In the following spring he fastened a quarrel upon Potidaea, a town in Chalcidice, which was attached by ancient bonds to Corinth, and in the campaign which followed Athenian and Corinthian troops came to blows.
It corresponded roughly to ancient Thrace, Macedonia with Chalcidice, Epirus and a large part of Illyria, constituting the present administrative divisions of Stambul (Constantinople, including a small strip of the opposite Asiatic coast), Edirne (Adrianople), Salonica with Kossovo (Macedonia), Iannina (parts of Epirus and Thessaly), Shkodra (Scutari or upper Albania).
Seleucus Nicator gave it a Macedonian name, Beroea; but Chalcis, some distance S., was the capital of the province, Chalcidice (later, Kinnasrin), in which it lay, and the centre of that hellenized region, now a.
In the 8th and 7th centuries it founded thirty townships on the peninsula of Chalcidice, and several important cities in Sicily.
Potidaea, a Dorian town on the western promontory of Chalcidice in Thrace, a tributary ally of Athens - to which however Corinth as metropolis still sent annual magistrates - was induced to revolt,' with the support.
The Athenians failed in an expedition to Chalcidice under Xenophon, while the Spartan Cnemus with Chaonian and Epirot allies was repulsed from Stratus, capital of Acarnania,.
Though originally dependent on Eretria, by the 7th century B.C. it had become sufficiently prosperous to send out several colonies to Chalcidice (Acanthus, Stageirus, Argilus, Sane).