History of the Peloponnesian War

The Potidaeans having sent ambassadors to Athens to try if they could persuade the people not to make any alteration amongst them, by other ambassadors, whom they sent along with the ambassadors of Corinth to Lacedaemon, dealt with the Lacedaemonians at the same time, if need required, to be ready to revenge their quarrel. When after long solicitation at Athens and no good done, the fleet was sent away against them no less than against Macedonia, and when the magistrates of Lacedaemon had promised them if the Athenians went to Potidaea, to invade Attica, then at last they revolted, and together with them the Chalcideans and Bottiaeans, all mutually sworn in the same conspiracy.

For Perdiccas had also persuaded the Chalcideans to abandon and pull down their maritime towns and to go up and dwell at Olynthus and that one city to make strong, and unto those that removed gave part of his own and part of the territory of Mygdonia, about the lake Bolbe, to live on so long as the war against the Athenians should continue. So when they had demolished their cities and were gone up higher into the country, they prepared themselves to the war.