North Korea Now Has a Nuclear Submarine—And There’s Only One Place They Could Have Gotten It From
North Korea’s indigenous technological base is clearly insufficient to have developed the submarine on its own—almost certainly meaning that Pyongyang sought help from Russia.
Recently, North Korea unveiled what it claimed was its first nuclear-powered submarine. Specifically, Pyongyang described the large new submarine as a “nuclear-powered strategic guided missile submarine”—claiming that it was capable of carrying up to ten nuclear weapons, potentially with a range that could threaten the American mainland.
The initial reports proliferated from the North Korean Central News Agency (KCNA), Pyongyang’s primary propaganda arm. If its claims are true, the submarine is a significant evolution in the development of North Korea as a major nuclear weapons state. Indeed, this system would provide Pyongyang with decisive advantages over their South Korean neighbors, who lack nuclear weapons capabilities, let alone a sea-based nuclear capacity.
North Korea’s History of Nuclear Expansion
South Korean experts have assessed that the alleged North Korean nuclear submarine is a 6,000-to-7,000-ton submarine—roughly twice the size of North Korea’s last conventional submarine, the Hero Kim Kun Ok, which was first introduced in 2023. The North Korean description of the new submarine as being a “strategic-guided missile submarine” indicates that it will likely launch nuclear weapons such as the Pukguksong-6 missile, which Pyongyang claims has a range of nearly 7,500 miles.
If operational, such a submarine would ensure that North Korea has a second-strike capability, allowing it to launch retaliatory nuclear strikes from underwater—an ability that is notoriously difficult to detect and counter.
The timing of this unveiling is purposeful. It comes amidst heightened tensions on the Korean Peninsula, with the United States and South Korea—on the heels of significant internal political instability—conducting their annual Freedom Shield exercises in March 2025. These drills are regularly condemned by Kim Jong-un’s government as provocative, and Pyongyang regularly tests its own weapons in response.
This year, in response to the Freedom Shield exercises, Kim Jong-un swore to exponentially increase his nuclear arsenal and rejected calls from the G7 for North Korea to denuclearize. More ominously, the submarine’s unveiling comes during a time in which Russia and North Korea have been deepening their ties. Indeed, Russia may have provided key technical assistance to Pyongyang, possibly in exchange for North Korean conventional weapons and troops to support its war efforts in Ukraine.
Yet Russia’s specific involvement remains murky on the submarine issue. Still, given how badly Russia needed North Korea’s assistance, Kim was likely able to drive a hard bargain—possibly even getting Moscow to hand over at least some of its own highly guarded nuclear secrets.
Moscow’s Growing Relationship with Pyongyang
This defies decades of Moscow’s being reticent to share such advanced technology with North Korea. At the height of the Cold War, for example, the Kremlin routinely refused to share advanced submarine technology. But the Ukraine War, and Moscow’s ensuing international isolation, fundamentally altered such calculations.
North Korea’s existing technological base, and its ceaseless reliance on outdated systems, strongly suggests that it lacks the indigenous capacity to develop a nuclear-powered submarine on its own. If Russian aid were to be confirmed, it would yet again show how deep Moscow and Pyongyang’s relationship has become—and how unproductive an attempt by the Trump administration to restart talks with Pyongyang would likely be.
By giving North Korea technical assistance for developing a nuclear submarine, Moscow is also complicating American interests, and the interests of their allies in the Indo-Pacific. Unlike its diesel-powered fleet of antique submarines, a nuclear-powered vessel could remain submerged for extended periods, enhancing its survivability and stealth. This would complicate missile defense efforts by the United States, South Korea, and Japan, forcing a serious reevaluation of regional security postures.
Could North Korea Be Lying About the Submarine?
There are understandably many who are skeptical of North Korea’s claims. Pyongyang’s current submarine fleet, numbering between 70 and 90 submarines, are mostly based on obsolete Soviet designs, such as the Romeo-class diesel-powered subs from the 1950s. Building a nuclear-powered submarine requires advanced technology.
Skeptics have noted that in order to successfully construct a nuclear submarine, North Korea would need a miniaturized nuclear reactor, sophisticated propulsion systems, and the ability to manage nuclear fuel. They argue that North Korea, which is heavily sanctioned and resource-strapped, has failed to demonstrate such capabilities.
Unfortunately, the naysayers are probably wrong. Since 2013, Pyongyang is believed to have possessed the necessary miniaturization technology. Furthermore, it is very likely that if Moscow gave anything to Pyongyang, it was advanced submarine propulsion technology. This was, after all, the same technology that U.S. analysts suspect Moscow handed over to Beijing last year as part of their “friendship with no limits.” With Moscow endeavoring to form what the Wall Street Journal refers to as the “CRINK” (China, Russia, Iran, North Korea) alliance, circumventing Western sanctions is nowhere near as difficult as it was even five years ago.
Over the past decade, North Korea’s overall nuclear weapons program has progressed steadily, despite the resistance from the West. While the Kim regime may not be able to feed its people or spread the trappings of modernity beyond its privileged elite class, by throwing all resources and efforts into developing a robust, reliable nuclear weapons program, it has ensured that it will, at the very least, have a nuclear stopgap against possible American-led regime change efforts.
North Korea’s Subs Mean Trouble for America
Nevertheless, the skeptics are right when they argue that building, maintaining, and operating nuclear-powered submarines are highly complex affairs—and that North Korea has no experience with this. Even the far more competent Chinese navy recently demonstrated it is still going through its own learning struggles; its newest nuclear submarine accidentally sunk after a sailor apparently left a hatch open during docking, sending it to the bottom of the drink.
If even China, with its monstrous economy and highly advanced technological and industrial base, can make such mistakes with their nuclear-powered submarines, then North Korea will have some significant catching up to do.
But the threat of North Korea’s nuclear-powered submarines should not be ignored or discounted. It is real. Over time, it will become more serious.
About the Author: Brandon J. Weichert
Brandon J. Weichert, a Senior National Security Editor at The National Interest as well as a contributor at Popular Mechanics, who consults regularly with various government institutions and private organizations on geopolitical issues. Weichert’s writings have appeared in multiple publications, including the Washington Times, National Review, The American Spectator, MSN, the Asia Times, and countless others. His books include Winning Space: How America Remains a Superpower, Biohacked: China’s Race to Control Life, and The Shadow War: Iran’s Quest for Supremacy. His newest book, A Disaster of Our Own Making: How the West Lost Ukraine is available for purchase wherever books are sold. He can be followed via Twitter @WeTheBrandon.
Image: Shutterstock / Jasmine Leung.