Build-up to the First Peloponnesian War: 478-460 BC

Sparta is having difficulty in retaining the loyalty of the members of its own Peloponnesian League, several of whom adopt democratic governments hostile in principle to the Spartan oligarchy.

Sparta's troubles are compounded by a devastating earthquake in 464. Indirectly it brings to a head the simmering hostilities between Sparta and Athens.

The earthquake destroys much of the city of Sparta and kills many Spartiates - the Greek term for Sparta's warrior citizens. The Helots seize the opportunity to rise in revolt. The Spartans manage to contain the rebels in the region of Mount Ithome, in Messenia, but they lack the strength to defeat them. They appeal to their allies for help.

Athens, at this stage technically an ally of Sparta, is among the city-states which send an army.

Instead of welcoming this Athenian support, the Spartans send the soldiers back to Athens without involving them in the campaign. The precise reason is not known, but is probably political. The decision follows the news that Athens is in the process of introducing a more Radical democracy, a measure profoundly offensive to aristocratic Sparta. The episode is interpreted as a snub by the Athenians, who are constitutionally inclined to distrust Sparta.

Soon after this event Athens makes provocative alliances with two city-states opposed to Sparta. Open hostility breaks out in 460, the year commonly taken as the start of the First Peloponnesian War.

The First Peloponnesian War: 460-446 BC

In the early years of the First Peloponnesian War the fighting is mainly between Athens and the northern states of the Peloponnese, in particular Corinth. A significant gain for Athens is the capture in 457 of the large island of Aegina, occupying a strategically important position directly between Athens and the Peloponnese in the centre of the Saronic Gulf.

Sparta intervenes for the first time in this same year, defeating the Athenians close to home at Tanagra.

The Thirty Year Treaty: 446-431 BC

The war drags on inconclusively. Athens finds it hard to consolidate any gains which she makes on land, but her superior naval power means that she can regularly raid the towns of the Peloponnesian coast.

In 446 a Thirty Year Treaty is agreed. It recognizes two distinct spheres of influence. The empire of Athens is the Aegean Sea. Its tributary states are round the coasts and on the islands (the one gain of the war is Aegina, which remains with Athens). By contrast Sparta's allies are the land states of the Peloponnese and central Greece. Neither side, it is now agreed, will commit an act of aggression against any part of the other. The treaty holds until Athens tests it severely, in 433, in relation to Corcyra.

The large island of Corcyra (Corfu, off the northwest coast of Greece) is in origin a colony of Corinth. But it is now a powerful state in its own right, and in 433 BC it is at war with Corinth. The Corcyrans turn for help to the only Greek fleet which can match that of Corinth. They appeal to Athens.

The first response of the Athenian assembly is caution. But an ally in the western sea, close to the heel of Italy, is an attractive proposition. Pericles persuades the assembly to send thirty triremes for defensive purposes only, arguing that this will not breach the treaty.

Events prove Pericles wrong. Hostilities escalate to the point where Athenian ships are blockading an ally of Corinth (Megara) and threatening a Corinthian colony (Potidaea). In 432 the Spartans decide that Athens is guilty of aggression. They send an envoy demanding withdrawal of the Athenian ships.

Pericles again is among the hawks. He persuades the assembly to reply that Athens will never bow to an ultimatum from Sparta, but will agree to independent arbritration. Diplomatic stalemate ends in 431 when Thebes, an ally of Sparta, suddenly attacks Plataea, an ally of Athens. The Second Peloponnesian War, often known simply as the Peloponnesian War, has started.

The Second Peloponnesian War: 431-404 BC

The twenty-seven years of the war form a complex web of shifting alliances and fluctuating fortunes for the two main contestants, Sparta and Athens, with a high level of treachery and brutality as an accepted norm.

The underlying pattern of hostilities is a dispiriting routine based on two unchangeable facts: a Spartan army is almost irresistible in battle; but the famous Walls of athens, and her powerful fleet (protecting respectively both city and harbour), mean she is impregnable. So every summer the Spartans march north and spend a month destroying all the Athenian crops, while the farmers shelter in the city. The Athenian navy then has to bring in even more corn than is normally required.

The second summer of this kind, that of 430, is made more painful for the Athenians because plague strikes the city and kills nearly a third of the inhabitants. Thucydides catches it, but survives to write his great history of the war. Pericles, architect of the Athenian war strategy, is less lucky; he falls victim in the second summer of the plague, 429.

Yet Athens survives even this catalogue of disasters, and by 425 Sparta seems the underdog - suffering a series of defeats close to home in the Peloponnese, at the hands of soldiers landing from Athenian ships. It appears as though neither side can ever win this conflict.

Mytilene and Melos: 427 and 416 BC

Meanwhile certain engagements have been so dramatic that they acquire the status of classic scenes, as written up by Thucydides. One is the event which began the war, the siege of Plataea.

Another is the case of Mytilene, an allied city which rebels against Athens in 428. It is forced into surrender in 427, whereupon the assembly in Athens votes that all adult males in Mytilene shall be killed and their women and children sold into slavery. The next day the issue is debated again and the vote, by a narrow majority, goes the other way. Now only those considered directly responsible for the revolt are to be killed.

Thucydides vividly describes the drama as a second trireme is sent off on a desperate mission of mercy. It manages to arrive within minutes of yesterday's ship, bearing the sentence of death. Even so, the number executed for the crime of rebellion amount to more than 1000 men in this relatively small community.

The case of Melos shows Athens in an even more brutal light. This small island, originally a colony of Sparta, offends Athens by insisting on neutrality. It is therefore an unwelcome exception in the Aegean, where nearly all the islands are in the Athenian camp. In 416 an Athenian force lands on the island and besieges the city.

The citizens of Melos refuse to give in to Athenian demands for tribute. They are besieged and eventually overwhelmed, whereupon all the males of the island are killed, the women and children are taken away as slaves, and Melos is given to 500 Athenian settlers.

Such an outcome, a classic example of what is described 2500 years later as a war crime, seems profoundly shocking when perpetrated by Athens, the paragon of classical civilization. But it is not an unusual end to a siege in this disastrous war. Such a fate is always a possibility facing any Greek city-state which allows itself to be overwhelmed by another.

Sicilian expedition and the triumph of Sparta: 415-404 BC

It has seemed that neither Sparta nor Athens will ever have the strength to subdue the other. But from 415 the pattern changes. In that year Athens attempts an expedition to Sicily, hoping to capture the Corinthian colony of Syracuse and thus acquire another source of much needed grain. The result is a disaster. Defeat by the Syracusans costs Athens 200 warships and some 40,000 men.

In the following year, 414, the Persians begin to take a renewed interest in the Aegean. Prompted by Alcibiades (a headstrong Athenian who is history's outstanding turncoat), the Persian emperor begins funding a Spartan navy to rival that of Athens.

Persia wishes to regain control of the Greek cities of Asia Minor, which are firmly in the Athenian camp and towards which Sparta feels no obligations. Once an alliance is established between Sparta and Persia, the defeat of Athens is to the equal benefit of each.

The end comes suddenly, in 405. The surviving Athenian fleet is surprised and destroyed by the Spartans in the Hellespont. For the first time in 100 years Athens has lost control of the Aegean Sea. The result is that she cannot feed herself. A Spartan blockade of the land routes through Attica hastens the inevitable capitulation, in 404.

Sparta's terms are lenient by the standards of the time, reflecting perhaps the prestige of Athens - even to her enemies - as the centre of Greek culture. No one is killed, no temples are destroyed.

But the Long Walls and the defences of the Piraeus, always an affront to the Spartans, are systematically demolished. And the Athenians have to swallow a bitter pill in acknowledging the rule of Sparta - though not for long, as it turns out. An Athenian oligarchy imposed by Sparta rules the city with such harsh injustice that the democratic faction recovers control after just a year, in 403. But one indirect result of these events, four years later, is the death of Socrates.