 Wars, Interstate: Patterns and Causes Christian Olsson Université Libre de Bruxelles (ULB) ULB-IEE (CP172/01) 39 Avenue FD Roosevelt 1050 Bruxelles Belgium + 32 472 09 74 34 Christian.Olsson@ulb.ac.be Outline I. Interstate War: From Concept to Patterns 1. The State at War 2. War as Organized Violence 3. Interstateness as Reciprocity and Similarity II. Pathways to War: Causality and Interstate War 1. Explanatory Strategies and Interstate War 2. Causal-Explanatory Approaches to Interstate War in IR 3. Understanding Interstate War: Comprehensive accounts Abstract This article tries to reframe the question of the conceptual unity and sociological diversity of interstate war while highlighting patterns and causes. The challenge is indeed to be able to account for transformation and heterogeneity without falling into the trap of an all- encompassing definition that would make all mutations a priori consistent with its premises. This will done by highlighting how the question of the state, war and the “interstate” sheds light on the contemporary patterns of interstate war (first section). It is only subsequently that this article can raise the question of the causal pathways and motivating factors associated with past and present interstate wars (second section). Keywords Armed conflict, causality, state, international relations, IR theory, historical sociology, interstate system, military, security, territory, violence, war