Construction of a nuclear-powered submarine as revealed by North Korea. / Rodong Sinmun

North Korea’s newly revealed nuclear-powered submarine, first disclosed in early March, is estimated by experts to weigh between 6,000 and 7,000 tons and is believed capable of carrying both submarine-launched ballistic missiles (SLBMs) and submarine-launched cruise missiles (SLCMs) simultaneously.

 This submarine would pose a tangible threat to South Korea and the United States if deployed. Some analysts believe the timing of its public reveal is a calculated move by North Korea to secure a strategic advantage ahead of potential talks with the Trump administration.

 According to the Korea Institute for Defense Analyses (KIDA) on Tuesday, Lee Sang Kyu, Director of the Nuclear Security Research Office, and Research Fellow Shin Seung Ki stated in their recent assessment that “the nuclear-powered strategic guided-missile submarine revealed by North Korea is estimated to be in the 6,000–7,000 ton range, which is similar in scale to some nuclear submarines operated by China and the United Kingdom.”

 For context, the U.S. Navy’s Los Angeles-class attack submarines displace around 6,000 tons, indicating that North Korea may be constructing a submarine of similar or even larger size. South Korea’s most advanced non-nuclear submarines are about 3,000 tons.

 North Korea first disclosed the construction of the nuclear-powered submarine on March 8 through the <em>Rodong Sinmun.</em> Although this project had been listed as one of the five major goals in the five-year defense development plan announced during the 8th Party Congress in August 2021, this is the first time the actual existence of such a vessel has been confirmed.

 North Korea has not disclosed detailed specifications of the submarine. However, it appears to be significantly larger than the Kim Kun Ok Hero submarine, which was introduced in September 2023 as the country’s first tactical nuclear attack submarine. Its propulsion system is believed to have been upgraded to nuclear power.

 The researchers analyzed that “the submarine disclosed by North Korea is highly likely to carry medium- to large-sized missiles, and given the term ‘strategic guided missile’ used in the announcement, it is expected to be equipped with 6 to 12 SLBMs and around 10 SLCMs simultaneously.”

 However, they also estimated that it would take at least 10 more years before such a submarine becomes operational. Submarine reactors use highly enriched uranium (HEU) or uranium enriched to over 20 percent as fuel, and a test reactor must be constructed to validate and test such a system. Currently, there is no indication that North Korea has begun this phase.

Kim Jong Un inspected the construction of the nuclear-powered submarine. / Rodong Sinmun

It is believed that North Korea may have already sought, or is highly likely to seek, technical support from Russia to address technical challenges in the construction process or to accelerate development. Should Russia provide nuclear propulsion technology, development could proceed more rapidly.

 The researchers suggest that North Korea may have revealed its nuclear-powered submarine project as a strategic move to gain leverage in future negotiations with the United States. Before unveiling the submarine, North Korea showed its uranium enrichment facilities in September 2024 and January 2025, which may have been intended to present its nuclear capabilities as a fait accompli and secure a dominant position in negotiations.

 The researchers stated, “North Korea has a strong incentive to steer negotiations with the United States away from complete denuclearization and toward smaller deals, nuclear arms control, and risk reduction.” They added, “By showcasing its nuclear deterrence through the development of a nuclear-powered submarine while leaving the door open to dialogue, North Korea is likely trying to pressure the United States.”

 If deployed, a nuclear-powered submarine would significantly extend North Korea’s operational range and endurance compared to diesel-electric submarines, enabling far-reaching missions. Such capabilities are expected to present new challenges to South Korea-U.S. anti-submarine warfare operations.

 The researchers concluded, “North Korea’s development of a nuclear-powered submarine will become a key variable in the security landscape not only for the U.S. but also for South Korea, Japan, and the Western Pacific region.” They also warned that “beyond military intent, the submarine could be used as a tool to weaken confidence in the U.S. extended deterrence and to create division between South Korea and the United States.”

North Korea’s newly revealed nuclear-powered submarine, first disclosed in early March, is …

North Korea’s Nuclear Submarine: A New Threat to the U.S. and South Korea