SEOUL, South Korea — An escalating arms race for nuclear-powered submarines is underway between North and South Korea, fueled by shifting U.S. security strategies in the region. North Korea revealed images Thursday of what it calls an “8,700-ton nuclear-powered strategic guided missile submarine,” marking the first time the country has disclosed the vessel’s tonnage and apparently completed hull since announcing its pursuit of such submarines in 2021.
The unveiling comes as South Korea rapidly advances its own plans to build a fleet of nuclear submarines, a move greenlit by the U.S. in October. But experts say the submarine buildup isn’t solely about deterring North Korea—it’s also a response to China’s growing naval power.
In this undated photo provided Thursday, Dec. 25, 2025, by the North Korean government, its leader Kim Jong Un inspects a nuclear-powered submarine under construction at an undisclosed location in North Korea. Independent journalists were not given access to cover the event depicted in this image distributed by the North Korean government. The content of this image is as provided and cannot be independently verified. Korean language watermark on image as provided by source reads: “KCNA” which is the abbreviation for Korean Central News Agency.
AP/KCNA via KNS
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AP/KCNA via KNS
Kim Jong Un declared the new submarine would bolster his country’s defenses against what he called a “negative security situation.” He also criticized South Korea’s plans to build its own nuclear submarines, labeling them an “offensive act.”
A Regional Power Shift
The escalating submarine race isn’t happening in a vacuum. The U.S. has increasingly urged its allies to shoulder more of their own defense burdens, and South Korea’s move to develop nuclear submarines received a key endorsement from Washington in October. But analysts say the buildup is also a direct response to China’s growing military presence in the region.
South Korea’s defense minister, Ahn Gyu-back, said in October that conventional submarines simply can’t match the endurance and speed of nuclear-powered vessels, particularly in the face of North Korea’s advancements.
Admiral Daryl Caudle, the chief of naval operations of the U.S. Navy, said during a visit to Seoul in November that he anticipates South Korean nuclear submarines will be used to counter China’s influence in the Indo-Pacific, in addition to addressing the North Korean threat.
Retired South Korean navy captain Yoon Sukjoon says it’s “a given” that South Korean nuclear submarines will operate beyond the Korean Peninsula, noting that the waters around Korea are too shallow for effective submarine operations. “If the South Korean Navy expands its nuclear submarine operations to China,” he says, “it can contribute some strategic deterrence against the Chinese Navy’s threats in the Indo-Pacific.”
However, South Korea is treading carefully, wary of provoking China—its largest trading partner. President Lee’s office later clarified that his remarks to Trump referred to submarines operating “near our waters toward the direction of the North and China,” not vessels specifically targeting China.
Public opinion in South Korea reflects this caution, with a recent survey showing a majority of South Koreans believe their country should remain neutral in a potential conflict between the U.S. and China.
Political scientist Kim Heungkyu, director of the China Policy Institute at Ajou University, argues that South Korea and Japan are increasingly concerned about China’s growing influence and are seeking to reduce their reliance on U.S. security guarantees as the U.S. shifts its focus closer to home.
A recent poll by the Asan Institute found that less than half of South Koreans believe the U.S. would respond with nuclear weapons if North Korea launched a nuclear attack. A majority also expressed support for South Korea developing its own nuclear weapons, even if it meant facing international sanctions or the withdrawal of U.S. troops.
“In a new international order without the U.S. in the Western Pacific, South Korea needs a survival strategy based on nuclear weapons,” Kim says. He adds that nuclear-powered submarines represent an “entry point toward a much bigger goal” of nuclear armament.
The South Korean government has denied any intention of pursuing nuclear weapons, even as it seeks access to U.S. assistance with uranium enrichment and spent fuel reprocessing.
