Seoul, South Korea – In a move that could redefine the balance of naval power in the Indo-Pacific, South Korea is poised to enter the elite club of nations operating nuclear-powered submarines — with the surprising and public endorsement of former U.S. President Donald Trump.
If realized, this ambitious plan would make South Korea just the seventh country in the world — joining the United States, Russia, China, France, the United Kingdom, and India — to field nuclear-powered attack submarines (SSNs). For Seoul, the goal is not just prestige; it’s strategic survival. For Washington, it could be a crucial force multiplier in an era of growing undersea threats.
A Game-Changing Capability
“South Korea already possesses the capability to build submarines of 3,000 tons or larger,” said Choi Il, a retired South Korean Navy submarine captain and defense analyst. “Our Jangbogo-III class subs are even structurally designed to allow for nuclear propulsion.”
Currently, South Korea relies on diesel-electric submarines, which must periodically surface or snorkel to charge their batteries — making them vulnerable to detection. In contrast, nuclear-powered submarines can remain submerged for years at a time, limited only by food supplies and crew endurance. They’re faster, stealthier, and far more persistent in tracking enemy vessels.
This capability would be a game-changer in monitoring North Korean submarine activity and countering China’s rapidly expanding undersea fleet, which includes over 70 nuclear-powered submarines. As North Korea advances its own submarine-launched ballistic missile (SLBM) program, Seoul’s ability to detect, track, and deter undersea threats has never been more urgent.
“Nuclear-powered subs could transform South Korea’s role within the alliance to be a more capable security provider,” said Yu Jihoon, a research fellow at the Korea Institute for Defense Analyses and former submarine officer. “The strategic implications for the South Korea–U.S. alliance are even more significant.”
Breaking the Nuclear Ceiling
South Korea has long sought nuclear-powered submarines — a dream held back by a decades-old bilateral nuclear agreement with the United States. While the agreement allows Seoul to develop civilian nuclear energy, it bans reprocessing spent nuclear fuel, a key step in creating independent nuclear propulsion capabilities.
Though past administrations discussed the issue quietly with U.S. counterparts, it was South Korean President Lee Jae-myung who took the unprecedented step of raising it openly during high-level talks with Donald Trump in late October. Lee emphasized the need for “better tracking” of North Korean and Chinese submarines and framed the request as a way to reduce the burden on U.S. forces in the region.
The response was swift — and bold.
“I have given them approval to build a Nuclear Powered Submarine,” Trump announced the next day on Truth Social, “rather than the old fashioned, and far less nimble, diesel powered Submarines that they have now.”
The statement shocked defense analysts worldwide. While Trump’s comments do not constitute formal policy, they signaled a dramatic shift in tone — one that could pave the way for a revised U.S.-South Korea nuclear cooperation agreement.
The Industrial and Strategic Stakes
Beyond defense, the submarine program promises thousands of high-paying jobs in advanced manufacturing on both sides of the Pacific. The economic ripple effects could benefit shipbuilders, engineers, nuclear experts, and defense suppliers across the U.S. and South Korea.
But the central question remains: Where will these submarines be built?
Trump claimed they would be constructed at the Philadelphia Shipyard, recently acquired by South Korean defense giant Hanwha Ocean. However, South Korean officials quickly clarified that discussions were based on the premise of domestic construction — a vital distinction.
“Building at the Philly shipyard means losing technology transfer,” warned Kim Dong-yeob, a military expert at Kyungnam University. “It is essentially no different from buying weapons built in the U.S.”
For South Korea, the goal isn’t just to own nuclear subs — it’s to master the technology, develop an indigenous industrial base, and achieve long-term strategic autonomy.
Hanwha Ocean, however, sees opportunity in collaboration. The company stated it’s “ready to provide support with its state-of-the-art shipbuilding technology” and that partnerships like the Philly yard acquisition “will contribute to the prosperity and shared security of both nations.”
Still, experts note that even state-of-the-art commercial yards like Philadelphia lack the infrastructure for full submarine construction — especially nuclear-powered vessels. The U.S. has only two shipyards capable of building nuclear subs: General Dynamics Electric Boat and Huntington Ingalls’ Newport News Shipbuilding — both already at full capacity modernizing the American fleet.
“Most likely, we’ll see modular construction,” said maritime historian Sal Mercogliano of Campbell University. “Large sections built in Korea or the U.S., with the nuclear reactor and propulsion systems assembled domestically in the U.S. due to security and technical expertise.”
A Decade-Long Journey Ahead
Even if political and technical hurdles are cleared, experts estimate it will take at least 10 years before South Korea operates its first nuclear-powered submarine.
The U.S. Department of Defense has pledged to work closely with the Departments of State and Energy to implement the president’s commitment, but key questions remain:
- Will the U.S. allow full technology transfer, or only supply enriched fuel?
- Can Seoul navigate congressional approval and non-proliferation concerns?
- How will Japan and other regional powers react to a nuclear-armed submarine capability, even if it’s for propulsion, not weapons?
Meanwhile, South Korea continues to advance its conventional undersea edge. In October, it launched the 3,600-ton Jang Yeongsil, hailed by the country’s Defense Acquisition Program Administration (DAPA) as the “world’s best diesel submarine.” Built by Hanwha Ocean, it features cutting-edge lithium-ion batteries, enabling longer, quieter underwater operations than traditional subs.
Still, diesel-electric subs cannot match the endurance and speed of nuclear-powered vessels — especially in deep waters and prolonged surveillance missions.
A New Chapter in the Alliance
The prospect of South Korea joining the nuclear submarine club marks more than a technological leap — it signals a maturation of the U.S.-South Korea alliance. As Adm. Philip Davidson warned in 2019, 160 submarines from China, Russia, and North Korea patrol the Indo-Pacific, while the U.S. retires SSNs faster than it replaces them.
With only 49 attack submarines in its fleet — two-thirds of which are potentially available in a crisis — the U.S. Navy is stretched thin. A capable South Korean SSN fleet could shoulder more of the regional burden, allowing U.S. subs to focus on critical zones like the South China Sea and waters around Taiwan.
In many ways, this isn’t just about submarines — it’s about strategic rebalancing in a region where undersea dominance could determine the outcome of future conflicts.
As Yu Jihoon put it: “This isn’t just about national defense. It’s about Seoul stepping up as a security provider in a volatile region.”
With Trump’s blessing, South Korea may finally be on the verge of making its nuclear-powered dream a reality — one hull at a time.
