Balance of Power, System Polarity and Irredentism

When and where are kin-states more likely to engage in militarized territorial expansion against a kin-group's state of residence, i.e., irredentism, rather than merely employing irredentist rhetoric or engaging in non-irredentist kin-state politics that focus on nurturing cultural ties with co-ethnics abroad? For example, Why did Russia pursue an irredentist policy and annex Crimea but a non-irredentist one toward Narva? Why pursue the annexation of Crimea in 2014 but not in the 1990s or the early 2000s? Various valuable domestic explanations have been proposed, including diversionary war theory, shifts in regime type, and socioeconomic changes; but none has centered on balance of power considerations. I emphasize the role of two variables, whether the kin-group’s state of residence is within or outside the core alliance network of a particular pole and the polarity of the international system at any given point in time, operationalized through the number of poles in the system (one, two, or many). I contend that kin-states are unlikely to target any state of residence that is affiliated with the core alliance network of a pole. Furthermore, I argue that variations in polarity shape the nature and location of irredentism. In a bipolar system, irredentism is likely to take the form of proxy warfare outside each bloc. In a unipolar system, irredentism is more likely in areas where the hegemon exercises the least influence—such as areas linked to a former pole. Finally, in a multipolar system, irredentism is more likely to be pursued by rising powers against neighbors not affiliated with alliance networks of a pole in the international system. I evaluate my argument using an existing dataset of both actual and potential irredentist cases from 1946 to 2014, supplemented by illustrative case studies.