Russia has invaded Ukraine. This horrible global crisis raises questions about Putin’s ultimate ambitions, and how nations can make credible deterrent threats in incredible circumstances.

We’re not experts on the Ukraine conflict, but we can dive into the political science research to get some clarity on the underlying dynamics that may be at play. And there’s no better paper to turn to than “Fear, Appeasement, and the Effectiveness of Deterrence” from Alexander V. Hirsch at Caltech.