On March 5, 2025, Bulletin of the Atomic Scientists published the executive summary of this occasional paper: “Assured distraction: How attacks on South Korea’s nuclear reactors could be a smoke screen for wider conflict.”
Earlier this month, President Trump said he looked forward to re-engaging personally with Kim Jong Un to help bring peace to the Korean Peninsula. A common fear is that North Korea might invade the South. There are, however, other military options North Korea might exercise.
Last November, NPEC held a three-day war game in which North Korea had proxies loft short-range drones against South Korea’s Kori nuclear plant, including the facility’s spent fuel storage pond. These local attacks could not clearly be attributed to North Korea and resulted in a massive radiological release. Meanwhile, China launched a military assault on Taiwan. The radiation released forced the evacuation of millions of South Koreans and Japanese across the Strait of Tsushima and kept Japan and South Korea out of the fight to protect Taiwan. It also severely stressed America security ties with South Korea and Japan.
Peace between Pyongyang and Seoul is certainly desirable. Yet, to assure it, one must consider the new ways in which North Korea might wage war against its neighbors. That was the aim of the attached war game.
As always, I’m curious to get your take.
February 20, 2025
Edited By: Henry Sokolski and Caitlyn Collett
Strategic Distraction: Pyongyang’s Proxies Target South Korea’s Reactors
By Henry Sokolski
This game was four years in the making. Originally, it presumed that China, wanting to keep America, South Korea, and Japan out of a fight over Taiwan, would ask North Korea to strike South Korea’s Kori nuclear plant. The idea here was to force a major radiological release that would prompt the evacuation of millions of South Koreans and Japanese civilians.
A brief by Joshua Stanton changed the scenario significantly. He argued it isn’t just what the North Koreans might do that you have to worry about. You also have to worry about what South Koreans sympathetic to the North might do. Mr. Stanton explained that North Korea would prefer not to take the risk of actually invading the South. Instead, he argued, Pyongyang would first try to mobilize South Koreans who favor confederating with the North to act on Pyongyang’s behalf. This insight prompted a war game adjustment: Instead of North Korea firing its missiles from over the border, the aerial attacks against Kori in the game would come from locally-lofted drones, significantly complicating attribution.
Shortly after making this change, events in South Korea validated Mr. Stanton’s judgement. Certainly, it’s difficult to understand South Korea’s impeachment proceedings without understanding that the internal debate in South Korea animating this controversy is not simply about martial law, but the optimal way to secure peace on the Peninsula. On one side of the debate are South Koreans who believe North Korea is an arch enemy that must give way eventually to a government more favorable to the South. On the other side are South Koreans who believe confederation with North Korea is a real option and the only way to produce lasting peace.
Another initial challenge in designing the game was convincing the players that attacking nuclear reactors wasn’t “crazy.” The conventional wisdom used to be that even hostile states wouldn’t want to attack these targets. Now, after Russia’s repeated attacks against Ukraine’s reactors, things are different. At a minimum, security officials in American and allied states are refusing to discuss this prospect in public, insisting that it’s too “sensitive.”
In fact, now, given Russia has threatened to attack these plants, it seems all too real. On December 31, the Russians leaked military plans that included targeting Japanese civilian infrastructure. These plans specifically listed the Tokaimura nuclear facility. Should they choose to also target the Rokkasho nuclear reprocessing plant in northern Japan, one of the largest spent nuclear fuel storage facilities in the world, it could result in nuclear spent fuel fires equivalent to several Chernobyls.
For all these reasons, this game’s three key findings deserve attention:
- Attacks against civilian nuclear plants could strategically sideline Japan and South Korea and impede the United States from effectively dealing with concurrent strategic crises in Asia. Given the multitude of Japanese and South Korean civilian infrastructure targets North Korea and China could strike, many view strikes against civilian nuclear plants as just another military option among an endless list of targeting possibilities. Nuclear power plants, however, are different. Unlike other civilian infrastructure targets, damaging these facilities can release dangerous radiation and force the evacuation of thousands to millions of people, both inside and outside the targeted country. During NPEC’s war game, locally lofted drones hit reactors and spent fuel storage ponds at South Korea’s Kori nuclear plant. This forced the evacuation of millions of both South Koreans and Japanese from affected areas and created dramatic alliance tensions. South Korea wanted to be an equal in any strike against the North. Japan was preoccupied with evacuation and humanitarian issues. The United States chose to ignore these concerns and focused instead on messaging China by unilaterally striking North Korea without consultations with Japan or South Korea. For the last seven decades, Washington has tried to protect its interests and the security of Japan and South Korea with bilateral mutual security pacts with Tokyo and Seoul. These pacts have helped deter North Korean aggression against South Korea and Chinese and Russian aggression against Japan. In this game, the pacts were not compelling enough to overcome Washington’s, Seoul’s, and Tokyo’s divergent security interests. Both the Japanese and South Korean teams were concerned that these bilateral treaties needed to be fortified with more robust trilateral arrangements. Both the South Korean and Japanese teams wanted to forge a trilateral security pact with the United States to tamp down these divergent interests. Washington, however, feared such an arrangement would limit America’s freedom of action and hinder its ability to effectively respond.
- Recommendations: America’s defense of the Western Pacific likely will turn on what Washington chooses to do. The prospects of success without finding new common interests that would work trilaterally, however, do not look bright. If the United States is unable to support a massive Reagan-style military buildup to project significant new forces in the Western Pacific, it will either have to collaborate with Seoul and Tokyo in compelling new ways, or slowly retreat
- Continued American and allied silence in peacetime about the vulnerabilities of civilian nuclear plants to overt and grey warfare increases the odds and security impacts of such attacks. Recently, leaked Russian military documents revealed intentions to attack South Korea and Japan to prevent NATO from exploiting any Russian weaknesses on its Eastern borders. These documents listed South Korean and Japanese military and civilian infrastructure targets, including Japan’s spent fuel storage and recycling facilities at Tokai Mura. If Russia struck these facilities and spent fuel fires ensued, much of Japan (conceivably many millions) would have to evacuate. Significant spent fuel pond repositories are present at many large nuclear power plant sites across South Korea and Japan. None of these sites, however, currently have any active air defenses. Nor are there yet sufficient nuclear evacuation plans. In the game, Japan pleaded with its Pacific allies and China to grant immediate humanitarian visas to displaced Japanese. On such short notice, Japan’s friends issued only limited numbers of such visas and China refused. As for the critical mission of identifying the “local” attackers of South Korea’s nuclear plant, this too was unaddressed. As one game participant, a former senior official, privately explained, public discussion and planning relating to the targeting of nuclear plants is necessarily limited as there are not yet easy ways to limit the military vulnerability of these facilities. Continued silence in these matters, however, will serve more as an invitation for attacks than as a defense. The targets, after all, are public utilities and their defense requires a substantive public brief. The United States, Japan and South Korea currently game and consult on the remote possibility of American nuclear weapons use in Asia, as the security implications of such use are so great. Yet, there has been no serious consultations or planning regarding the possible targeting of civilian nuclear facilities. This needs to change.
- Recommendations: Washington should assess the threat of Russian, Chinese, North Korean and locally staged strikes against civilian nuclear plants and facilities and game possible responses as part of routine military nuclear consultations. More generally, the United States should work with key security allies who operate their own large, domestic civilian nuclear plants and coordinate civil defense efforts to secure civilian infrastructure against grey and overt warfare attacks. Washington should conduct this effort both in classified and unclassified forums. This should be seen as a new form of cooperative threat reduction that should be conducted, as current cooperative threat reduction programs are with the close collaboration of the Defense and Energy departments.
- With gray warfare strikes against civilian infrastructure, including nuclear plants, attribution and deterrence of such attacks can no longer be assumed. What caught most of the players off guard in the game was their inability to definitively attribute the attack against South Korea’s Kori plant. Japan insisted on such proof, was unconvinced North Korea was responsible, and, so, refused to support military action against North Korea. The United States decided to act unilaterally Pyongyang without such proof. This, in turn, strained US-Japanese relations to a near breaking point. In the hot wash, several war game participants said clarifying who struck the Kori plant was critical. At the same time, the group understood that such attribution could not be assured. This, in turn, puts a premium on providing effective, proven active and passive defenses for nuclear plants that might be hit and challenges the wisdom of constructing new nuclear plants in war zones without them.
- Recommendations: The United States and its allies, individually and collectively, need to stress test any active and passive defense systems for their civilian infrastructure, including nuclear facilities, against the probability that they will not be able to attribute exactly who launched any given attack. Undoubtedly, such stress tests will spotlight major failures. It will therefore be necessary to prioritize which failures can be significantly mitigated and which can’t. This analysis, ultimately, in some basic way, needs to be made public. Unless the public understands how their public utility systems might be attacked and defended, they cannot be an active part of that effort, which is essential to their ultimate success.
To read the full paper, click here.