Guest post by Kyungwon Suh
Do nuclear weapons make their possessors more aggressive? A series of high-profile aggressive actions by some nuclear-armed states appear to substantiate the argument that nuclear weapons enable aggressive behavior. Since its all-out invasion of Ukraine in February, Russia has continued to conduct brutal, coercive operations, including missile strikes against Ukrainian civilian infrastructure and population centers. North Korea has continued to test launch a wide array of missiles, one of which recently landed close to South Korea’s territorial waters. Policymakers also echo the view that nuclear weapons are more than simply defensive weapons. The 2022 Nuclear Posture Review argues that Russian leaders have exploited their nuclear arsenal as a “shield” behind which they launched military aggression against Ukraine. When he was CIA Director, Formal Secretary of State Mike Pompeo argued that Pyongyang could use nuclear weapons “beyond self-preservation.”
If the argument that nuclear weapons promote aggression is correct, then it has significant implications for the international order. Specifically, allowing new members to join the nuclear club—like Iran, for example—could do real damage to regional and international security. One could therefore argue that Washington should use every available means to prevent Iran from acquiring nuclear weapons, as Iranian nuclear weapons could be a powerful source of Teheran’s revisionist behavior in the future. Similarly, although momentum is growing to accept a nuclear-armed North Korea, a counterargument can be made that the United States should persist with denuclearization because a nuclear-armed North Korea would pose significant threats to its neighbors and regional peace.
Scholars are divided, however, as to whether nuclear weapons actually encourage states to act belligerently because evidence from research on nuclear weapons is mixed. For example, research on the cases of South Africa and Pakistan, as well as quantitative data analysis, suggests that nuclear weapons can fuel military aggression. Others disagree, however, claiming that there is no strong evidence that nuclear-armed states tend to act more aggressively.
In my Journal of Conflict Research article, I revisited quantitative evidence on whether possessing nuclear weapons emboldens governments to be more aggressive. I focused on one key type of aggressive behavior: the initiation of militarized disputes between states by threatening, displaying, or using force. My analysis revealed two key patterns. First, on average, nuclear-armed states are no more likely than non-nuclear states to initiate military conflicts against other states. Second, instead of fueling conflict, nuclear weapons deter conflict. States that have nuclear weapons are less likely than non-nuclear states to be involved in militarized disputes—whether their opponent has nuclear weapons or not.
If nuclear weapons do not encourage military aggression, how can they deter conflict? After all, the idea that having nuclear weapons enables states to shield themselves from retaliation for their aggressive behavior depends on the assumption that they would actually use those nuclear weapons if they meet resistance. One possibility is that threats of nuclear escalation for defensive goals may be seen as more credible than offensive aims. For instance, defending one’s territorial integrity from military encroachment is perceived as more legitimate than using force to seize territory from another state. This could lend credibility to threats of nuclear retaliation by defenders. Absent such an advantage, initiators of military actions can credibly threaten nuclear escalation only if there are other facilitating conditions, such as strong territorial irredentism.
Moreover, there are multiple drivers of states’ aggressive foreign policy behavior other than nuclear weapons. For instance, experts argue that personalist leaders, such as Vladimir Putin, are often more willing to accept risk to achieve their goals, which could explain Russia’s invasion and its risky actions. It is also possible that North Korea’s recent military provocation is a part of its tendency to engage in military actions around US elections, a pattern that existed before Pyongyang acquired nuclear weapons. In other words, countries’ belligerent actions are likely to have multiple causes, and it is premature to conclude that nuclear weapons are either a sole determinant or that their influence overrides other considerations.
Of course, nuclear weapons may embolden states in some cases, and living with nuclear-armed states is not a risk-free business. However, the dangers of nuclear weapons emboldening dangerous regimes may not be as significant as is often believed. Therefore, overestimating the emboldening power of nuclear weapons may become a self-fulfilling prophecy. By exaggerating the potential dangers posed by nuclear-armed states, Washington may set unreasonably high demands during bargaining with Iran or may pursue unrealistic goals, such as the complete denuclearization of North Korea. This could reduce the chance of achieving imperfect but meaningful political settlements and increase the odds of conflict by fostering mistrust between the United States and its rivals. An evidence-based, sober assessment of the risks posed by nuclear weapons in the hands of adversaries is an important first step towards crafting workable foreign policies toward nuclear-armed rivals and sound approaches to nuclear non-proliferation.
Kyungwon Suh is a Postdoctoral Fellow in International Security and Technology at the UC Institute on Global Conflict and Cooperation.