History of the Peloponnesian War

After these things, though not many years later, what we have before narrated now took place, namely, the affair of Corcyra, and that of Potidaea, and whatever was made a pretext for this war.

All these things that the Greeks performed against one another and the barbarian, occurred in about fifty years, between the retreat of Xerxes and the beginning of this war: in the course of which the Athenians established their empire on a firmer footing, and themselves advanced to a great pitch of power; while the Lacedaemonians, though they perceived it, did not try to stop them, except for a short time, but remained quiet the greater part of the period. For even before this they were not quick in proceeding to hostilities, unless they were compelled; and to a certain extent also they were hindered by intestine wars; [*]( He seems to refer especially to the revolt of the Helots.) until the power of the Athenians was clearly rising to a dangerous height, and they were encroaching on their confederacy. Then, however, they considered it no longer endurable, but were of opinion that they ought with the greatest resolution to attack their power, and overthrow it, if they could, by commencing this war. Now the Lacedaemonians themselves had decided that the treaty had been broken, and that the Athenians were guilty;

but they sent to Delphi and inquired of the god, whether it would be better for them if they went to war : and he answered them, as it is reported, that if they carried on the war with all their might, they would gain the victory; and said that he would himself take part with them, whether called upon or not.