Would South Korean nuclear weapons enhance or erode Northeast Asia’s security?

South Korean President Yoon Suk-yeol recently raised eyebrows in Washington when he said his country might consider developing its own nuclear deterrent, rather than relying exclusively on America for nuclear protection.

U.S. officials scrambled to assure Seoul officials there is no need to develop their own nuclear weapons since the U.S.-Republic of Korea Mutual Defense Treaty encompasses all threats to its security, including a nuclear attack.  

To reinforce the point, Washington and Seoul announced last week they will hold a tabletop exercise this month to develop “response options to deal with the DPRK [North Korean] nuclear threat.”  

America’s “extended deterrence” means that U.S. nuclear weapons could be used to defend South Korea if such weapons were ever used against it, and they already serve a deterrent purpose in preventing such a scenario in the first place.

But recent public opinion polls show that, strong as U.S.-ROK security relations seem, many South Koreans harbor doubts that Washington would actually enter a nuclear war and risk a calamitous nuclear attack on U.S. forces or assets in the region, or even on the American homeland, all just to defend South Korea.

In a poll last year, 71 percent of South Koreans supported developing an indigenous nuclear capability. Reflecting that reality, retired Lt. Gen. In-Bum Chun, former commander of the Republic of Korea Special Warfare Command, said, “Right now we have the United States that provides us with a nuclear deterrent. But we are more concerned than we used to be. Korean people are looking for answers.” 

The increased South Korean angst partly reflects Pyongyang’s technological progress in its nuclear and missile programs, greatly facilitated by China’s economic and diplomatic support — despite Beijing’s, and Henry Kissinger’s, protestations that it shares the West’s concerns about a nuclear North Korea. 

Confidence in the strength of the U.S. commitment also has been undermined by the actions and inaction of the three most recent American administrations.

First was the Obama-Biden failure to confront China on its broken promise not to militarize its artificial islands in the South China Sea, or its breach of a U.S.-mediated agreement on the Spratly Islands dispute with the Philippines, a U.S. ally. (Nor did President Obama act against Russia over its intervention in Syria to protect Bashar al-Assad from Obama’s “red line”or its 2014 invasion of eastern Ukraine and Crimea.) 

The credibility of the American commitment to South Korea suffered a direct blow with former President Trump’s harsh disparagement of the U.S.-ROK alliance and Seoul’s reliability as an ally. He questioned its willingness to bear a fair share of the defense burden, accusing it essentially of free-loading off the U.S. security blanket — the same charge he made against Japan and members of the North Atlantic Treaty Organization. His unbridled criticism went so far as to threaten termination of the U.S.-ROK alliance as an unfair and unnecessary imposition on the United States.

The Biden administration has added to South Korean doubts about U.S. resolve. In addition to sharing the Obama-Biden legacy on foreign policy, which he led as Obama’s vice president, President Biden added his calamitous troop withdrawal from Afghanistan in 2021. That was followed by his administration’s failure to deter Russia’s 2022 invasion of Ukraine, despite touting that it knew Russia’s plans well in advance.  

Nor has Biden been willing either to intervene directly or to provide Ukraine with the advanced weapons systems it requires, because Vladimir Putin might see it as escalation that could precipitate World War III.  

Finally, there is the matter of Taiwan, under direct and escalating threat from China, and the deepening economic and political relationship between Taiwan and the U.S. that started under the Trump administration and has continued under Biden.

Despite Biden’s episodic expressions of intention to defend the island against Chinese aggression, he, like his predecessors, refuses to state a declarative U.S. commitment to defend Taiwan, preferring to retain the policy of strategic ambiguity.

Given that spotty record of U.S. steadfastness on behalf of allies and security partners, it is not surprising that some South Koreans see potential leaks in Washington’s nuclear umbrella and wish to add their own nuclear deterrent.  

As Jenny Town, a senior fellow at the Stimson Center and director of Stimson’s 38 North Program, recently observed, “Given all of the advancements that North Korea has made in their nuclear weapons program, and changes in the geopolitical environment, there’s been a lot more anxiety in South Korea about how they deal with a nuclear North Korea — and what the U.S. would actually do.”

At a recent Stimson conference on “assessing the risks” of a South Korea nuclear weapons program, experts coalesced around the idea that the country would be less safe with its own nukes. The concern was expressed that a competition between two nuclear powers on the Korean Peninsula would increase the danger of war because of the risk of escalation from the use of conventional to nuclear weapons. The experience of the U.S.-Soviet confrontation during the Cold War runs counter to that fear, and arguably reduced the prospect of conventional war precisely because of the danger of nuclear escalation.

It was also asserted that South Korea’s acquisition of nuclear weapons would fracture the U.S.-ROK alliance, though why that would happen is not self-evident. While Washington would not be happy that its advice was spurned, the importance of South Korea to regional stability and its value as a loyal ally would hardly be diminished because it became a nuclear power.

The experts correctly noted that South Korea’s withdrawal from the Non-Proliferation Treaty would further weaken the NPT, but the question is whether that would be worse than nuclear weapons on the Korean Peninsula being wielded only by an aggressive North Korea, supported by China, its aggressive nuclear-armed ally.

Kissinger testified on North Korea’s nuclear program before the Senate Armed Services Committee in January 2018: “[I]f North Korea could keep its capability in the face of opposition by China and the United States … South Korea and Japan will want nuclear weapons too, and then we are living in a new world … that will require new thinking.”

Kissinger’s premise of Chinese “opposition” to North Korea’s nuclear program is unfounded. But we are now approaching that “new world” he predicted and new thinking is indeed in order.

Joseph Bosco served as China country director for the secretary of Defense from 2005 to 2006 and as Asia-Pacific director of humanitarian assistance and disaster relief from 2009 to 2010. He served in the Pentagon when Vladimir Putin invaded Georgia and was involved in Department of Defense discussions about the U.S. response. Follow him on Twitter @BoscoJosephA.