Abstract: Has the shift in Washington's approach toward U.S. allies undermined NATO’s credibility? To address this critical question, we conducted a large, survey-based longitudinal study investigating changes in perceptions of NATO’s collective defense commitments across selected allied states (the United States, the United Kingdom, Germany, Poland, and Canada), the Russian Federation, and in the British and German parliaments. In line with our theory of retrenchment signaling, we found a dramatic decline in the credibility of the U.S. commitments to NATO during the first year of Trump’s second administration (first-order effect), accompanied by a more modest increase in the credibility of non-U.S. allies (second-order effect). We demonstrate that the net impact on NATO’s overall credibility has been negative, showing asymmetric alliances suffer from a “substitution deficit” in credibility signaling. Furthermore, our investigation in Russia suggests that U.S. retrenchment signaling has even more negative consequences for allied deterrence than assurance due to the “strongest-link bias,” in which adversaries tend to overidentify the credibility of asymmetric alliances with that of their leading power. Finally, we show that political elites across allied states have been at least as skeptical about the U.S. commitment to defend its allies as the general population. Our longitudinal study provides the first systematic empirical evidence of the erosion of NATO’s credibility under “Trump 2.0” and contributes to scholarship on the dynamics of military alliances and the impact of great power retrenchment on world politics.
Dr. Lauren Sukin is the John G. Winant Associate Professor in US Foreign Policy in the Department of Politics and International Relations at the University of Oxford, as well as a Professorial Fellow in Nuffield College at the University of Oxford. Dr Sukin's research examines historical and contemporary challenges in international security, focusing particularly on the role of technology—including nuclear weapons—in alliances. Dr Sukin's research explores military strategy, deterrence and reassurance, and alliance challenges in Europe and East Asia. Her work has been published in a variety journal and press outlets including Security Studies, Journal of Conflict Resolution, Journal of Peace Research, International Studies Quarterly, Foreign Policy, and Foreign Affairs, among others. Dr Sukin is an Affiliate at Stanford University's Center for International Security and Cooperation (CISAC), a Nonresident Scholar in the Nuclear Policy Program at the Carnegie Endowment for International Peace, and a Fellow at Charles University's Peace Research Centre Prague. She holds a PhD and MA from the Department of Political Science at Stanford University and ABs in political science and literary arts from Brown University.
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