What and when was the Peloponnesian War?

During the fifth century BC, battles raged on land and at sea in a protracted and bloody conflict between the two leading city-states of ancient Greece: Athens and Sparta. On one side was the supreme naval power of Athens and on the other the dominant Spartan army, with each heading an alliance that involved nearly every single Greek state. The Peloponnesian War of 431-404 BC would reshape the Hellenic world.


How do we know about the Peloponnesian War?

The pre-eminent account of the war was written by Thucydides, who, despite serving as a general in the Athenian army, is remembered as a forefather of impartial historical study. He began his masterly work, The History of the Peloponnesian War, in the first year of the conflict, 431 BC, “believing that it would be a great war and more worthy of relation than any that had preceded it”.

Although the war, and Thucydides’ work, came to be named after the peninsula of Greece where Sparta and some of its allies were located, the fighting was not confined to the Peloponnese. Battles also devastated the Aegean coastline, the island of Sicily and the Attica region.

Were Athens and Sparta once allies?

Yes, Athens and Sparta had fought side by side against the Persian invasions of Greece by Darius and then his son Xerxes in the early fifth century BC. Allied Greeks defeated them first at Marathon and then at the battles of Salamis, Mycale and Plataea, crushing the invasions.

What was the Delian League?

In the aftermath, in 478 BC, an alliance of Greek states called the Delian League was formed as protection against any future Persian attacks. Hundreds of states joined the Delian League, but it came to be so dominated by Athens that the Athenians effectively turned the alliance into an empire. Circling the Aegean Sea, the Athenian Empire built a huge navy of triremes – galleys, more than 30 metres long and with three lines of rowers down the length of each side, capable of great speeds – making Athens the dominant maritime power in Greece.

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Sparta grew alarmed at Athens’ hegemony, which continued to expand due to regular tributes pouring in from across the empire. Athens also planned to rebuild the ‘Long Walls’ – miles of fortifications connecting the city to the harbour of Piraeus – so as to offer a link to the sea even at times of siege, making it yet more powerful.

What was the Peloponnesian League?

While Athens ruled the seas, Sparta had long headed its own alliance of states from the Peloponnese and central Greece – the Peloponnesian League – which commanded a stronger army thanks to much-feared and respected Spartan warriors.

Why were the Spartans such great warriors?

The lives of Spartan men were consumed by military service and commitment to winning glory in battle. Their constant and brutal training began at the age of seven, when boys would be sent from their families to undergo the ritual of agoge, a form of boot camp. This turned them into a fiercely disciplined and highly trained fighting force, feared across all Greece. During the Persian invasions of the fifth century BC, Sparta had shown its might when 300 warriors and an alliance of Greek city-states, led by King Leonidas, had fought the Persian army at the battle of Thermopylae.

Why did the Peloponnesian War start?

Fighting had raged for decades before the Peloponnesian War, as Athens and Sparta got involved in the conflicts of other states or exploited circumstances to further their own advantage. This period, sometimes called the First Peloponnesian War, ended with the Thirty Years’ Peace in the winter of 446/45 BC – although the uneasy peace lasted only half that time.

Athens continued its aggression during the 430s, siding against Corinth, an ally of Sparta, by sending ships to assist its own ally, Corcyra, at the battle of Sybota. Athens then further tested the limits of the peace treaty by laying siege to the Corinthian colony of Poteidaia and issuing, in c432 BC, the Megarian Decree, which essentially imposed a trade embargo on another long-time Spartan ally, Megara. Even then, Sparta did not immediately retaliate, as it honoured the peace and was unready for a long conflict. But war was brewing.

What was Sparta’s plan?

When war finally broke out in 431 BC, Sparta had the lofty aims of liberating Greece from Athenian tyranny and dismantling its empire. Attacking over land, King Archidamus II led an army of hoplites, armed with spears and shields, into the Attica peninsula, leaving destruction and chaos in his wake and robbing Athens of vital resources. He hoped to provoke the enemy and draw them out from their fortified walls into open battle, but Athens refused to take the bait thanks to the guidance of influential statesman Pericles. Instead, Athens used its superior navy to harass Spartan ships and make its own assaults in the Peloponnese.

Were there really only 300 Spartans at the battle of Thermopylae?

It is true there only 300 Spartan soldiers fought at Thermopylae, but they were not alone...

A sculpture dedicated to King Leonidas of the Spartans in Thermopylae, Greece. (Photo by iStock/Getty Images Plus)

Were the Athenians right not to invite open battle?

Even though it may have been regarded as cowardice by the enemy, remaining behind the walls was a savvy move. But disaster struck when Athens was ravaged by plague. Outbreaks wiped out a huge proportion of the population – perhaps as many as a quarter, or around 100,000 people – and decimated the Athenian leadership. Pericles himself succumbed in 429 BC.

The plague is thought to have come from sub-Saharan Africa, reaching Athens through the port of Piraeus; the added burden of people from Attica arriving to escape the Spartans only served to spread the disease faster. The fortifications that were keeping Athens safe in war were now keeping the plague inside. The Spartans did not approach the city for fear of catching it themselves, but they simultaneously refused the Athenian calls for peace.

Yet Sparta failed to take advantage of a much-weakened Athens as its campaigns on land and sea suffered setbacks. Then when the island of Lesbos looked like rising up in revolt against Athens, which resulted in a blockade being put in place, the Spartans failed to come to their assistance and the island surrendered. In 427 BC, however, Sparta did capture the strategic Athenian ally of Plataea following a lengthy siege.

Did either side gain the advantage?

With the cautious Pericles gone (he died in 429 BC) and the hawkish Cleon taking over, Athens embarked on a more aggressive strategy. One of the finest generals of the day, Demosthenes, commanded raids on the Peloponnese; he was given a fleet with which he occupied and fortified the remote headland of Pylos; and repelled the assault to win it back. The building of outposts on the Peloponnese created a different problem for Sparta: the Athenians used them to attract runaway helots, or slaves, meaning there were fewer people to work the fields and a higher chance of a slave revolt.

As more battles went against them Sparta began suing for peace itself, until terms became more favourable when it achieved victories of its own. The most significant came in 422 BC with the capture of the Athenian colony of Amphipolis. The man Athens had sent to protect it was Thucydides – for his failure, he was exiled and dedicated his time to his impartial history of the war. The distinguished Spartan general Brasidas died in the fight for Amphipolis, as did Athens’ Cleon, leaving the way clear for those, on both sides, who desired peace.

How long did peace last?

The resulting Peace of Nicias – named after the man from Athens sent to negotiate the treaty – was signed in 421 BC. Intended to last 50 years, it ended up lasting just six. In fact, fighting never really stopped, as both sides spent those years trying to win over smaller states, or watched on as allies formed coalitions of their own and kept the conflict going.

In 415 BC, war officially resumed when Athens launched a massive assault on Sicily with the aim of capturing Syracuse, a powerful city-state which controlled a large share of Mediterranean trade. If successful, Athens could claim its abundant resources.

The expedition started badly, however, as the Athenian commander Alcibiades, who had been accused of the serious crime of impiety and ordered back to Athens, defected to Sparta. Syracuse, with Spartan aid, broke the blockade around Sicily and time and time again defeated the invading army until it was crushed, even in a sea battle.

By 413 BC, the few who had not been killed or enslaved were forced to retreat. The invasion was a total disaster for Athens, a major blow to morale and prestige.

Did the failure of the Sicily expedition swing the tide?

Back in Greece, Sparta certainly looked to be closer to victory over the next few years as it occupied Attica once again and several revolts broke out against Athenian rule. Athens itself was in political turmoil as governments were overthrown and replaced. What’s more, the Persians had chosen to back Sparta as they saw the Athenian empire as a threat.

And yet, the Spartans and their allies were slow to act, allowing Athens to rebuild and put into service its reserve navy. Athens started winning naval battles again, so much so that by 406 BC, it had actually won back parts of the empire thought to have been lost.

What effect did the Peloponnesian War have on democracy in ancient Greece? Find out in our guide to the history of democracy

Solon, an Athenian statesman (left) laid the foundations for democracy

How did the war finally end?

It would be a naval victory that won the Peloponnesian War after 27 years, but not an Athenian one. Sparta managed to build an imposing fleet of hundreds of triremes, thanks to Persian money and resources, and put to sea. In 405 BC, the fleet – under the skilled command of Lysander – crushed the Athenians at the battle of Aegospotami, near the Hellespont. Lysander then advanced to Athens itself and forced the city-state to surrender the following year. The victorious Spartans ordered the Long Walls to be demolished, forbade Athens from building a fleet larger than 12 ships and demanded Athens pay them tribute. The Athenian empire was no more; Sparta had emerged as the dominant power in Greece.

What happened in Greece after the war?

Sparta’s position did not last long. It became embroiled in too many conflicts for its army to handle, and its hold over Greece ended with defeat by Thebes and its Boeotian League allies at the battle of Leuctra in 371 BC.

Nearly a century of the Peloponnesian War, followed by continued fighting and divisions, had left Greece vulnerable. This instability was exploited by Philip II of Macedon, who invaded and defeated the city-states – laying the foundations of a Macedonian empire, which would grow to an unprecedented size in the reign of his son, Alexander the Great.


This content first appeared in the Christmas 2020 issue of BBC History Revealed


Jonny Wilkes
Jonny WilkesFreelance writer

Jonny Wilkes is a former staff writer for BBC History Revealed, and he continues to write for both the magazine and HistoryExtra. He has BA in History from the University of York.