The crisis of Spartan power in the first half of the fourth century has been connected to Spartan inability to manage the hegemony built on the ruins of the Athenian Empire, or interpreted as a result of the unexpected annihilation of the Spartan army by the Boeotians at Leuktra. The present book offers a new perspective, suggesting that the crisis that finally brought down Sparta was in important ways a result of centrifugal impulses within the Peloponnesian League, accompanied by a general awakening of ethnicity in various areas of the Peloponnese. A series of regional case studies is combined with thematic contributions focusing on topics such as the relationship of religious cults and ethnicity and of democracy and ethnicity, the use of archaeological evidence for ethnic phenomena, and comparative approaches based on social anthropology.