swore a solemn oath to maintain the independence of the city. But the
Thebans had never forgotten or forgiven the secession of Plataea from
the confederacy of which they were the leaders; and seizing the
opportunity while the Athenians were occupied with measures for their
own safety, they made a treacherous attempt to gain possession of the
town.

On a dark and moonless night in the early spring three hundred armed
Thebans appeared before the gates of Plataea, which were opened to
them by a party of the citizens who favoured their design. Marching in
a body to the market-place, they made proclamation by a herald,
inviting all who chose to return to their allegiance, and take sides
with their lawful leaders, the Thebans. For they wished, if possible,
to gain over the place without bloodshed, and before the war had
actually broken out; otherwise, they might have to give it up again on
the conclusion of peace.

The Plataeans, being wakened out of their first sleep, and thinking
that the Thebans were in much greater force than was really the case,
at first attempted no resistance, but were disposed to accept the
terms offered them. But perceiving by degrees that their enemies were
far weaker in numbers than themselves, they changed their minds, and
resolved to attack them. For the party which had betrayed the town was
but small, and the general body of the citizens detested the thought
of falling once more under the supremacy of Thebes. Their measures
were taken with great secrecy and despatch: to avoid exciting the
suspicions of the Thebans, they broke down the dividing walls of their
houses, and passed to and fro unobserved, until they had completed
their preparations. To embarrass the movements of the Thebans, they
barricaded the streets with waggons, and then, just before daybreak,