Rebuilding the Foundations of Offense-Defense Theory

ABSTRACT

The relative ease of attack and defense—the offense-defense balance—is a widely used explanatory concept in international politics, playing an important role in literatures ranging from war causation and alliance formation to the determinants of system structure, the importance of relative gains from cooperation, or the causes of World War I. Yet the concept of the balance itself remains radically underdeveloped theoretically, clouding the predictions of the numerous theories that rest upon it and undermining rigorous empirical work on the many hypotheses these theories imply. I address this problem by presenting and testing a systematic theory of the balance that emphasizes military strategic and tactical choices as its key determinants, by contrast with orthodox offense-defense theory's focus on technology. This new theory outperforms the orthodox view and has broad implications for international relations theory.