Book chapter

Structural Realism/Offensive and Defensive Realism (2010)

in: Oxford Research Encyclopedia of International Studies


Structural realism, or neorealism, is a theory of international relations that says power is the most important factor in international relations. First outlined by Kenneth Waltz in his 1979 book Theory of International Politics, structural realism is subdivided into two factions: offensive realism and defensive realism. Structural realism holds that the nature of the international structure is defined by its ordering principle, anarchy, and by the distribution of capabilities (measured by the number of great powers within the international system). The anarchic ordering principle of the international structure is decentralized, meaning there is no formal central authority. On the one hand, offensive realism seeks power and influence to achieve security through domination and hegemony. On the other hand, defensive realism argues that the anarchical structure of the international system encourages states to maintain moderate and reserved policies to attain security. Defensive realism asserts that aggressive expansion as promoted by offensive realists upsets the tendency of states to conform to the balance of power theory, thereby decreasing the primary objective of the state, which they argue is ensuring its security. While defensive realism does not deny the reality of interstate conflict, nor that incentives for state expansion do exist, it contends that these incentives are sporadic rather than endemic. Defensive realism points towards "structural modifiers" such as the security dilemma and geography, and elite beliefs and perceptions to explain the outbreak of conflict.