North’s nuclear sub nears completion; Seoul must move faster on counterstrategy

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North’s nuclear sub nears completion; Seoul must move faster on counterstrategy

Published: 26 Dec. 2025, 00:00

Audio report: written by reporters, read by AI

North Korean leader Kim Jong-un inspects on-site the construction of an 8,700-ton nuclear-powered strategic guided missile submarine, according to a report by the Korean Central News Agency on Dec. 25. [KOREAN CENTRAL NEWS AGENCY/YONHAP]

North Korea revealed on Christmas Day that it is building an 8,700-ton nuclear-powered submarine, suggesting that the vessel is approaching the final stages of external construction. State media said Kim Jong-un had inspected the project alongside his daughter, widely known as Kim Ju-ae. The submarine was described as a “nuclear shield” and a “nuclear-powered strategic guided missile submarine.”

Photographs released by North Korean media show that the submarine’s outer structure is largely complete. Submarines are typically built by assembling external hull blocks before installing internal systems, meaning that visible progress on the exterior usually indicates that construction has advanced considerably. If the assessment is accurate, North Korea may be nearing the point of possessing a nuclear-powered ballistic missile submarine, or SSBN. That would place it far ahead of Korea, which has only recently begun debating the introduction of nuclear-powered submarines.

Pyongyang did not disclose the date of Kim’s inspection, raising the possibility that the announcement was timed deliberately. It may have been intended as a “Christmas message” to the United States, while also responding to remarks made a day earlier by national security officials in Seoul that South Korea and the United States had agreed on the need for a separate bilateral arrangement related to cooperation on nuclear-powered submarines. Kim has previously denounced South Korea’s pursuit of such vessels as an attack on maritime sovereignty and a security threat requiring a firm response. The irony is hard to miss: North Korea is criticizing a program South Korea has yet to begin while unveiling a submarine whose exterior appears nearly complete.

The more pressing issue is South Korea’s security reality. Since taking power, Kim Jong-un has focused relentlessly on advancing nuclear and missile capabilities. A nuclear-powered submarine would represent another major leap. Such vessels can theoretically remain submerged for extended periods, making them extremely difficult to detect once deployed. If armed with nuclear warheads, they could threaten not only nearby South Korea but also targets at much greater distances, including the United States. Dismissing these developments on the grounds that North Korean weapons remain unproven would be a mistake. Military authorities must accelerate the development of strategies and tactics suited to this emerging threat and move swiftly to secure weapons systems capable of countering it.

Many analysts argue that North Korea, constrained by years of economic hardship, lacks the industrial base to develop such technology independently. Attention therefore turns to Russia, with whom Pyongyang has drawn closer since the outbreak of the war in Ukraine. The resemblance between the reported 8,700-ton submarine and Russia’s Akula-class SSBNs has fueled speculation of external assistance. Seoul should now mount a full diplomatic effort to block deeper military cooperation between North Korea and Russia. Strengthening deterrence through the South Korea-U.S. alliance and combined forces is essential. Given the possibility of technology acquisition through cyber means, coordinated measures are also needed to prevent illicit transfers involving domestic and foreign defense firms.

Ultimately, the most effective counter to a nuclear-powered submarine is possessing the same class of vessel. The push by Lee Jae Myung to introduce nuclear-powered submarines should therefore proceed with greater urgency.

This article was originally written in Korean and translated by a bilingual reporter with the help of generative AI tools. It was then edited by a native English-speaking editor. All AI-assisted translations are reviewed and refined by our newsroom.