Structural realism

Structural realism, or neorealism, as introduced by Kenneth Waltz (1979), is a strand as realism that explains international politics based on the structure of the international system. For Waltz, the structure of the system corresponds with the number of great powers with their respective capabilities. Hence, the international structure can be multipolar (like in the 19th century, with Britain, Russia, France, Austria(-Hungary) and Prussia/Germany), bipolar (like during the Cold War, with the US and Soviet Union) or unipolar (like right after the Cold War, when, according to some, the structure was dominated by the US as single remaining great power).

Structural realism is a 'systems theory', as it assumes that the whole of the system (i.e. the anarchical international system with a certain structure) is more than the sum of the parts (i.e. the states). In other words, they situate explanation at the level of the structure, beyond the specific characters and interactions of the states. Put differenty, structural realists prioritze the international system as level of analysis.

Competition, conflict and war are largely to be explained by the anarchical nature of the international system, i.e. the absence of any authority above the states that maintains peace. Despite all their differences in terms of regime type, ideology, etc., structural realists consider states as 'like-units', because they all share the basic interest of survival. In the context of anarchy, great powers and other states have to rely on themselves for security. In this 'self-help' regime, states must build up their armaments and/or form smart alliances themselves. But by doing so, they fuel security dilemmas among each other, which can lead to war.

Waltz and other structural realists acknowledge that their theory cannot explain particular international event and developments such as conflicts and wars. It is not a theory of the foreign policy of states and their relations with others. Therefore, their theory is complementary to foreign policy analysis and other theoretical strands.

An interesting distinction within structural realism is the one between 'defensive' and 'offensive realism.'