In the heroic age Peloponnesus was occupied by tribes of Dorian conquerors. They had no share in the glories of the Heroic age; their name does not occur in the Iliad, and they are only once mentioned in the Odyssey; but they were destined to form in historical times one of the most important elements of the Greek nation. Issuing from their mountain district between Thessaly, Locris and Phocis, they overran the greater part of Peloponnesus, destroyed the ancient Achaean monarchies and expelled or reduced to subjection the original inhabitants of the land, of which they became the undisputed masters. This brief statement contains all that we know for certain respecting this celebrated event, which the ancient writers placed eighty years after the Trojan war (B.C. 1104). The legendary account of the conquest of Peloponnesus ran as follows: - The Dorians were led by the Heraclidae, or descendants of the mighty hero Hercules. Hence this migration is called the Return of the Heraclidae. The children of Hercules had long been fugitives upon the face of the earth. They had made many attempts to regain possession of the dominions in the Peloponnesus, of which their great sire had been deprived by Eurystheus, but hitherto without success. In their last attempt Hyllus, the son of Hercules, had perished in single combat with Echemus of Tegea; and the Heraclidae had become bound by a solemn compact to renounce their enterprise for a hundred years. This period had now expired; and the great-grandsons of Hyllus - Temenus, Cresphontes, and Aristodemus - resolved to make a fresh attempt to recover their birthright. They were assisted in the enterprise by the Dorians. This people espoused their cause in consequence of the aid which Hercules himself had rendered to the Dorian king, AEgimius, when the latter was hard pressed in a contest with the Lapithae. The invaders were warned by an oracle not to enter Peloponnesus by the Isthmus of Corinth, but across the mouth of the Corinthian gulf. The inhabitants of the northern coast of the gulf were favourable to their enterprise. Oxylus, king of the AEtolians, became their guide; and from Naupactus they crossed over to Peloponnesus. A single battle decided the contest. Tisamenus, the son of Orestes, was defeated and retired with a portion of his Achaean subjects to the northern coast of Peloponnesus, then occupied by the Ionians. He expelled the Ionians, and took possession of the country, which continued henceforth to be inhabited by the Achaeans, and to be called after them. The Ionians withdrew to Attica, and the greater part of them afterwards emigrated to Asia Minor.

The Heraclidae and the Dorians now divided between them the dominions of Tisamenus and of the other Achaean princes. The kingdom of Elis was given to Oxylus as a recompense for his services as their guide; and it was agreed that Temenus, Cresphontes, and Eurysthenes and Procles, the infant sons of Aristodemus (who had died at Naupactus), should draw lots for Argos, Sparta, and Messenia. Argos fell to Temenus, Sparta to Eurysthenes and Procles, and Messenia to Cresphontes.

Such are the main features of the legend of the Return of the Heraclidae. In order to make the story more striking and impressive, it compresses into a single epoch events which probably occupied several generations. It is in itself improbable that the brave Achaeans quietly submitted to the Dorian invaders after a momentary struggle. We have, moreover, many indications that such was not the fact, and that it was only gradually and after a long protracted contest that the Dorians became undisputed masters of the greater part of Peloponnesus.