North Korean leader Kim Jong Un has inspected the construction of a massive 8,700-ton “nuclear-powered strategic guided missile submarine,” according to state media KCNA. The reported vessel, depicted in a shipyard in red primer, represents a potential leap toward a far more survivable, sea-based nuclear arsenal, complicating allied defenses and raising the stakes for regional stability.
On December 25, 2025, the world received a stark reminder of North Korea’s relentless military ambitions. State media released images and a report detailing Kim Jong Un’s visit to a domestic shipyard to inspect a colossal new submarine under construction. If the claims hold true, this isn’t just an incremental upgrade; it’s a platform designed to fundamentally alter the strategic calculus on the Korean Peninsula.
The broadcasted images show a hull of formidable size, reported KCNA, coated in red anti-corrosion primer and sitting on a building cradle. The most striking feature is an exceptionally long sail that dominates the upper hull, fitted with what appear to be at least five—and potentially up to ten—vertical launch tube hatches. Analysts suggest these tubes could be designed for the Pukguksong-XA submarine-launched ballistic missile, which was showcased earlier this year, though this remains unconfirmed. The design seems to be a purpose-built strategic asset, a significant evolution from North Korea’s previous approach of modifying older, 3,000-ton diesel-electric submarines.
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Kim Jong Un, the Supreme Leader of North Korea, described the project as pivotal to the country’s defense plans. The official report explicitly labels it a “nuclear-powered” vessel. This single claim, if realized, is the game-changer. A nuclear reactor would allow the submarine to operate submerged for months, evading detection far more effectively than vessels that must regularly surface to run diesel engines and recharge batteries. This survivability is the core of a credible second-strike nuclear capability, a longstanding goal for Pyongyang.
The technical details visible in the images hint at a sophisticated design. The hull lacks visible limber holes, suggesting a sleek, single-hull form for reduced noise and drag—a feature of modern submarines. A long, recessed array along the flank likely houses a conformal sonar, complementing a large bow sonar dome. Furthermore, the sail showcases modern optronic and communication masts. Notably, according to KCNA, there is no visible snorkel mast, a configuration consistent with a nuclear-powered design that doesn’t require atmospheric air for propulsion.
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Of course, monumental questions remain. The world has no independent verification that North Korea has successfully developed a small, reliable, and safe naval nuclear reactor. “The existence and maturity of any naval reactor have not been confirmed from open sources,” caution proliferation experts. Building the hull is one thing; integrating a functioning reactor, a competent crew, and reliable missiles into an operational weapon system is a challenge of a different magnitude. It could be years, if ever, before this vessel conducts an actual deterrent patrol.
Nevertheless, the mere pursuit of this capability forces regional powers to prepare. For South Korea, Japan, and the United States, a nuclear-armed North Korean submarine at sea would be a nightmare scenario. It is a mobile, hidden launch platform that would demand a massive, continuous investment in anti-submarine warfare assets—aircraft, ships, and submarines—to track and monitor. This complicates military planning and increases the risk of miscalculation during a crisis.
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The submarine also features six forward torpedo tubes, indicating a dual-purpose role for both strategic strike and conventional sea-denial missions. This blend of capabilities makes it a versatile, and therefore more threatening, platform. While one submarine does not constitute a full sea-based deterrent, which would require several hulls, it represents a clear statement of intent. North Korea is methodically working to ensure its nuclear weapons can survive a first strike and retaliate, thereby aiming to solidify its status as a nuclear power that cannot be ignored.
