History of the Peloponnesian War

Now the Potidaeans sent ambassadors to the Athenians, to try if by any means they might persuade them to adopt no new measures against them; and went also to Lacedaemon in company with the Corinthians, to provide themselves with assistance, should it be necessary; and when, after long negotiating, they obtained no favourable answer from the Athenians, but the ships commissioned against Macedonia were sailing just as much against them and when the authorities at Lacedaemon promised them, that should the Athenians go against Potidaea, they would make an incursion into Attica; then indeed, at that favourable moment, they revolted with the Chalcidians and Bottiaeans, having entered into a league together.

And Perdiccas persuaded the Chalcidians to abandon and throw down their cities on the sea, and remove inland to Olynthus, and make that one city a place of strength for themselves. And to those who abandoned them he gave a part of his own territory in Mygdonia, round lake Bolbe, to enjoy as long as the war with the Athenians lasted. And so, throwing down their cities, they removed inland, and prepared for war.