SEOUL — South Korea launched its first-ever nuclear-powered submarine in a live-fire ballistic missile drill on Wednesday, a watershed moment in Northeast Asian security that immediately drew condemnation from North Korea and a diplomatic protest from China.
The RSSNK Gunja — South Korea’s first 3,000-ton nuclear-powered submarine, commissioned in April with US assistance — test-fired an Hyunmoo-B ballistic missile while submerged in the Sea of Japan, the South Korean Joint Chiefs of Staff confirmed in a statement. The drill, observed by US Indo-Pacific Command officials, lasted 90 minutes and was described as a “demonstration of extended deterrence in action.”
President Lee Jae-myung watched from the underground command bunker in Pyeongtaek, calling it “a new chapter in South Korea’s defence posture.” The US State Department said the drill was “a sovereign decision” and “fully consistent with our alliance commitments.”
North Korea’s state news agency called the drill “an unforgivable nuclear provocation” and warned it would respond with “overwhelming nuclear force” if the submarine was deployed to the East Sea. China’s foreign ministry said it had “serious concerns” and called on all parties to “exercise restraint.” Japan issued a statement saying it was “monitoring the situation closely.”
The submarine represents a major leap in South Korea’s undersea capabilities — nuclear power gives it near-unlimited range and the ability to remain submerged for months, unlike the country’s existing diesel-electric fleet. South Korea is the world’s largest shipbuilder by tonnage but had previously declined to develop nuclear submarines due to US objections and non-proliferation sensitivities.
That changed in February 2026 when President Trump approved the transfer of US nuclear propulsion technology to South Korea under the revised Guidelines for Nuclear Weapon Employment, a decision first reported by Yonhap. The move broke a decades-old US policy of opposing allied nuclear propulsion programs and triggered a classified review by the International Atomic Energy Agency.
South Korea’s defence ministry said the submarine’s reactor was based on the same low-enriched uranium design approved by the IAEA and that no weapons-grade material would ever be on board. Arms control groups expressed concern, however, noting that operationalising a nuclear submarine fleet would complicate the non-proliferation landscape in Northeast Asia.
North Korea has conducted four nuclear tests and possesses an estimated 40 to 50 nuclear warheads. South Korea and the US have maintained a bilateral nuclear consultative group since 2023 but have never acknowledged US nuclear weapons on the Korean Peninsula. South Korea’s defence budget for 2026 is $47.5 billion, the largest in the country’s history.
The drill came 72 hours after North Korea test-fired two Hwasong-19 intercontinental ballistic missiles in a simulated nuclear strike on Seoul. South Korea responded by announcing the deployment of an additional THAAD anti-missile battery in Seongju county.
Regional analysts said the submarine deployment would accelerate a regional arms race in submarine capabilities, with Japan and China likely to accelerate their own programs. Australia, which is already building nuclear-powered submarines under AUKUS, said it welcomed “a stronger Indo-Pacific undersea deterrent.”
South Korea’s stock market fell 1.8 percent on the news before recovering, while the won weakened 0.4 percent against the dollar. Gold prices rose $12 per ounce as investors sought safe-haven assets amid rising geopolitical tension on the Korean Peninsula.
Sources: Reuters, AP, Bangkok Post, The Nation Thailand, BBC, Channel News Asia, Al Jazeera, Nikkei Asia, UN OCHA
Written by Kenji Tanaka, Asia Pacific Correspondent
Kenji Tanaka
Kenji Tanaka covers Asia Pacific security, technology, and geopolitics from Tokyo.