Summary

A large body of theoretical work posits that power shifts or expected power shifts cause war. Power transition theory, cyclic theories of war, preventive war arguments, and the bargaining model of war are discussed in this article. Indeed, shifting power is one of the most popular and venerable explanations for war. Its origins go at least as far back as Thucydides, who famously wrote, “What made war inevitable was the growth of Athenian power and the fear this caused in Sparta.” Two major points must be discussed. First, there is an impressive correlation between major power war and shifting power, a correlation consistent with the arguments of several systemic theories of war. Second, much of the empirical research examining power shifts and war suffers from endogeneity and model specification concerns. Regarding endogeneity, more effort should be placed on identifying valid instruments and conducting experiments. Regarding model specification, more attention needs to be paid to scope conditions. Shifting power is not expected to cause war in all contexts. Precisely defining the relevant contexts and modeling them empirically is necessary to evaluate the shifting power and war hypothesis.