Book 1, Chapter 2 — Causes of the War—The Affair of Epidamnus—The Affair of Potidæa
A colonial quarrel in a city most Athenians had never heard of drags two empires toward war.
Summary
The affair at Epidamnus, a Corcyraean colony on the Illyrian coast, begins with an unremarkable internal crisis: the democratic faction expels the oligarchs, the oligarchs ally with the local Illyrian tribes, and the city asks Corcyra for help. Corcyra refuses. Epidamnus then turns to Corinth, Corcyra's own mother city — a calculated insult. Corinth, partly from genuine colonial obligation and partly from long-standing irritation with Corcyra, accepts. What follows is a naval confrontation at Sybota in which Athens, persuaded by Corcyra's arguments about the strategic value of its fleet, sends ships to the battle with instructions to fight only defensively. The distinction collapses immediately in the confusion of combat.
The Potidaean affair adds a second layer of grievance. Potidaea is a Corinthian colony but a tribute-paying member of the Athenian alliance; it receives its annual magistrates from Corinth. When Athens, suspicious of Corinthian influence after Sybota, demands that Potidaea pull down its seaward wall and expel its Corinthian magistrates, the city revolts, supported by Corinthian volunteers. The Athenians besiege it. Corinth now has two grievances against Athens, and the stage at Sparta is set for the confrontation Thucydides regards as the real engine of the war: Spartan fear of Athenian power, confirmed by Athenian behavior in these two episodes.
Thucydides's account of the immediate causes is a masterwork of structural argument. He distinguishes throughout between the pretexts — Epidamnus, Potidaea — and the truest cause, which he states plainly: it was the growth of Athenian power and the fear this inspired in Sparta that made war necessary. The intervening disputes gave each side the legal and emotional justification it needed. The pretexts are real; the speeches at Sparta are genuine; the grievances on both sides are not manufactured. But they are grievances against a background of structural tension that would have found some other pretext if these had not occurred. This two-level analysis — surface cause and deep cause — is one of the foundations of modern political history.
- Book 1Book 1 opens not with battle but with argument.
- Book 1The immediate causes of the war begin with Epidamnus — a small colony on the Adriatic whose civil strife triggers a chain of interventions that pulls Corinth against Corcyra and Corcyra toward Athens.
- Book 1The congress at Lacedaemon is the Peloponnesian War's diplomatic overture.
- Book 1The Pentecontaetia — the fifty years between the Persian Wars and the outbreak of the Peloponnesian War — is Thucydides's compressed account of how Athens turned from war-leader to empire.
- Book 1Chapter 5 is the last diplomatic chapter before war breaks out.
- Book 2The war formally begins with the Theban attack on Plataea.
- Book 2The plague of Athens is the History's most famous sustained passage outside the Funeral Oration.
- Book 2Chapter 8 covers the third year of the war across multiple theatres.
- Book 3Book 3 opens with the revolt of Mytilene, the largest and most strategically significant of the Athenian allied cities.
- Book 3Two episodes in Book 3's second half illustrate what civil and inter-state war does to the norms that normally govern violence.
- Book 3Chapter 11 follows the Athenian general Demosthenes through a remarkable arc: from the catastrophic defeat in Aetolia, where he led light-armed Athenian troops into wooded hill country they were utterly unequipped to fight in and lost the greater part of them, to the brilliant campaign in Acarnania, where he used his knowledge of irregular warfare, learned at severe cost, to ambush and nearly annihilate a Peloponnesian and Ambraciot force.
- Book 4The Pylos campaign is the tactical and psychological turning point of the war's first decade.
- Book 4Chapter 13 moves across multiple theatres in the war's seventh and eighth years.
- Book 4Book 4's final chapter belongs to Brasidas — the one Spartan commander who combined military brilliance with political intelligence, the qualities Sparta as an institution consistently undervalued.
- Book 5The tenth year of the war produces one of history's more striking coincidences of elimination.
- Book 5The peace after Cleon and Brasidas is a peace in name only.
- Book 5The Melian Dialogue is ten pages in most editions and has been discussed for two and a half thousand years.
- Book 6Book 6 opens with the debate and vote on the Sicilian Expedition — one of the History's great scenes of collective irrationality.
- Book 6While the Athenian expedition crosses the sea, Syracuse holds its own debate about whether to believe the threat.
- Book 6With Alcibiades gone and Lamachus increasingly the operational commander, the Athenian force finally moves seriously against Syracuse in the expedition's second year.
- Book 7Book 7 opens with the Athenian position deteriorating on every front simultaneously.
- Book 7Demosthenes arrives with the reinforcements and immediately does what Nicias had been unable to do: he assesses the situation, decides on a bold stroke, and acts.
- Book 7Book 7's final chapters are the most sustained tragic narrative in classical literature.
- Book 8Book 8 opens with Athens after Sicily — a city that could not believe what it had done to itself, then could not stop the consequences.
- Book 8Chapter 25 covers one of the strangest episodes in Athenian history: the oligarchic revolution of 411 BCE, in which a conspiracy of four hundred men overthrows the Athenian democracy at the city's moment of maximum strategic vulnerability.
- Book 8The History's final chapter covers the collapse of the Four Hundred, the restoration of a modified democracy in Athens, the recall and rehabilitation of Alcibiades, and the Athenian naval victory at Cynossema — a victory that demonstrates Athens's ability to recover even now.