The Lelantine War, one of the earliest conflicts in ancient Greek history attested by sources, was fought on Euboea between Chalcis and Eretria – the two most prominent centers of the Greek world in the 8th century BC. Several other Greek states participated in the conflict at various stages as allies of one side or the other. This article highlights two key observations. First, it reconstructs the specific causes of the war in connection with Eretria’s relocation to a new site.