States

In the early 2000s, a prominent question in international relations scholarship was why a balance against the United States, which possessed unprecedented military power, did not emerge. According to traditional balance of power theory, it was expected that other great powers or states would form a coalition to balance against a superpower with overwhelmingly concentrated military power. However, this phenomenon did not occur after the end of the Cold War. One answer proposed was that the US is a maritime hegemon, and states do not feel a direct territorial threat from a maritime hegemon as they might from a continental hegemon, thus preventing the formation of a balance. While this argument is significant for highlighting the geographical and geopolitical context of security competition and threat perception, it has a flaw. The economic, financial, and shipbuilding capacities required to engage in a naval competition with a maritime hegemon, which incurs enormous costs in the 21st century, are inherently very limited for most great powers or states.

The fact that maritime power transitions were significantly less frequent in the 19th and 20th centuries compared to the 17th and 18th centuries, due to the higher threshold for naval competition in the industrial age, may attest to the importance of economic and shipbuilding capabilities. In the 19th century, France and Russia attempted naval competition against Britain, but apart from France in the early 1860s, no maritime power transition occurred. In the 20th century, Germany, Japan, Russia, and the Soviet Union can be seen as having engaged in naval competition within limits that did not lead to maritime power transition against Britain and the United States. However, 21st-century China has already acquired the economic and financial capacity and considerable shipbuilding capabilities to engage in naval competition with the maritime hegemon, the United States, despite qualitative disadvantages. In such cases, it becomes less important whether other countries intend to form an alliance against the United States. The balance against the United States has already occurred solely due to China's naval modernization.

Of course, the number of warships cannot be considered the sole or absolute criterion for evaluating naval power. Looking at the composition of fleets, the US Navy has many large warships such as cruisers and destroyers, while the Chinese Navy has more smaller warships like frigates and corvettes. The US operates 11 aircraft carriers, while China has 3 aircraft carriers and is building a fourth. In terms of displacement, the total displacement of the Chinese Navy is 1,854,000 tons, which is less than half of the total displacement of the US Navy, exceeding 4 million tons. In the case of submarines, all US Navy submarines are nuclear-powered, whereas most of the 55 Chinese submarines are diesel-powered, making them easier to detect, and only about 10 are nuclear-powered. While the US Navy still holds a qualitative advantage, the number of warships has historically been an important factor in the outcome of naval battles. More importantly, given the asymmetric disadvantage in the US shipbuilding capacity, the change in the number of warships cannot be overlooked.

According to the US Navy's shipbuilding plan submitted for 2025, the number of warships capable of launching missiles and torpedoes is projected to decrease in the short term over the next five to ten years, with a goal to rebound in firepower, represented by missile and torpedo launch capabilities, and fleet size starting in the 2030s. Current shipbuilding reflects past budget plans, so the trend of US-China maritime power transition, at least in quantitative terms, will intensify from 2025 to 2030. In the long term, the US Navy's 2025 shipbuilding plan aims to possess a total of 381 warships and 134 unmanned combat and underwater vehicles by the end of the 2030s. If this plan is realized, the size of the US Navy's fleet could increase to 390 by 2054. However, it remains uncertain whether US shipbuilding capacity and federal finances can realistically support this plan over the next 30 years. The Trump administration's second term recognizes the quantitative maritime power transition and the shipbuilding capacity disadvantage facing the United States and issued an executive order on April 9, 2025, to directly address these issues.

IV. The US First Island Chain Defense and the Korean Peninsula Amidst Maritime Power Transition

As mentioned, the Trump administration's second term Maritime Action Plan (MAP) was announced in early April, and specific plans for each item are to be submitted within three to seven months. Therefore, it is difficult to assess at this point how effectively the MAP will be implemented. However, it is clear that a quantitative US-China maritime power transition is virtually scheduled from 2025 to 2030, and depending on the unfolding situation, the US may continue to need efforts to offset its disadvantage in the number of warships even into the 2050s. The Trump administration's April executive order and the Maritime Action Plan demonstrate that the US at least clearly recognizes these problems and is making efforts to resolve them. Historically, maritime hegemons have shown efforts to readjust or strengthen their primary maritime defense lines in response to significant maritime power transitions or major shifts in naval military balance due to the formation or dissolution of alliances. In the 1860s, Prime Minister Palmerston strengthened Britain's coastal defense, and in the 1890s, Prime Minister Salisbury readjusted Britain's primary maritime defense line in the Mediterranean in response to the combined naval power of the Franco-Russian alliance.

From the latter half of the 1930s to the early 1940s, President Roosevelt defined the primary maritime defense line in the Asia-Pacific theater. In January 1939, he shared his vision for the US primary maritime defense lines in both the European and Asia-Pacific theaters with members of the Senate Military Affairs Committee. In this context, how the United States envisions its primary maritime defense line in the Indo-Pacific region from 2025 to 2050 is a matter directly related to stable crisis management and peace in the Indo-Pacific region. Considering the significant changes brought about by the current US-China maritime power transition and the US conception of its primary maritime defense line, it becomes understandable that the issue concerning Taiwan cannot be confined solely to cross-strait relations. For South Korea, which possesses a modernized navy and world-class shipbuilding capabilities, albeit not on the same scale as Japan, this situation on one hand amplifies anxieties about maritime conflict, but on the other hand, it presents a significant opportunity to maximize South Korea's strategic value.

Recent remarks by the Commander of the US Forces Korea, who likened the Korean Peninsula to an aircraft carrier, and the leaked discussions about the strategic flexibility of US Forces Korea, although officially denied by government officials due to political implications, should be coolly understood as matters related to the ongoing US-China maritime power transition and the readjustment of the US primary maritime defense line. It is imperative to consider what contributions South Korea can make to consolidate peace and stability in the Indo-Pacific region based on a clear understanding of reality and to make wise policy choices. On the other hand, North Korea has recently been making efforts in naval modernization linked to its nuclear capabilities, exposing its latest destroyer and a strategic nuclear submarine as a means of nuclear delivery.

Specifically, North Korea launched the new destroyer Choe Hyon-ham in April, which was recently reported again through satellite imagery related to salvage operations, thereby modernizing its conventional naval forces. Simultaneously, in terms of its nuclear force structure, it is expanding its maritime operational weapon systems to secure a second-strike capability. Notably, the Kim Gun Ok Hero submarine, unveiled in September 2023, is equipped with 10 vertical launch tubes, 4 large tubes for submarine-launched ballistic missiles (SLBMs), and 6 small tubes for cruise missiles (SLCMs). Kim Jong Un referred to it as a "tactical nuclear attack submarine." This is considered part of North Korea's long-term effort to build a nuclear force structure based on SLBMs rather than intercontinental ballistic missiles (ICBMs). In addition, in 2023, North Korea test-fired a strategic cruise missile (SLCM) from a new patrol vessel, the Amrok-class, under Kim Jong Un's observation. North Korea also tested new and improved strategic cruise missiles last year and this year, and conducted two tests of a nuclear torpedo launch using an unmanned underwater vehicle in January 2024.

South Korea faces the challenge of simultaneously responding to the ongoing US-China maritime power transition and North Korea's naval modernization and naval nuclear armament, both in the short term by 2030 and in the long term by 2050. While concerns about the widening naval power gap with China have been consistently raised in the US over the past few years, the Trump administration's second term Maritime Action Plan indicates that the time has come for the US to respond by adjusting its grand strategy. From this year until 2030, and extending to 2050, South Korea needs to understand the strategic considerations of the United States and proactively design an initiative for US-ROK shipbuilding cooperation utilizing South Korea's shipbuilding capabilities. In relation to the readjustment of the US primary defense line, South Korea should specifically consider how it can contribute to deterrence aimed at regional stability and peace, and emphasize the necessity of deepened integrated extended deterrence between the US and South Korea as an advanced response to North Korea's naval nuclear armament. ■

■ Oh In-hwan_Senior Research Fellow, EAI

■ Contact and Editing:Kim Chae-rin, EAI Research Assistant

    Inquiries: 02 2277 1683 (ext. 208) | crkim@eai.or.kr