Early Helladic period (XXX - XXI centuries BC)

In the early Helladic period, the territory of mainland Greece was inhabited by a population called Pelasgians in the late ancient tradition. Most likely, in terms of ethnic composition, it was not Indo-European, but pre-Greek.

At the end of this period, fortified settlements appear in some coastal areas. The earliest was a typical tribal village near the modern town of Rafina in Attica. It had streets paved with stone, along which rectangular houses were built. There were also metallurgical workshops in the village, indicating the development of metal foundry. Another type of settlements is presented in the town of Lerna (Peloponnese, Argolis region) - this is a fortified citadel. Palace buildings were found here, built of fragile raw brick, with walls up to one meter thick. They had two floors: the lower tiers were warehouses, and the upper ones served as front rooms where people lived. The roofs of the houses were covered with tiles. There was a small settlement around the palace.

At the turn of the 3rd-2nd millennia, a major event occurs in Greece when it is inhabited by aliens (approximately from the 21st-20th centuries BC). From the north, from the Danube lowlands or from Thessaly, come tribes later called Achaeans. The local population is leaving habitable places, such as near Rafina or in Lerna, which the aliens could destroy. The later idea of ​​the disappearance of the settlement in Lerna is probably associated with the second feat of Hercules, who defeated the terrible monster - the Lernean hydra. He cut off the head of the hydra, and smeared it with arrows with poison, from which he later died. The murder of the monster could reflect the wars waged by the Achaeans with the local population.

The tribes that came, partly destroyed the Pelasgians, and partly assimilated them, were definitely Greeks and the immediate predecessors of the Greek ethnos of the 1st millennium. It is possible that assimilation proceeded gradually, without a sharp expansion, when the Achaeans gradually penetrated into Greece.