The multiple hierarchy model requires extensive attention to case definition and variable measurement. I need information about a number of important variables in order to evaluate the model's hypothesis that power parity and dissatisfaction with the relevant status quo increase the probability of war within international hierarchies. In addition to knowing when wars occur or do not occur I need to know what a local hierarchy is, when contenders in such hierarchies are at parity, and whether the challenger is dissatisfied with the status quo. In sum, the evaluation of the hypothesis necessitates operational definitions of local hierarchies as well as of the variables highlighted by the model. Local hierarchies are not a self-evident phenomenon. What it means to be at parity, and even more, what it means to be a dissatisfied actor, are similarly non-obvious. Nevertheless, these are the theoretically important concepts in my analysis, and as such must be operationally defined. In order to clarify the operational definitions I offer, I go to some length justifying my choices and explaining my rationales. I subject my readers to all this detail in an effort to make my procedures as transparent as possible, and thus replicable and, ideally, amenable to subsequent improvement.

Constructing operational definitions of these concepts allows me to evaluate the multiple hierarchy model's central hypothesis about when wars will and will not occur within international hierarchies. However, these concepts are increasingly important to other explanatory efforts in world politics research.