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.
These very Athenians, for example, when the Persians contrary to expectation signally failed, grew great on the repute that it was Athens they went against; so in our case a like issue is not beyond hope.
"With confidence, then, let us make our preparations here, but also send envoys to the Sicels, to confirm the allegiance of some and to endeavour to make friendship and alliance with others; and let us despatch envoys to the rest of Sicily, to show that the danger is a common one, and to Italy, that we may either secure their alliance for ourselves or else prevent their receiving the Athenians.
And to me it seems best to send also to Carthage. For the Carthaginians are not without expectation, or rather they are always in fear, that some time the Athenians may come against their city; and so they will probably feel that if they shall leave things here to their fate, they may be in trouble themselves, and therefore will be inclined to assist us, secretly perhaps, or openly, or by some means or other. And they, of all men of the present day, are the most able to do so, if they will; for they have an abundance of gold and silver, by which war and everything else is expedited.
And let us send also to Lacedaemon and to Corinth, begging them to bring aid here with all speed, and to stir up the war over there.