History of the Peloponnesian War

The Athenians were to occupy Delium, the sanctuary of Apollo which is in the territory of Tanagra and opposite Euboea; and all these events were to take place simultaneously on an appointed day, in order that the Boeotians might not concentrate their forces at Delium, but that the several states might be occupied with their own disaffected districts.

And if the attempt should succeed and Delium should be fortified, they confidently expected, even if no immediate change occurred in the constitutions of the Boeotian states, nevertheless, so long as these places were in their possession, from which Boeotian territory could be ravaged and where everyone might find a convenient place of refuge, the situation would not remain as it was, but in time, when the Athenians should come to the support of the rebels and the forces of the oligarchs were scattered, they could settle matters to their own advantage.