Amidst a cascade of increasingly bellicose behavior, Kim Jong Un has accepted a new political reality on the Korean Peninsula. Instead of seeking the peaceful unification of Korea under North Korean leadership, Kim has declared the South Korea (ROK) to be a foreign and hostile nation, and the North’s “primary foe and invariable principal enemy.” He has backed these words with actions that clearly reflect his frustration over losing the unification competition, including demolishing inter-Korean roads and rail lines, deploying landmines, and firing artillery into disputed areas. The reasons for Kim’s policy shift lie in the increasingly visible solidification of United States-South Korea cooperation. These developments have demonstrated that there is little chance of peeling the South away from its U.S. ally, and that taking the South by force would be a losing proposition. Key factors include increased military sales, frequent joint exercises, and the launch of the U.S.-ROK Nuclear Consultative Group (NCG), which enhances extended nuclear deterrence commitments and integrates the ROK into contingency planning.
The provocative behavior and rhetoric on the peninsula have increased fears of a large-scale conflict between the two Koreas that would certainly draw in the United States, which is bound by a 1953 mutual defense treaty and currently has forces stationed in South Korea. This raises a critical question about the role of the United States’ nuclear umbrella in defending the ROK against a nuclear or large-scale conventional attack from North Korea (DPRK). While this is a complex issue with a long history, the answers are simpler than many realize. The United States can meet the twin goals of deterring the DPRK and assuring its ROK allies by remaining committed to a deterrence strategy backed by U.S. nuclear capabilities.
Strengthening U.S. Policy
Strategic deterrence on the Korean Peninsula is more stable than many realize, as Dr. Terry Roehrig and Dr. David Logan of the U.S. Naval War College highlight in a recent report. This is largely because any large-scale conflict would “likely be the end of the Kim Regime, and it is hard to imagine Pyongyang could see otherwise.” In this light, Kim Jong Un’s recent behavior is not a surprise, but the predictable reaction of a frightened actor who recognizes that he is at a significant strategic disadvantage. Though Kim’s decision-making process is opaque, and his behavior appears dangerous, it would be an oversimplification to label him as unhinged or irrational. Aggressive or risky behavior is possible among rational actors if it aligns with their goals. In fact, Kim relies on a clear deterrence strategy. His conditional threats are classic formulations of deterrence in action. For example, he has warned that “the DPRK will use without hesitation all the striking forces in its possession, including nuclear weapons” against South Korea if it uses military force to violate North Korea’s sovereignty. This is a conditional threat of the formula “if you do X, I will do Y,” but it is missing an important aspect: “if you do not do X, I will not do Y.” Nonetheless, there are good reasons to expect that Kim will not resort to nuclear use unless seriously threatened. Despite dropping what has historically been North Korea’s prime foreign policy goal—unifying Korea by force or otherwise—Kim’s ultimate political objective of keeping his regime firmly in power has not changed. Kim’s rational desire to remain in power implies he can be deterred from taking aggressive actions toward the South, which would seriously jeopardize this goal.
It is important to remember that deterrence is not purely a passive policy, even if the choice to attack is ultimately left to the aggressor. Actors cannot simply make deterrence threats and stand by while the potential adversary decides what to do. Deterrence loses potency when it resembles a scarecrow in a cornfield, meant to deter birds merely through its presence. Instead, an active deterrence strategy, like a farmer with his shotgun who patrols the property (sometimes even firing warning shots), is more effective. Deterrence, therefore, requires frequent adjustment, refinement, demonstration, and fine-tuning. Specifically, long-term deterrence strategies—particularly extended deterrence situations—require updates to stated policies, force posture, military exercises, and tailored capabilities. These efforts should all be geared toward sending a clear and credible message about what behavior will not be tolerated and what the consequences of engaging in that behavior will be.
In the case of U.S. nuclear policy in Korea, no major changes are required to send clear and credible messages. U.S. deterrence has an advantage because there is little doubt about U.S. willingness to support South Korea. The formal U.S. commitments and the increased military and political cooperation described above demonstrate that willingness. The continuous U.S. military presence in South Korea for over half a century underscores this commitment. As credibility is key to successful threats, and sunk costs like stationed troops are expected to increase credibility, the United States’ demonstrated willingness to incur costs on behalf of South Korea increases the ease with which leaders can communicate their intentions.
Additionally, the U.S. should not be afraid to be clear it will resort to using nuclear weapons if necessary and should maintain its policy that any North Korean nuclear use would be the end of Kim’s regime. The United States should not be afraid that strong defensive measures and an unshakeable commitment to defend South Korea will provoke Kim to suddenly attack the South. Due to the increased U.S.-ROK military cooperation and the historic political gulf between North and South Korea, Kim recognizes that there is nothing for him to gain through a sudden invasion or attack on South Korea. His primary concern is regime survival, and so an unprovoked attack on the South only puts this at risk. Minor adjustments, however, seem to be in order given new political realities.
These minor adjustments, discussed below, should include: slightly firmer statements that nuclear capabilities would be used, if necessary, in defense of South Korea; more frequent and sustained exercises and military cooperation focused on the defense of South Korea; and firmer commitments to support South Korea’s conventional capabilities, with a focus on missile defense, maritime capabilities, and improved coordination between U.S. and ROK forces. Each of these adjustments contributes to a balance of effectively deterring (and not provoking) the North while also assuring the South.
The foremost adjustment, clearer rhetoric surrounding nuclear weapons, will improve this important balance in two ways. First, it sends an unambiguous signal to North Korea that the United States will not limit itself to conventional responses to a DPRK attack, reducing the likelihood that Kim will feel emboldened behind a shield of nuclear threats. It will also help mollify calls from South Korean audiences for a stronger nuclear commitment. Continuing with the NCG is a concrete way to lend credibility to these assurances.
The second adjustment, more frequent and sustained exercises, will also have a dual-pronged effect, demonstrating credible military responses to the North while providing additional assurance to the South. The annual “Freedom Shield” exercise, scheduled again for 2025 is a prime example.
Third, firmer commitments and support for the South’s own defensive capabilities will similarly cut both ways, demonstrating to the North that the United States will not stand in the way of South Korea’s own defensive measures, and assuring the South that the United States is interested in furthering that growth. This includes continued support for South Korean conventional counterforce capabilities and continued coordination concerning potential nuclear use.
Lastly, amidst the above efforts, the U.S. should engage in sincere and meaningful efforts to improve communication and cooperation between ROK and DPRK military and political entities. This final conciliatory adjustment is perhaps the most important. Kim will not live forever. At some point, the ROK and the United States will face a new generation of leaders who will come of political age in the coming years and decades. In those intervening years, the United States should work toward creating pathways for mutual understanding and crisis management that could eventually ease tensions on the peninsula. The United States must move away from pure hostility to the DPRK (which is rightly seen by Kim as a U.S. desire for regime collapse, failure, or change) and toward a much more tolerant stance. In the current situation, he has no incentive to cooperate. Instead, the United States, alongside the ROK, should sincerely communicate to Kim that if he takes concrete actions to cool tensions on the peninsula and improve humanitarian conditions for his people, the United States will reward those efforts with reduced political hostility. More importantly, the United States and ROK should give this message to anyone in North Korea who will listen. The people of the DPRK, future leaders included, should understand that good behavior will be rewarded, an idea Kim currently dismisses as impossible. The North Korean people must see hope that refraining from aggression could lead to opportunities for prosperity and success.
Conclusion
The United States should be confident that its nuclear policies regarding potential conflict on the Korean Peninsula can work. The United States has an opportunity to reduce tensions on the peninsula while steadfastly supporting an important ally. With the minor adjustments described above, all aimed at clarifying a purely defensive political objective backed by credible threats and assurances, the United States can ensure that Kim continues to have every reason to refrain from a nuclear or large-scale attack on the South. However, the United States should avoid pressure to make drastic policy changes like endorsing a South Korean nuclear weapons program or deploying U.S. nuclear weapons in the region, which would create unwanted escalatory pressures within both the ROK and DPRK. Ultimately, U.S. nuclear policy remains a key element of peace on the peninsula, and the recommendations outlined above would solidify America’s nuclear umbrella as a cornerstone of deterrence.
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Commander Daniel Post, USN, PhD is a professor of Strategy and Policy at the U.S. Naval War College. He received a B.S. in mathematics from the U. S. Naval Academy, an M.A. in national security and strategic studies from the U.S. Naval War College, an M.A. in political science from Brown University, and his Ph.D. in international relations from Brown University. His research focuses on nuclear deterrence, escalation dynamics, limited nuclear war, and conflict termination. He is also the Co-Director of the Perspectives on Modern War Course at the U.S. Naval War College.
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