The causes of the Second Peloponnesian War, 431 – 404 BCE – Part One:Background and the Atheno-Corcyraean Alliance

Our main source for the period of the Second Peloponnesian War is Thucydides’ ‘The History of the Peloponnesian War’. Thucydides himself was a member of the Athenian Aristocracy and was elected one of the 10 ‘strategos’ (generals) of the Athenians in 424BCE. He has the misfortune to be up against the brilliant Spartan general Brasidas, and his failure to rescue the city of Amphipolis resulted in his exile from Athens for 20 years. From Thucydides’ own words it seems his main aim in writing ‘The History’ was to provide a detailed account of the events of the war as he saw it. We cannot take everything he says as fact, and he embellishes and creates speeches in order to convey information about events. But regardless of that, Thucydides provides us with our best source of knowledge for this particular period of ‘Golden Age Ancient Greece’.

To understand the war, we first must understand the two sides. Since the routing of the Persian forces at the battle of Plataea in 479, the Athenians had created a naval empire, spanning the Aegean Sea and up into the Black Sea. The Spartans by contrast had created an informal empire, based around a system of alliances with other city states, known to posterity as the Peloponnesian league (not all states that were part of the league were situated in the Peloponnese, nor were all states in the Peloponnese members of the league). The growing power of Athens caused fear within the Spartan state; the two states were very different entities: Sparta was run along a strict military ideology, attempting to create the perfect warrior society. Athens, by contrast, was the leader of the democratic city states; the father of world democracy, the Athenians had owned a democratic system since the expelling of the tyranny in the late sixth-century BCE, and had established a dominant and powerful naval empire in the Aegean Sea in the course of the half century after the defeat of the Persians.

Thucydides states that there were four flashpoints that sparked the war, but rather than these being the sole reasons for the outbreak, he alludes to his belief that it was Spartan fear in the growth of Athenian power in the half century since the defeat of the Persians that caused the hostility and fighting that would become one of the greatest wars of the ancient world. In this short essay, I am going to focus on those flashpoints rather than the overriding cause, which will hopefully be looked at by myself another time.

The four flashpoints that Thucdides states as short-term causes of the war were:
The Athenian alliance with Corcyra
Issues with Potidaea
Aegina (we know little about this as Thucydides fails to explain)
The Megarian Decree

I will deal with each event in turn.

The Athenian Alliance with Corcyra


Corcyra was resident on the northern side of the island of Corfu and had been founded as a colony of the great city state of Corinth. In 435 a dispute broke out when the Corcyraean colony of Epidamnus sent an embassy to Corcyra begging for help against rebellious Epidamnian oligarchs and, when the Corcyraeans rebuffed their plea, they turned to the Corinthians for help. Thucydides tells us that the Corcyraeans sent a delegation to the Oracle at Delphi (the most senior religious Oracle in ancient Greece), who agreed that they should hand their city over to the Corinthians as a gift to ensure they received their assistance. They sent colonisers to the beleaguered city, but saw resistance from the Corcyraeans. War erupted and we know that the Corinthians suffered a defeat at the Battle of Leucimme in 435BCE, and when the Corcyraeans heard of the renewed Corinthian preparations to continue the war, they sent an embassy to Athens asking for an alliance. This was eventually granted, and brought Athens into a defensive alliance with Corcyra.

We must understand at this point why this alliance was such a momentous incident. There had been a previous proxy war between Sparta and Athens, and their allies, which ended in a treat in 446 proclaiming a 30 year truce. The clauses of this treaty stipulated that:
The two powers would keep their respective allies, meaning that if an ally rebelled from the alliance, if the other power were to accept her into their alliance they would be deemed to have broken the terms of the treaty.
Neutral powers – bar the historical enemy of Sparta, Argos – were free to join either alliance if they wished to.
No side was to make an aggressive move on the other if they latter wished the matter go to arbitration by neutral city states or the Oracle at Delphi.

Corinth, in her dispute with Corcyra, had aggressively attacked Corcyra even though the latter had asked for the matter of Epidamnus’ status be decided by arbitration. She again continued to break the terms when she attacked the Corcyraean and Athenian forces at the battle of Sybota. The Athenians by contrast made sure to avoid breaking the terms of the truce, and showed great restraint in order to allow the Corinthian forces to retreat unhindered from the battle. Terry Buckley argues that the Athenian decision to accept an alliance with Corcyra stemmed from a belief that a war between the Athenian Empire and the Peloponnesian League was inevitable, and to gain the advantage of the Corcyraean fleet was worth the risk. ( Buckley, Aspects of Greek History 750 – 323BC, (London; Routledge, 1996) p313)

In his account (Chapter 1), Thucydides uses long blocks of speech to explain much of the background to the decisions being made and arguments put forward at the Athenian Assembly. Thucydides tells us that after the Athenians allowed the Corinthians to leave the field at Sybota with their captured prisoners the Corinthians retired, leaving both sides claiming victory; the Corinthians had carried off over 1000 prisoners of war, including many important Corcyraean leaders, whilst Corcyra was left to maintain her free status.

The events with Corcyra left the relations between the Peloponnesian Leage, especially Corinth, and Athens in an extremely poor state. This event can be seen as the starting point of the descent into all out war. But it was only the starting spark. Next time I shall discuss the crisis over Potidaea, an Athenian ally, and the issues surrounding her.

Further Reading

Buckley, Aspects of Greek History 750 – 323BC, (London; Routledge, 1996)

Cartledge, The Spartans: An Epic History, (London; Macmillan, 2003)

Thucydides, ‘The History of the Peloponnesian War’, Translated by Richard Crawley, (Internet History Sourcebook)