While such was the fate of the party in Plataea, the rest of the Thebans who were to have joined them with all their forces before daybreak, in case of anything miscarrying with the body that had entered, received the news of the affair on the road, and pressed forward to their succour. Now Plataea is nearly eight miles from Thebes, and their march delayed by the rain that had fallen in the night, for the river Asopus had risen and was not easy of passage; and so, having to march in the rain, and being hindered in crossing the river, they arrived too late, and found the whole party either slain or captive. When they learned what had happened, they at once formed a design against the Plataeans outside the city. As the attack had been made in time of peace, and was perfectly unexpected, there were of course men and stock in the fields; and the Thebans wished if possible to have some prisoners to exchange against their countrymen in the town, should any chance to have been taken alive. 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; the first messenger having left Plataea just when the Thebans entered it, the second just after their defeat and capture; so there was no later news.
Thus the Athenians sent orders in ignorance of the facts; and the herald on his arrival found the men slain. After this the Athenians marched to Plataea and brought in provisions, and left a garrison in the place, also taking away the women and children and such of the men as were least efficient.
After the affair at Plataea, the treaty had been broken by an overt act, and Athens at once prepared for war, as did also Lacedaemon and her allies. They resolved to send embassies to the King and to such other of the barbarian powers as either party could look to for assistance, and tried to ally themselves with the independent states at home. Lacedaemon, in addition to the existing marine, gave orders to the states that had declared for her in Italy and Sicily to build vessels up to a grand total of five hundred, the quota of each city being determined by its size, and also to provide a specified sum of money. Till these were ready they were to remain neutral and to admit single Athenian ships into their harbours. Athens on her part reviewed her existing confederacy, and sent embassies to the places more immediately round Peloponnese- Corcyra, Cephallenia, Acarnania, and Zacynthus- perceiving that if these could be relied on she could carry the war all round Peloponnese.
And if both sides nourished the boldest hopes and put forth their utmost strength for the war, this was only natural. Zeal is always at its height at the commencement of an undertaking; and on this particular occasion Peloponnese and Athens were both full of young men whose inexperience made them eager to take up arms, while the rest of Hellas stood straining with excitement at the conflict of its leading cities. Everywhere predictions were being recited and oracles being chanted by such persons as collect them, and this not only in the contending cities. Further, some while before this, there was an earthquake at Delos, for the first time in the memory of the Hellenes. This was said and thought to be ominous of the events impending; indeed, nothing of the kind that happened was allowed to pass without remark. The good wishes of men made greatly for the Lacedaemonians, especially as they proclaimed themselves the liberators of Hellas. No private or public effort that could help them in speech or action was omitted; each thinking that the cause suffered wherever he could not himself see to it. So general was the indignation felt against Athens, whether by those who wished to escape from her empire, or were apprehensive of being absorbed by it. Such were the preparations and such the feelings with which the contest opened.