The Dorian invasion is an ancient Greek myth and discredited archaeological hypothesis describing the movement of the Dorian people into the Peloponnese region of Greece. According to the myth, the Dorians migrated from central Greece shortly after the Trojan War and populated most of the southern Peloponnese, particularly the regions of Laconia, Messenia and the Argolid. The myth became combined with that of the Return of the Heracleidae, such that the descendants of the hero Heracles were imagined to have led the Dorians and founded the ruling lines of several Dorian cities, including Sparta. The myth probably emerged during the Early Iron Age as part of a process of ethnogenesis between cities claiming Dorian ancestry. In the fifth century BCE, it gained greater prominence through its use to promote unity among Sparta's Peloponnesian allies, and to differentiate Sparta from its rival Athens, believed to be of Ionian heritage.