Measuring Systemic Polarity

Indicators of the tightness and discreteness of poles in the international system, as well as of the distribution of capabilities and interaction opportunities among poles, are developed. With alliance bonds as the focus, scores for each indicator are presented for each year of the past century and a half, and several prevalent theories linking polarity to war are tested. The amount of major power war begun during five-year periods is found to be unrelated to the tightness of the poles, although increases in tightness are substantially associated with large amounts of war. Bipolar systems are found to experience less war than multipolar systems, with increases in the number of clusters being especially strongly associated with the amount of major power war during subsequent five-year periods. Neither changes in the discreteness nor the distribution of capabilities among the poles has any appreciable effect on the amount of major power war.