History of the Peloponnesian War

As for the Athenians, while the colonists were being gathered for this city, they at first became alarmed, thinking it was being established chiefly as a menace to Euboea, because it is only a short distance across from here to Cenaeum in Euboea. Afterwards, however, the matter turned out contrary to their expectations; for no harm came from the city.

And the reasons were as follows: the Thessalians, who were the paramount power in those regions and whose territory was being menaced by the settlement, fearing that their new neighbours might become very powerful, began to harry and make war continually upon the new settlers, until they finally wore them out, although they had at first been very numerous; for, since the Lacedaemonians were founding the colony, everybody came boldly, thinking the city secure. One of the principal causes, however, was that the governors sent out by the Lacedaemonians themselves ruined the undertaking and reduced the population to a handful, frightening most of the settlers away by their harsh and sometimes unjust administration, so that at length their neighbours more easily prevailed over them.