Peloponnesian War: Epidamnus, Corcyra & Potidaea

Instructor: Christopher Muscato

Chris has a master's degree in history and teaches at the University of Northern Colorado.

The Peloponnesian War was one of the greatest conflicts in Greek history, but how did it actually start? In this lesson, we'll look at the background of this war and see how a few relatively minor cities contributed to one of Greece's biggest wars.

The Peloponnesian War

Ancient Greek history is full of important battles. Some were fought against foreign invaders, but most were actually fought between the various city-states of Greece themselves. One of the largest of these conflicts was the Peloponnesian War, which raged from 431-404 BCE. Most of what we know of this comes from the Greek historian Thucydides, who lived through the war and recorded its events (up through the year 411 BCE).

Most of our knowledge about the Peloponnesian war comes from Thucydides

The reason for the war was that Athens had started building an empire around the Aegean Sea and was growing too strong. The other superpower of the region, Sparta, fought to stop Athenian expansion, and the other Greek city-states were drawn in by the gravity of the situation. So, at its most basic, the Peloponnesian War was fought between the Athens/its allies and Sparta/its allies. However, the war didn't start in either Athens or Sparta. Like so many wars in world history, the actual origins are in a much smaller conflict that escalated across the Aegean.


The story of the Peloponnesian War begins in the relatively minor Greek city-state of Epidamnus, which had been dealing with some domestic issues. In the 430s BCE, the people broke into rebellion, overthrew the aristocracy, and established a new democracy. The aristocrats, eager to hold onto power, joined the nomadic enemies of Epidamnus and attacked the city. Epidamnus was not the strongest of cities, so the people sent ambassadors to a powerful neighbor with a massive navy: Corcyra. It was settlers from Corcyra who had founded Epidamnus, but the Corcyraeans were also one of the most politically neutral cities in Greece, so they decided not to help.

Still needing assistance, the Epidamnians went to another powerful city: Corinth. The Corinthians also had ancestral ties to Epidamnus, but more importantly, were squabbling with Corcyra. Corinth had founded Corcyra, and was still demanding that the younger city treat the older as a superior, despite the fact that Corcyra had become very wealthy and powerful on its own. So, Corinth decided to send troops to defend Epidamnus, partly as a snub to its former colony.

The Corcyraeans were furious with Corinth, and decided to send their ships to join the Epidamnian aristocrats in besieging the city. With 100 ships at their disposal, the Corcyraeans won the battle.


Despite this victory, Corcyra was very worried. They were traditionally a neutral city, staying out of Greek politics, but they'd gone to war against Corinth over the fate of Epidamnus. This was potentially a problem since Corinth was the most important ally of Sparta. Sparta at the time was the leader of an alliance of cities called the Peloponnesian League, founded to challenge Athens' growing power. Realizing that they could need allies as well, Corcyra went to Athens.

Athens decided to grant Corcyra an alliance, but only in the case that the city was being attacked. Their motivation was to keep Sparta from seizing Corcyra's massive navy, while remaining as neutral as possible. Athens sent a small fleet to Corcyra with orders to defend the city if necessary, but not to start anything. Not long after, however, Corcyraean and Corinthian ships started attacking each other near Sybota, not far from Corcyra itself. According to Thucydides, over 200 ships were involved in this battle, making it the largest maritime encounter up to that point in Greek history. Fearing that Corinth would try to attack Corcyra directly, Athenian ships entered the fight.


Both Corcyra and Corinth claimed victory in the Battle of Sybota, which was effectively fought to a stalemate. Athens, however, had now become involved in this fight and violated a long-standing neutrality treaty with Sparta. While Sparta still chose to stay out of this conflict, Athens assumed that Corinth would retaliate. The most likely spot was the city of Potidaea, a smaller ally of Athens but also a colony of Corinth that was located in a very strategic spot. Athens demanded that Potidaea dismiss the Corinthian diplomats and administrators in the city, as well as send Athens some Potidaean political prisoners to prevent the city from breaking their alliance.

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