History of the Peloponnesian War

For it is plain that what is now called Hellas was not of old settled with fixed habitations, but that migrations were frequent in former times, each tribe readily leaving its own land whenever they were forced to do so by any people that was more numerous.

For there was no mercantile traffic and the people did not mingle with one another without fear, either on land or by sea, and they each tilled their own land only enough to obtain a livelihood from it, having no surplus of wealth and not planting orchards, since it was uncertain, especially as they were yet without walls, when some invader might come and despoil them. And so, thinking that they could obtain anywhere the sustenance required for their daily needs, they found it easy to change their abodes, and for this reason were not strong as regards either the size of their cities or their resources in general.

And it was always the best of the land that was most subject to these changes of inhabitants—the districts now called Thessaly and Boeotia, most of the Peloponnesus except Arcadia, and the most fertile regions in the rest of Hellas.

For the greater power that accrued to some communities on account of the fertility of their land occasioned internal quarrels whereby they were ruined, and at the same time these were more exposed to plots from outside tribes.

Attica, at any rate, was free from internal quarrels from the earliest times by reason of the thinness of its soil, and therefore was inhabited by the same people always.

And here is an excellent illustration of the truth of my statement that it was owing to these migrations that the other parts of Hellas did not increase in the same way as Attica; for the most influential men of the other parts of Hellas, when they were driven out of their own countries by war or sedition, resorted to Athens as being a firmly settled community, and, becoming citizens, from the very earliest times made the city still greater in the number of its inhabitants; so that Attica proved too small to hold them, and therefore the Athenians eventually sent out colonies even to Ionia.