Nina Tannenwald is Associate Teaching Professor in the Department of Political Science. Her research focuses on the role of international institutions, norms and ideas in global security issues, efforts to control weapons of mass destruction, and human rights and the laws of war. Her book, The Nuclear Taboo: The United States and the Nonuse of Nuclear Weapons Since 1945 (Cambridge University Press, 2007), won the 2009 Lepgold Prize for best book in international relations.   Her current research projects include the future of the nuclear normative order, and compliance with, and effectiveness of, the laws of war. She has co-edited, with Matthew Evangelista, Do the Geneva Conventions Matter? (Oxford, 2017). Her articles have appeared in International Organization, International Security, Journal of Strategic Studies, Ethics and International Affairs, Foreign Affairs, Foreign Policy and the Washington Quarterly, among others. From January-June 2023 she was Fulbright Visiting Professor of International Studies at the Diplomatic Academy in Vienna. She has been a visiting professor at Cornell and Stanford Universities, a Carnegie Scholar, and an MacArthur Foundation Research and Writing Fellow in International Peace and Security. In 2012-2013 she served as a Franklin Fellow in the Bureau of International Security and Nonproliferation in the U.S. State Department. In 2023-2024 she served as Director of Undergraduate Studies in the Political Science Department and in 2019 she completed her second term as Director of the International Relations Program at Brown. She was previously assistant professor at the University of Colorado at Boulder, and Joukowsky Family Assistant Research Professor and then associate research professor at the Watson Institute. She holds a master's degree from the Columbia School of International and Public Affairs and a Ph.D in international relations from Cornell University. In an exclusive interview she answered our questions like the following:

Gulan: Your research has demonstrated how even the most proficient regimes can be constrained by strong norms like the nuclear taboo. What distinguishes a robust international norm from one that is only momentarily successful in a time of great-power competition and norm contestation, and how can we analytically identify the point at which degradation becomes irreversible?

Professor Dr. Nina Tannenwald: These are good questions about how one measures or assesses the strength of a norm. The evidence for a norm lies in institutions and policies that reflect the norm, behavior that is consistent with the norm, and discourse – how people talk about the norm. A robust norm is one that is clearly reflected in behavior, policies and discourse. However, it is often difficult to assess the robustness of a norm at a single point in time. Instead, it is easier to identify change or trendlines over time, e.g. does the norm appear to be strengthening or weakening relative to an earlier period? It may be difficult to identify the point at which degradation becomes irreversible (witness how difficult it is to identify when the erosion of democracy in a given country has become irreversible). And even a norm that has been strongly eroded may still be reversible (the laws of war were eroded by WWII but then were reconstructed in the post-war period). A use of nuclear weapons during war would certainly violate the nuclear taboo, but whether it completely eroded the taboo would depend on how states responded to the violation. They could try to bolster the taboo or they could let it erode.

Gulan: You also demonstrate how inconsistent and situation-specific adherence to the laws of war is. How much do you think real normative internalization, as opposed to strategic calculation, drives compliance now, and is this distinction still important for protecting civilians in modern conflicts?

Professor Dr. Nina Tannenwald: Both internalization and strategic calculation can help to uphold norms. Interestingly, the ICRC does not care which mechanism operates as long as there is behavioral compliance with the norms. Russia’s attacks on civilians and civilian structures in Ukraine (along with its earlier brutal behavior in Syria and Chechnya) are eroding the laws of war.  Perhaps even more damaging is the assault from self-proclaimed democracies. The US and Israel, which claim to have internalized the laws of war in their professional militaries have set aside the laws of war in the Gaza war. This is especially bad for norms.  I would say that Western professional militaries –apart from the US and Israel today—still care about the laws of war in their own behavior, while humanitarian NGOs care generally. But even strategic calculations – Israel’s reputation--do not seem to be sufficient to get Israeli leaders to adhere to the laws of war. In sum, the erosion of both internalization and strategic calculation is bad for the protection of civilians generally. No one is doing much to help the civilians caught in the brutal war in Sudan, for example.

Gulan: The conventional normative architecture of restraint in war is challenged by emerging military technologies like autonomous weapons, cyberwarfare, and AI-enabled targeting. Do you think these technologies will speed up normative adaptation or jeopardize the possibility of shared legal-moral frameworks?

Professor Dr. Nina Tannenwald: Right now, we are way behind in the regulation of new technologies. I see little evidence that they are speeding up normative adaptation; rather, they are more likely to jeopardize existing legal frameworks. Drones, for example, can facilitate precision targeting because they can hover for a long time waiting for the right moment. On the other hand, they can also be used to strike civilian targets and are increasingly being used for strikes far behind the front lines or off the battlefield, which is a violation of the laws of war.

Gulan: Global rivalry is increasingly framed in terms of civilization and norms in the U.S. National Security Strategy. Given that strategic imperatives frequently seem to take precedence over restraint, especially when it comes to China and Russia, how do you evaluate the legitimacy of U.S. normative leadership on weapons limitation and the rules of war?

Professor Dr. Nina Tannenwald: Well, especially in the wake of the US regime change action in Venezuela, I think the US has zero legitimacy on normative leadership of almost any kind. Even if you dislike Maduro and are happy to see him go (as I am) this use of force to kidnap a leader of a sovereign state is a stunning violation of international law. It basically says that the rule of the jungle will prevail. It also opens the door for Russia and China to do the same thing for leaders and regimes that they don’t like.

Gulan: Does the 2025 U.S. security posture strengthen the nuclear taboo, quietly erode it, or change it into a more conditional and instrumental norm in light of discussions about nuclear modernization, extended deterrence, and tactical nuclear weapons?

Professor Dr. Nina Tannenwald: US nuclear modernization has been going on since the Obama administration so the 2025 US nuclear statement is at some level simply an extension of that. The statement doesn’t directly erode the taboo (it doesn’t say anything about the taboo or the 80-year tradition of non-use) but it certainly doesn’t strengthen it. The renewed emphasis on tactical nuclear weapons, which some people see as more “usable” (because they are less destructive), is the development that most challenges the taboo.

Gulan: Strong rhetorical taboos against nuclear use have been reinforced as worries of nuclear escalation have been rekindled by the Russia-Ukraine war. Do you think that by normalizing nuclear threats as instruments of coercion, this war will ultimately erode nuclear restraint or increase it via shared fear?

Professor Dr. Nina Tannenwald: Russia’s war in Ukraine has certainly put nuclear fear back on the agenda. Russia has tried to normalized nuclear threats but the pushback has been reasonably widespread and significant. Nevertheless, the war has likely spurred a greater interest among some countries in acquiring nuclear weapons as the supposed ultimate deterrent. Further, when New START expires in February, the last vestiges of US-Russia bilateral arm control will disappear this year. So, on balance, I think we are seeing an erosion of nuclear restraint.

Gulan: Asymmetry, non-state entities, and highly populated civilian areas are common features of conflicts in the Middle East. Do these conflicts reveal structural flaws in the laws of war that call for normative rethinking rather than just improved enforcement, or are the Geneva Conventions adequately suited to govern such conflicts?

Professor Dr. Nina Tannenwald: The Geneva Conventions were written for wars between states and do less well for conflicts when states are fighting non-state actors or highly asymmetric wars. I don’t think they need fundamental normative rethinking – protection of civilians and prisoners of war continues to be normatively right and desirable. However, clarifying how to apply them in highly urban wars with non-state actors, and in the era of AI targeting, remains an ongoing task.  There’s no way to get around the fact that regulating war is a tough challenge, especially when it is being fought for ideological goals.

Gulan: Do you see nuclear restraint relying on taboo-like moral prohibition in the future, or are we heading toward a more precarious order based on managed risk, deterrence bargaining, and conditional acceptability of nuclear use? If so, how might this change affect the likelihood of averting nuclear war?

Professor Dr. Nina Tannenwald: It’s not either/or. For now, the taboo continues to be widely held, even as the nuclear arms race proceeds. I don’t see a “conditional acceptability of nuclear use” emerging right now – nuclear-armed governments continue to view nuclear use as a last resort, even as they engage in nuclear arms build-ups and riskier deterrence behavior. The most likely scenario for nuclear use is not a bolt-out-of-the blue strike but rather as a result of misperception or miscalculation in a crisis. There is, on balance, less nuclear restraint now, and more nuclear excess, and that increases the risk of nuclear war.