Although many countries have ethnic kin on the “wrong side” of their borders, relatively few seek to annex foreign territories on the basis of ethnicity. This article examines why some states pursue irredentism, whereas others exhibit restraint. Most case studies have focused on a handful of prominent cases and advance case-specific explanations that do not generalize well, whereas quantitative studies have almost exclusively emphasized the demand for irredentism. This paper recalibrates the literature toward the supply side by focusing on the interaction of the irredentist state with the co-ethnic enclave and the host state, remedies the selection issue by providing new data on all actual and potential irredentist cases around the world from 1946 to 2014, and provides the first systematic testing of rival explanations within a unified framework.
