Nuclear submarine arms race heats up between North and South Korea : NPR
In this undated photo provided Thursday, December 25, 2025 by the North Korean government, its leader Kim Jong Un inspects a nuclear-powered submarine under construction in 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. The Korean watermark on the image provided by the source reads: “KCNA”, which is the abbreviation for Korean Central News Agency.
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SEOUL, South Korea — The arms race for nuclear-powered submarines is accelerating between North and South Korea, amid changes in U.S. security strategy in the region.
North Korean state media on Thursday revealed a photo of what it called an “8,700-ton nuclear-powered strategic guided missile submarine.” This is the first time North Korea has disclosed the submarine’s tonnage and apparently completed hull since declaring its search for nuclear submarines in 2021.
North Korean leader Kim Jong Un said the new ship would help defend his country against “the negative security situation that has become a current reality,” according to the country’s state media. Kim criticized South Korea’s plan to build its own nuclear submarines as “an offensive act…that must be countered.”
South Korea has been rapidly building its own nuclear submarines since receiving approval from President Trump in October. A whole-of-government task force was launched last week in Seoul, while the country’s national security adviser, Wi Sung-lac, said South Korea would work on a pact for the United States to supply it with nuclear fuel for military use.
The green light for South Korea’s undersea ambitions came as the United States pushes its allies to shoulder more of their own security burden and spend more to bolster their defense capabilities.
South Korea has for decades sought to build nuclear submarines to counter North Korea’s nuclear threats, which have rapidly expanded into the maritime sphere in recent years. In addition to manufacturing the nuclear-powered submarine, it tested nuclear missiles launched from submarines and claimed to have developed a nuclear-capable torpedo.
South Korean Defense Minister Ahn Gyu-back said in October that conventional diesel-powered submarines “cannot compete with the nuclear submarines that North Korea is building in terms of underwater endurance and speed.”
US expects submarines to help counter China
The United States expects future South Korean nuclear submarines to do more in the region than counter North Korea. Admiral Daryl Caudle, the U.S. Navy’s chief of naval operations, said during his visit to Seoul in November that it was “a natural expectation” that they would be used “to achieve our combined objectives on what the United States considers to be our primary threat, which is China.”
In this undated photo provided Thursday, Dec. 25, 2025, by the North Korean government, its leader Kim Jong Un, third from left, visits a shipyard as he 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. The Korean watermark on the image provided by the source reads: “KCNA”, which is the abbreviation for Korean Central News Agency. (Korean Central News Agency/Korea News Service via AP)
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South Korean President Lee Jae Myung appeared to live up to that expectation, rarely mentioning China during his summit with Trump in October. “The limited underwater range of diesel submarines restricts our ability to track submarines on the North Korean or Chinese side,” he said.
Yoon Sukjoon, a retired South Korean navy captain, told NPR that it is “a given” that South Korean nuclear submarines will operate in a broader underwater domain beyond the Korean Peninsula.
Yoon says the waters around the peninsula are too shallow for underwater operations. “But if the South Korean navy expands its nuclear submarine operations to China,” he says, “it can contribute to some strategic deterrence against Chinese naval threats in the Indo-Pacific.”
But South Korea is reluctant to suggest a military confrontation with China – its largest trading partner, because China is also rapidly expanding its navy. President Lee’s office later said his remarks to Trump “simply referred to submarines near our waters heading to the North and China,” not ships owned by certain countries.
The government’s cautious stance reflects the attitude of the South Korean public, a majority of whom say South Korea should remain neutral if a serious conflict breaks out between the United States and China, according to a recent survey.
“Entry point to a much bigger goal”
But South Korea — and Japan, which has signaled a desire to develop nuclear-powered submarines — are also concerned about China’s growing sphere of influence and do not want to fall into it, said Kim Heungkyu, a political scientist and director of the Institute of Chinese Politics at Ajou University.
As the United States refocuses its defense policy domestically, he says, its allies are increasingly wary of its security commitment in Asia.
In a March poll by the private think tank Asan Institute, fewer than half of Koreans said they believed the United States would respond with nuclear weapons if North Korea attacked the South with such a weapon. At the same time, a majority of South Koreans said they support nuclear weapons, even at the cost of international sanctions or the withdrawal of American troops.
“In a new international order without the United States in the Western Pacific, South Korea needs a survival strategy based on nuclear weapons,” Kim says. And, he adds, nuclear-powered submarines would offer the country an “entry point to a much larger goal”: nuclear weapons.
The South Korean government, which is separately seeking access to uranium enrichment and spent fuel reprocessing in negotiations with the United States, has denied it wants to go nuclear.
But Kim says the Trump administration is “pushing South Korea and Japan toward nuclear weapons, whether it likes it or not.”
NPR’s Anthony Kuhn contributed to this report from Seoul.
