ABSTRACT
This chapter introduces the concepts and theories employed in understanding the causes of war and the changing nature of global violence. It examines how unit-level and system-level factors such as regime type and polarity can create conditions conducive to war or peace. Although interstate war is in decline, military force a key element of power remains an attractive alternative. Individual-level explanations provide insights into the passions of ordinary citizens and leaders' motives in violent intrastate conflicts such as the Rwanda genocide and ethnic cleansing in Bosnia and Kosovo. The chapter also examines theories regarding the causes of interstate wars. Power-sharing arrangements, may not be sufficient to resolve conflicts, and may create conditions for future wars. Realists regard war as the most important fact of global politics. Rapid change in the distribution of capabilities among actors has long been cited as a cause of war.
