Polarity, balances of power and war: Explaining some puzzling correlates of war project results

Empirical evidence has not stopped arguments about the relative peacefulness of multipolar versus bipolar systems of states and whether parity, not preponderance of power, encourages interstate war. Two basic studies of war and peace since 1815 find “radical differences” depending on the century. Singer and Small (1968) report that “alliance aggregation and bipolarity predict strongly away from war in the nineteenth century and even more strongly toward it in the twentieth.” Singer, Bremer, and Stuckey (1972) found preponderance associated with peace in the twentieth century and with war in the nineteenth century. These apparent inconsistencies are remarked upon far more often than they are examined. Re‐analyses indicate that any differences are not as stark as originally made out to be. There is no evidence in these studies that those who acted for states acted differently depending upon the century. Hence explanations as to why states did act differently are misguided.