South Korea’s long-standing ambition to operate nuclear-powered submarines moved closer to reality in October after Donald Trump publicly signalled support for the idea. If realised, South Korea would become only the seventh country in the world to field such vessels, joining an exclusive group that includes the United States, China, Russia, France, the United Kingdom and India, CNN reported.
For Seoul, the attraction is straightforward. Nuclear-powered attack submarines can remain submerged for months, move faster over long distances and track adversary submarines far more effectively than diesel-electric boats. South Korean officials argue this capability is increasingly vital as North Korea and China expand and modernise their undersea fleets.
Why submarines matter now
The undersea balance in the Indo-Pacific is shifting quickly. China, Russia and North Korea together operate a large share of the region’s submarines, while the US Navy is retiring attack submarines faster than replacements are entering service. That strain has forced Washington to spread a limited fleet across vast oceans, from the South China Sea to waters around Taiwan.
South Korean leaders say nuclear-powered submarines would allow their navy to shoulder more responsibility closer to home, easing pressure on US forces. In theory, that would free American submarines to focus on other regional flashpoints.
Capability versus constraints
Technically, South Korea is not starting from zero. Its shipbuilders already produce advanced conventional submarines, including the Jangbogo-III class, and defence officials say the country has most of the industrial and engineering foundations needed for nuclear propulsion.
The biggest obstacle has long been political and legal. Under a decades-old civil nuclear agreement with Washington, Seoul is barred from reprocessing spent nuclear fuel, a restriction that complicates the operation of nuclear-powered vessels. Previous administrations discussed the issue quietly, but Trump’s public endorsement marked a sharp departure from that cautious approach.
Even with approval in principle, experts warn that converting ambition into steel will take time. Estimates suggest it could be a decade or more before South Korea fields its first nuclear-powered submarine.
Where the boats get built
One unresolved issue is construction. Trump suggested the submarines could be built at the Philadelphia Shipyard in the United States, recently acquired by South Korean conglomerate Hanwha. South Korean officials later indicated that discussions assumed domestic construction.
That distinction matters. Building in South Korea would maximise technology transfer and industrial gains, while construction in the US could limit access to sensitive propulsion know-how. Some analysts argue a hybrid model is more likely, with hull sections built in South Korea and nuclear propulsion systems installed in US facilities that already handle such reactors.
Regional risks and reactions
The geopolitical implications extend beyond shipyards. North Korea has condemned the plan as a step toward nuclear weaponisation, despite South Korea’s insistence that the submarines would not carry nuclear arms. Pyongyang has meanwhile unveiled its own nuclear-powered submarine project, aiming for completion by the end of 2025.
China has urged restraint, warning that such moves could undermine regional stability and non-proliferation norms. Some South Korean analysts worry that nuclear submarines could entangle Seoul more deeply in a US-led strategy to contain China, exposing it to diplomatic or economic retaliation from Beijing.
A powerful tool with trade-offs
Not everyone is convinced nuclear-powered submarines are the best answer for South Korea’s needs. Critics note that advanced diesel-electric submarines, especially those using lithium-ion batteries, can already remain submerged for extended periods in coastal waters. Nuclear propulsion, they argue, is most valuable for long-range, high-speed missions that may not align with Seoul’s primary defence requirements.
Still, supporters counter that speed, endurance and flexibility matter in any high-intensity conflict on the peninsula, particularly if Chinese or Russian submarines enter the picture.
As plans move from political statements to technical negotiations, South Korea faces a defining choice. Nuclear-powered submarines could significantly strengthen its deterrence and elevate its role within the US alliance. They could also deepen regional tensions and lock the country into a costly, decades-long commitment. The coming years will determine which path carries the greater strategic weight.
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