On the isthmus of that lesser peninsula called Pellênê, which forms the westernmost of the three prongs of the greater peninsula called Chalkidikê, between the Thermaic and the Strymonic gulfs, was situated the Dorian town of Potidæa, one of the tributary allies of Athens, but originally colonized from Corinth, and still maintaining a certain metropolitan allegiance towards the latter: insomuch that every year certain Corinthians were sent thither as magistrates, under the title of Epidemiurgi. On various points of the neighboring coast, also, there were several small towns belonging to the Chalkidians and Bottiæans, enrolled in like manner in the list of Athenian tributaries. The neighboring inland territory, Mygdonia and Chalkidikê,[113] was held by the Macedonian king Perdikkas, son of that Alexander who had taken part, fifty years before, in the expedition of Xerxes. These two princes appear gradually to have extended their dominions, after the ruin of Persian power in Thrace by the exertions of Athens, until at length they acquired all the territory between the rivers Axius and Strymon. Now Perdikkas had been for some time the friend and ally of Athens; but there were other Macedonian princes, his brother Philip and Derdas, holding independent principalities in the upper country,[114] apparently on the higher course of the Axius near the Pæonian tribes, with whom he was in a state of dispute. These princes having been accepted as the allies of Athens, Perdikkas from that time became her active enemy, and it was from his intrigues that all the difficulties of Athens on that coast took their first origin. The Athenian empire was much less complete and secure over the seaports on the mainland than over the islands:[115] for the former were always more or less dependent on any powerful land-neighbor, sometimes more dependent on him than upon the mistress of the sea; and we shall find Athens herself cultivating assiduously the favor of Sitalkês and other strong Thracian potentates, as an aid to her dominion over the seaports.[116] Perdikkas immediately began to incite and aid the Chalkidians and Bottiæans to revolt from Athens, and the violent enmity against the latter, kindled in the bosoms of the Corinthians by the recent events at Korkyra, enabled him to extend the same projects to Potidæa. Not only did he send envoys to Corinth in order to concert measures for provoking the revolt of Potidæa, but also to Sparta, instigating the Peloponnesian league to a general declaration of war against Athens.[117] And he farther prevailed on many of the Chalkidian inhabitants to abandon their separate small towns on the sea-coast, for the purpose of joint residence at Olynthus, which was several stadia from the sea. Thus that town, as well as the Chalkidian interest, became much strengthened, while Perdikkas farther assigned some territory near Lake Bolbê to contribute to the temporary maintenance of the concentrated population.