THE WAR PRONENESS OF ALLIANCES

In the theoretical literature, alliances have been hypothesized to lead to war as well as away from war. This study statistically examines the relationship between the size of alliances and the war proneness of their members. Analyzing data on the war record of 126 major power alliances formed during the period 1816-1980, it is shown that the larger the alliance, the more wars each of its members is likely to be involved in. This result is consistent with, and enhances the credibility of, past empirical research showing that alliance membership affects the expansion of wars rather than their outbreak. This study also explains a puzzle that threatened the validity of past aggregate analyses of the alliance-war relationship: the mysterious reversal of the sign of the relationship around the turn of the twentieth century. The source of the puzzle is demonstrated to have been a failure to think through the theoretical implications of the operationalization of war, not a fundamental change in the nature of the underlying linkage between alliances and war. © 1990, Sage Publications. All rights reserved.