Rivalry is pervasive in many areas of life. Though rivalry is not isolated to international politics, interstate rivalries are particularly important given their conflict propensities and destructiveness. Tremendous progress has been made in determining the causes of rivalry initiation, maintenance, escalation, and termination. What we know empirically about rivalry, however, hinges on how the concept of rivalry is defined and which dyads are identified as rivals for which periods of time. Though the what, who, and when questions of rivalry may seem straightforward and the answers to such questions in some cases obvious, defining and identifying rivals has not been without scholarly controversy.
There are several approaches to conceptualizing and operationalizing rivalry. Each approach has strengths and weaknesses. Dispute density approaches, for example, which identify rivals as states that engage in repeated instances of militarized conflict over time, have higher levels of measurement reliability than validity. The strategic rivalry approach, on the other hand, which identifies rivals as states that view one another as threatening competitors and enemies, has a higher level of measurement validity than reliability. Rather than advocating one approach over another, the intent of this article is to lay bare the strengths and weaknesses of different ways of identifying cases of rivalry.
Existing rivalry research provides a foundation from which to further develop rivalry approaches. Given that the concept of rivalry has only recently been applied outside of the dyadic interstate context, additive research is still needed on rivalry in intrastate, triadic and multistate, and other settings. Due to the existence of several mature dyadic interstate rivalry approaches, on the other hand, developing additional distinct approaches for the dyadic interstate context is less imperative than integrating existing approaches. There are several ways this can potentially be done, such as by combining elements of multiple perspectives in ways that minimize weaknesses, through conceptual mapping, or by developing an ordinal measure of rivalry.