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Dilemmas of Deterrence

History reminds us that some factors, like credibility, are crucial to the success of countries’ efforts to prevent undesirable behavior by others. But studying the limits of these efforts is equally important for identifying a strategy that works.

CAMBRIDGE – We live in a world where geopolitical stability relies largely on deterrence. But how can we prove that deterrence works?

Consider the ongoing war in Europe. Beginning in December 2021, US President Joe Biden warned Russian President Vladimir Putin that Russia would face severe new sanctions if he invaded Ukraine, to no avail. Then, when the United States and its European allies thwarted Russia’s plans by providing arms to Ukraine, Putin brandished the nuclear option. But Western aid continued unabated.

Did deterrence fail or succeed? Answering this question poses a challenge because it requires assessing what would have occurred absent the threat. It is hard to prove a negative. If I put a sign on my front door saying, “No Elephants,” and there are no elephants in my house, did I deter them? It depends on the likelihood of literate elephants entering in the first place.

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