The Concentration of Capabilities and the Onset of War

Recent empirical research has produced no consensus on what (if any) relationship exists between the concentration of capabilities and the onset of war. The results of this article indicate that concentration is related to the frequency of war, but that rather than the monotonic relationship predicted by both balance of power and power preponderance theories, the relationship appears to have an inverted U-shape. We also show that concentration can be disaggregated into: (1) the number of major powers, and (2) the inequality of capabilities among the major powers. Our analysis shows that both components influence war, but that the effect on war of each component of concentration depends on the level of the other.