History of the Peloponnesian War
Thucydides
Thucydides, Vol. 1-4. Smith, Charles Foster, translator. London and Cambridge, MA: Heinemann and Harvard University Press, 1919-1923.
and on the ground that they had not received fair treatment went over to the Argives, their envoys making the alliance as they had been instructed to do. Immediately after them the Corinthians also and the Chalcidians in Thrace became allies of the Argives. But the Boeotians and Megarians, though holding the same views, kept quiet, awaiting events and thinking the Argive democracy not so advantageous for them, with their oligarchical form of government, as the political constitution of the Lacedaemonians.
About the same time during this summer, the Athenians reduced the Scionaeans by siege, slew the adult males,[*](In accordance with the decree moved by Cleon two years before (4.122.6). At the conclusion of peace they had been left at the mercy of the Athenians (5.18.8).) made slaves of the women and children, and gave the land to the Plataeans to occupy; and they brought back the Delians to Delos,[*](cf. ch. i.) taking to heart their mishaps in the battles[*](At Delium and Amphipolis.) and obeying an oracle of the god at Delphi.
Meanwhile the Phocians and the Locrians began hostilities.
And the Corinthians and the Argives, being now allies, came to Tegea,[*](It had always maintained an independent position in Arcadia, and in earlier times had been a powerful opponent Of Sparta.) hoping to induce it to revolt from the Lacedaemonians, seeing that it was an important part of the Peloponnesus, and thinking if it should be gained to their side they would soon have the whole Peloponnesus.
But when the Tegeates refused to oppose the Lacedaemonians, the Corinthians, who up to that time had been working zealously, became slack in their ardour and full of dread that none of the other Peloponnesians would henceforth come over to them.