The Shadow of Deterrence: Why Capable Actors Engage in Contests Short of War

Defense policy makers have become increasingly concerned about conflict in the “gray zone†between peace and war. Such conflicts are often interpreted as cases of deterrence failures, as new technologies or tactics—from cyber operations to “little green men†—seem to increase the effectiveness of low-intensity aggression. However, gray zone conflict could also be a case of deterrence success, where challengers adopt a constrained form of aggression in response to a credible escalation threat. We develop a model that formalizes both scenarios and identifies distinct empirical patterns across the two cases. We use the model’s findings to empirically analyze Russian gray zone activity since the 1990s, finding that Russian activity appears, in part, to be restrained by NATO’s deterrent threat. Our model also shows that developing gray zone conflict capabilities can lead to more peace but could also backfire and provoke a challenger to escalate to war.