An “arms race” is a competition over the quality or quantity of military capabilities between states in the international system. The arms race phenomenon has received considerable attention from scholars over many decades because of the ubiquity, throughout history, of states building arms as a means of deterring enemies, but disagreement persists over whether that policy is effective at avoiding war.
The Latin phrase si vis pacem, para bellum, meaning “if you want peace, prepare for war,” dates back to the Roman Empire but the sentiment is likely much older. That states should rapidly build up their militaries in the face of potential threats is a common thread that runs through much of the modern international relations scholarship influenced by realism and deterrence theory. Meeting force with force, the logic went, was the only way to ensure the security or survival of the sovereign state. These states faced a paradox, however, best articulated by the “security dilemma.” Anything a state does in the name of defense, like a rapid military buildup, decreases the security of other states and will be viewed with hostile intent. This set up a debate over competing expectations regarding the relationship between arms races and war (peace). On one hand, deterrence theory posits that rapid arming is necessary to raise the cost of an adversary attacking and, consequently, preserves peace. On the other hand, the spiral model argues that the reality of the security dilemma means that arming produces mistrust, hostility and, thus, increases the likelihood of war. Scholars set out to test these competing hypotheses using large data sets and statistical techniques, but there was widespread disagreement on how to measure arms races, appropriate research design, and the statistical findings were somewhat mixed.
Critics of this approach to studying arms races note a number of important weaknesses. First, scholars primarily focus on the consequences of arms races—whether they lead to war or peace—at the expense of understanding the causes. Those who advance this position believe that a theory of arms race onset might well inform our understanding of their consequences. Second, security dilemma, taken as the primary motivation for arms races, suffers from significant logical flaws. Third, assessment of the arms race-war relationship consists of comparative theory tests of deterrence theory and spiral model, yet these ideas are underdeveloped and expectations oversimplified. More recently, scholarship has shifted the focus from the consequences of arms races to developing theories and empirical tests of their causes. These efforts have been informed by insights from bargaining models of war, and their application to this context holds promise for better future understanding of both the causes and consequences of arms races.