History of the Peloponnesian War
Thucydides
Thucydides. History of the Peloponnesian War. Crawley, Richard, translator. London and Toronto: J. M. Dent and Sons Ltd.; New York: E. P. Dutton and Co., 1914.
Such was their plan. But the Plataeans suspected their intention almost before it was formed, and becoming alarmed for their fellow-citizens outside the town, sent a herald to the Thebans, reproaching them for their unscrupulous attempt to seize their city in time of peace, and warning them against any outrage on those outside. Should the warning be disregarded, they threatened to put to death the men they had in their hands, but added that, on the Thebans retiring from their territory, they would surrender the prisoners to their friends.
This is the Theban account of the matter, and they say that they had an oath given them. The Plataeans, on the other hand, do not admit any promise of an immediate surrender, but make it contingent upon subsequent negotiation: the oath they deny altogether.
Be this as it may, upon the Thebans retiring from their territory without committing any injury, the Plataeans hastily got in whatever they had in the country and immediately put the men to death. The prisoners were a hundred and eighty in number; Eurymachus, the person with whom the traitors had negotiated, being one.
This done, the Plataeans sent a messenger to Athens, gave back the dead to the Thebans under a truce, and arranged things in the city as seemed best to meet the present emergency.
The Athenians meanwhile, having had word of the affair sent them immediately after its occurrence, had instantly seized all the Boeotians in Attica, and sent a herald to the Plataeans to forbid their proceeding to extremities with their Theban prisoners without instructions from Athens. The news of the men's death had of course not arrived;