The Idea of a Balance of Power

In this course, we will examine the idea of a balance of power—one of the key terms in the disciplines of international relations, strategic theory, and history—and also some instances in diplomatic and military history that will allow us to assess some versions of the theory. In its purest and most optimistic version, a balance of power is imagined to be a self-adjusting system of military alliances, one in which a balance of power keeps the peace by preventing any one state from accumulating so great a relative military advantage that war may seem a rational course of action. In a slightly less optimistic form, a balance of power can mean a distribution of power among states sufficient to prevent any one major power from seriously threatening the fundamental interests of another. In significantly less optimistic versions, the pursuit of a balance of power is imagined to be as likely to provoke wars as to prevent them, and a very equal balance of power may simply insure that a war will be peculiarly protracted and destructive. The First World War is sometimes imagined to be a war both caused and protracted by balance-of-power policies, while the Second World War is often imagined as the horrific result of insufficient attention to the maintenance of a dissuasive balance of power. The phrase dates to at least 1701, was memorably expressed in an essay of Hume’s (Of the Balance of Power) in 1752, is clearly imagined to exert pressure on political actors as early as Thucydides’ The Peloponnesian War, and is sometimes considered one of the core theories of international relations. We shall look at different versions of the theory and at some of the history that the theories attempt to explain, particularly the outbreak and prevention of wars, some sequences of diplomatic history, and arms races.