South Korea’s Nuclear-Powered Submarine Is a Strategic Alliance Investment
Some critics in the United States question whether South Korea truly needs nuclear-powered submarines, arguing that conventional submarines and unmanned systems may offer a more affordable and practical alternative. Any program with such a large price tag and technical complexity deserves rigorous scrutiny. But focusing too narrowly on cost and platform alternatives overlooks two overlapping challenges facing the United States: rapidly expanding undersea threats from China and North Korea, and an American shipbuilding and submarine industrial base under severe strain.
We are past the point of a theoretical debate. A 2025 U.S.-ROK joint fact sheet confirmed that the United States had approved South Korea’s construction of nuclear-powered attack submarines. The two countries also agreed to work closely on project requirements, including avenues for sourcing fuel. The same document identified investment in U.S. shipyards, workforce development, shipyard modernization, maintenance, repair and overhaul, and supply-chain resilience as areas for deeper bilateral cooperation.[1] Submarine development and shipbuilding investment are increasingly being discussed within the same strategic framework.
Consider the scale of the undersea challenge. The Pentagon’s 2024 assessment counted roughly 60 submarines in the Chinese navy: six nuclear-powered ballistic-missile submarines, six nuclear-powered attack submarines, and 48 diesel-powered or air-independent-propulsion attack submarines. It projected that China’s submarine force could grow to 80 boats by 2035.[2] North Korea, meanwhile, is openly pursuing more capable undersea forces. In late 2025, Pyongyang publicized what it described as an 8,700-ton strategic nuclear submarine project.[3] The maturity and eventual operational capability of that program remain uncertain, but North Korea’s intention to extend its nuclear and missile ambitions beneath the sea is difficult to ignore.
While potential adversaries expand their fleets, the U.S. undersea force and the industrial base that sustains it are under pressure. According to the Government Accountability Office, U.S. attack submarines accumulated 6,494 days of depot-maintenance delays between fiscal years 2016 and 2025. Without mitigation, 15 attack submarines could collectively accumulate more than 14,000 days of inactive idle time through fiscal year 2030. The GAO also estimated that, over the same decade, the Navy spent $4.2 billion crewing, maintaining, and supporting attack submarines that were either waiting to enter shipyards or delayed in completing maintenance.[4]
Against that backdrop, a South Korean nuclear-powered submarine should not be viewed as a competitor to American sea power. If South Korea can assume a greater share of persistent undersea surveillance and tracking missions around the Korean Peninsula and nearby waters, the United States could face less pressure to cover every regional requirement with its own scarce attack submarines. This would not replace the U.S. Navy. It would give U.S. commanders more options and greater operational flexibility. That is what meaningful alliance burden-sharing should look like.
Nor should the debate be framed as a rigid choice between nuclear-powered submarines and conventional boats or unmanned systems. South Korea will continue to need conventional submarines and unmanned platforms for missions in and around its littoral waters. But platforms optimized for coastal operations are not interchangeable with vessels designed for prolonged submerged missions, sustained high-speed maneuver, and persistent tracking. The real question is not which single platform should do everything, but what combination of capabilities the alliance needs in a changing undersea environment.
Yet the security benefits are only part of the equation. The economic and industrial case is just as important.
The White House’s 2026 Maritime Action Plan paints a stark picture. Less than 1 percent of new commercial ships are built in the United States. The plan identifies only 66 shipyards nationwide, including just eight active shipbuilding yards. It describes the status quo as creating significant security and supply-chain dependency problems and calls for greater investment, workforce development, shipyard modernization, and deeper cooperation with allies and partners.[5]
South Korea is already beginning to provide some of the capital and industrial capacity the United States needs. The 2025 U.S.-ROK joint fact sheet includes $150 billion in Korean investment in the shipbuilding sector approved by the United States.[1] This framework creates a pathway to channel Korean capital and world-class shipbuilding expertise into American shipyards, workers, and supply chains.
The benefits are already becoming tangible. Hanwha has announced a $5 billion infrastructure program for its Philadelphia shipyard, including two additional docks and three new quays, with the goal of increasing annual production from fewer than two vessels to as many as 20.[6] Pennsylvania officials say the broader expansion of the Philadelphia Navy Yard has the potential to support up to 5,000 jobs, including significant numbers of good-paying union jobs.[7] These are not vague promises about benefits that may someday flow overseas. They are concrete examples of Korean capital and shipbuilding expertise being used to expand American facilities and production capacity, with the potential to support thousands of American jobs.
A South Korean nuclear-powered submarine program will not, by itself, solve every weakness in the U.S. maritime industrial base. That is precisely why Washington should help shape the project rather than merely judge it from the sidelines. If submarine cooperation is linked to investment in American shipyards, joint supply chains, workforce training, and maintenance and repair cooperation, South Korea’s security requirements can reinforce America’s maritime industrial revival.
There is no denying that a South Korean nuclear-powered submarine program would be expensive. Budgets, timelines, operational requirements, and safeguards must be subject to rigorous oversight. But reducing the debate to cost alone would define American interests far too narrowly.
The United States stands to gain two strategic returns. First, a more capable ally able to assume a greater role in confronting Chinese and North Korean undersea threats would give the U.S. Navy greater operational flexibility. Second, the project can create opportunities to channel Korean capital and shipbuilding expertise into American shipyards, workers, jobs, and supply chains.
Washington should move beyond a narrow debate over whether South Korea needs nuclear-powered submarines at all. The more important question is how to structure the initiative so that it strengthens deterrence against North Korea and China while also rebuilding America’s maritime industrial base. Done right, this is one alliance investment that can generate two major strategic returns.
[Sources]
[1] The White House. “Joint Fact Sheet on President Donald J. Trump’s Meeting with President Lee Jae Myung.” November 13, 2025.
[2] U.S. Department of Defense. Military and Security Developments Involving the People’s Republic of China 2024: Annual Report to Congress. December 18, 2024.
[3] Ministry of Unification, Republic of Korea. North Korea Information Portal, *Chronology of Inter-Korean Relations, entry dated December 25, 2025.
The 8,700-ton figure reflects North Korea’s own description and is not an independently verified technical specification.
[4] U.S. Government Accountability Office. Military Readiness: DOD Should Take Further Actions to Address Challenges Across the Air, Sea, Ground, and Space Domains. GAO-26-108888. March 4, 2026.
[5] The White House. America’s Maritime Action Plan: Restoring America’s Maritime Dominance. February 2026.
[6] Hanwha Group. “Hanwha Announces $5 Billion Philly Shipyard Investment as Part of South Korea’s Commitment to U.S. Shipbuilding Growth.” August 27, 2025.
[7] Pennsylvania Department of Community and Economic Development. “Governor Shapiro and Secretary Siger Join Republic of Korea President Lee to Highlight Strategic Investments in the Philadelphia Navy Yard.” August 27, 2025.
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