This first peace was broken, of course, with Sparta's refusal to attend the Congress called for by Pericles, followed by the revolt of Boeotia. Athens agreed and both sides signed a defensive treaty. For full treatment, see Ancient Greek civilization: The Peloponnesian War. The Athenian alliance was, in fact, an empire that included most of the island and coastal states around the northern and eastern shores of the Aegean Sea. A brief treatment of the Peloponnesian War follows. The truce is extended 30 years, Megara is returned to the Peloponnesian League, and both sides agree to respect the alliances of the other. Other articles where First Peloponnesian War is discussed: ancient Greek civilization: Friction between Athens and Corinth: …what modern scholars call the First Peloponnesian War. The First Peloponnesian War The first Peloponnesian war started when Corcyra (Corfu), which was having a conflict with Corinth (its Mother City), asked Athens for help.