Outbreak of the Peloponnesian War (Archidamian War begins)
In 431 BCE, Sparta and its allies went to war with Athens, opening the Archidamian phase of a conflict that would last until 404. Smoke rose over Attica as hoplites marched and triremes beat toward the Saronic Gulf. Thucydides called Spartan fear of Athenian growth the war’s root cause.
What Happened
Athens’ marble glittered; Sparta’s patience thinned. By 431 BCE, disputes from Corcyra to Potidaea masked a simpler equation—Sparta’s fear of an alliance turned empire, and Athens’ refusal to yield what it had built afloat. The Peloponnesian League voted for war, and King Archidamus led Spartans and allies into Attica, inaugurating the Archidamian War [11][18].
Attic farmsteads emptied as citizens crowded behind the Long Walls connecting Athens to Piraeus. The sound of gates slamming and children crying replaced the creak of olive presses. Outside, Spartan hoplites burned the countryside. Inside, Pericles urged strategy, not rage: avoid pitched battle on land, lean on the fleet, protect the grain lifeline from the Hellespont, and let time grind the enemy [1][11].
Thucydides, the exile-historian who would record the war’s phases, wrote the famous diagnosis: “The growth of the power of Athens, and the alarm which this inspired in Lacedaemon, made war inevitable.” The naval alliance had become an administrative machine; the machine had become a threat. Athens could raise ships and money with a speed clerks could tally and enemies could feel [11][18].
Pericles’ first winter oration, recorded by Thucydides, rang with civic pride: equal justice, merit over birth, a city that loved beauty without softness. The words echoed up the Pnyx as the azure winter sky crisped above the Acropolis’ scaffolds. Then plague came, and the rhetoric met the human cost of crowding and war, turning confidence into endurance [1][11].
At sea, Athenian squadrons probed the Peloponnesian coast, their bronze rams gleaming, their oars thudding in drilled unison. In the Agora, juries still drew lots, and tribute still arrived. But the war’s arithmetic grew harsher with each campaigning season. Allies questioned value; enemies found new funds.
The first phase ended not with decision but exhaustion. The Peace of Nicias, chiselled onto pillars across Greece in 421, would promise a pause. But the logic of fear and advantage that had produced smoke over Attica would not release its grip for long [2][11].
Why This Matters
War shifted Athens’ institutions onto a wartime footing, validating Pericles’ naval strategy—defend by sea, pay for mass participation, and endure behind walls. It tested the alliance-turned-empire as revenue source and as diplomatic liability [1][11][18].
Within War, Diplomacy, Realpolitik, the outbreak illustrates structural causes—Spartan fear meeting Athenian consolidation—and the interplay between treaties and coercion that would recur in the Peace of Nicias and the Melian episode [2][11].
The conflict’s phases—Archidamian war, unstable peace, Sicilian disaster, Ionian/Decelean war—form the backbone of the Golden Age’s rise and fall. Athens’ reliance on sea power and grain from the Black Sea would define both resilience and vulnerability [11][18].
Thucydides’ analysis keeps scholars focused on power transitions and perceived intent. The opening frames debates about hegemony that reach from Delos’ treasury to Aegospotami’s shore [11].
Event in Context
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People Involved
Key figures who played a role in Outbreak of the Peloponnesian War (Archidamian War begins)
Pericles
Pericles was the leading statesman of mid-fifth-century BCE Athens, born to the general Xanthippus and the Alcmaeonid noble Agariste. Trained by thinkers like Anaxagoras and the music theorist Damon, he married intellect to political craft, using Delian League revenues to fund juries, festivals, and a spectacular civic building program. He pushed the 451 citizenship law, moved the league treasury to Athens, and oversaw the Parthenon’s construction under Phidias. When the Peloponnesian War began, Pericles argued for a maritime strategy and articulated Athens’ civic creed in his Funeral Oration. His leadership fused empire, art, and democracy—raising the question central to this timeline: could Athens sustain power at sea without eroding the ideals it proclaimed?
Thucydides
Thucydides, an Athenian aristocrat with Thracian ties and income from gold mines, served as a general in 424 BCE and was exiled for failing to save Amphipolis. Exile made him the war’s most penetrating observer. In his History of the Peloponnesian War he chronicled the outbreak, the Funeral Oration, the Melian Dialogue, and the Sicilian Expedition with a new, unsparing method: speeches reimagined to reveal motives, and events analyzed for causes, power, and fear. He belongs in this timeline as its conscience and clinician, the writer who showed how a maritime democracy could mistake empire for security and discover the cost in plague, hubris, and strategic overreach.
Aristophanes
Aristophanes, the master of Old Comedy, turned Athenian politics into uproarious theater. Debuting in the 420s BCE, he mocked demagogues, generals, and the city’s thirst for empire with choruses, slapstick, and razor satire. The Acharnians (425) begged for peace; Knights (424) savaged Cleon; later works skewered the Sicilian folly and war weariness. In an age when fleets and festivals drew on the same tribute, Aristophanes made the stage a civic arena where Athenians could hear their own contradictions sung and shouted. He belongs in this timeline as the chorus to empire—cheering the city’s brilliance, jeering its hubris, and reminding a maritime democracy what it risked becoming.
Nicias
Nicias was a conservative Athenian general and one of the richest men in the city, famed for piety and caution. He rose during the Archidamian War, captured Cythera, and balanced aggressive rivals like Cleon and Alcibiades. In 421 BCE he negotiated the Peace of Nicias, a fragile truce meant to last fifty years. Yet he later co-commanded the Sicilian Expedition he had opposed; after delays and a fateful lunar omen in 413, his shattered army surrendered at Syracuse. Executed by the victors, Nicias became the tragic face of a maritime democracy that mistook resources for invincibility.
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