South Korea's nuclear submarine gamble raises prospect of underwater arms race in Asia

South Korea’s pursuit of nuclear-powered submarines is gaining traction following U.S. President Donald Trump’s endorsement, ending decades of U.S. resistance in a move that could reshape Asia’s security landscape and escalate an underwater arms race.
Seoul has long sought to join the elite group of nations operating nuclear submarines to counter North Korea. Trump’s approval removed a key barrier by granting access to fuel under a nuclear agreement between the countries.

Still, South Korea’s rapidly developing program could irk China and pressure Japan to develop similar capabilities, analysts and former military officials say.

“Submarines are highly effective attack systems. An arms race in the region is inevitable,” said Choi Il, a retired South Korean Navy submarine captain. Seoul argues nuclear propulsion is crucial to counter North Korea’s undersea threats, including submarine-launched ballistic missiles. It has repeatedly said it will not acquire nuclear weapons and respects the non-proliferation regime.

South Korean President Lee Jae Myung on Wednesday described the deal as a major achievement from his meeting with Trump and said it would enhance security flexibility and defense autonomy.

North Korea claims to be developing similar capabilities, with state media showing leader Kim Jong Un inspecting what it said was a nuclear-powered submarine in March. How advanced its program is remains uncertain, but some analysts suspect Pyongyang is receiving Russian assistance, a possibility that South Korea’s military has said it is closely monitoring.

Russia and North Korea have said they are beefing up defense cooperation, but have not provided details on technical cooperation on defence.

Countering China
South Korean lawmaker and defense expert Yu Yong-weon said, since nuclear-powered submarines are faster and can remain underwater far longer than diesel-powered equivalents, they would enhance monitoring of North Korean submarines.