History of the Peloponnesian War

When they had done this, they sent a messenger to Athens, and gave back the dead to the Thebans under a truce, and arranged matters in the city to suit their present circumstances, as seemed best to them.—Now news had immediately been taken to the Athenians of what had been done with respect to the Plataeans;

and they straightway seized as many of the Boeotians as were in Attica, and sent a herald to Plataea, with orders to forbid their proceeding to extremities, in the case of the Thebans whom they had in their hands, till they also should take counsel about them:

for tidings of their being dead had not yet reached them. For the first messenger [of the Plataeans] had gone out at the very time of the entering of the Thebans; and the second, when they had just been conquered and taken: so that of the subsequent events they knew nothing. Thus then the Athenians were in ignorance when they sent their order; 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 it, and took out the least efficient of the men with the women and children.