According to Thucydides, it was bound to happen. ‘The growth of the power of Athens, and the alarm which this inspired in Lacedaemon [as ancient Sparta was known], made war inevitable,’ wrote the 5th-century BC Athenian historian and general in his History of the Peloponnesian War – the classic, eight-volume account of the conflict, which would later earn him the sobriquet the ‘father of scientific history’ for its impartial, evidence-based approach.

It was, of course, a civil war, stretching from 431 to 404 BC – an epic feud between the two leading city-states of the age that would go on to engulf almost the whole of the ancient Greek world, eventually spreading beyond the borders of modern-day Greece even as far as Sicily, the Dardanelles, and Cyprus. But the way it began, as a power struggle between ambitious rivals, with each pursuing influence through a complex system of armed alliances, has led some modern historians also to draw comparisons with other conflicts – not least, the outbreak of the First World War in 1914.
On one side were the conservative, agrarian Spartans – or, rather, the Spartan-led Peloponnesian League, founded in the 6th century BC, whose members included not only the major powers of the great Peloponnese peninsula but also those of central Greece. On the other was the fast-rising, democratic, Athenian-dominated Delian League, founded in 478 BC as a defence against Persian aggression, whose power was concentrated among the many islands and coastal states of the Aegean Sea.
Primarily a land-based power, Sparta had its main settlement on the banks of the Eurotas River in Laconia, in the south-eastern Peloponnese. Known for its austere military regime and obsessive focus on discipline, the city-state was home to the only fully professional army in Classical Greece – whose heavy infantrymen, called hoplites, were famed for the effectiveness of their phalanx formation. Such martial strength, however, came at a human cost – including the reduction of local subject populations to the status of helots (effectively state serfs), forced to work the fields on behalf of their hated Spartiate overlords.
For its part, Athens possessed the world’s greatest navy – a legacy of the Greco-Persian Wars (499-449 BC), during which it won a landmark naval victory over the much larger forces of King Xerxes I at the Battle of Salamis (480 BC). In the decades that followed, the prowess of the Athenian fleet allowed the increasingly influential city-state to establish maritime hegemony over the Hellenes, while the construction of the fortifications known as Long Walls helped to make it impregnable against attack.
As Paul Rahe explains in the first of two articles forming our special for this issue, it was against this backdrop that tensions between the two rival city-states would build inexorably in the aftermath of the Persian conflict, until the point at which they were to explode finally into open conflict. The war that followed – including the 418 BC Battle of Mantineia, described by Paul in his second article – saw power shift in Sparta’s favour, ushering in the period of decline that traditionally marks an end to Greece’s fabled ‘Golden Age’.
Conflict in Hellas
Among scholars and the general public, there is virtual unanimity that the great struggle between the Peloponnesians and the Athenians had its inception at the beginning of the campaigning season in the spring of 432 BC. This is Thucydides’ claim, and his authority in this particular has passed almost unchallenged.
There is, however, a tension between this claim and the Athenian historian’s further assertion that the war was a product of the fear generated at Lacedaemon (also called Sparta: the capital of the historic region of Laconia and the chief city of the Peloponnese) by the growth in Athenian power. After all, in 432, Athens’ ascent was old news. It was already in evidence nearly a half-century earlier, when the Persians made their withdrawal from the Balkans. In the immediate aftermath, in 478, a number of Sparta’s allies had expressed profound discomfort at Athens’ emergence as a major maritime power; and, in response, Lacedaemon had made a half-hearted effort to rein in the Athenians by persuading them to forgo rebuilding the walls around Athens that the Persians had torn down. Moreover, within a year thereafter, the Athenians had managed to oust the Lacedaemonians from the position they had hitherto held as the commanders of the Hellenic forces at sea, and to establish their own maritime hegemony in the Aegean. This had so upset the Spartans that, in the mid-470s, they had reportedly come quite close to launching a war against the Athenians.

That the Lacedaemonians seriously considered the option – and that, after a great deal of grumbling, they chose not to do so – is telling. In the aftermath of the Persian Wars, they faced a dilemma.
They were, to begin with, rich. Every Spartiate was, in effect, a gentleman – liberated from the need to till the soil. They not only had no need to expand, they had good reason to eschew further territorial aggrandisement. They controlled the southern Peloponnese – the Eurotas valley in Laconia and the Pamisos valley in Messenia, which, in tandem, constituted two-fifths of that great peninsula’s land-mass – reducing much of the population to the status of helots (intermediate in status between slaves and citizens), bound to the city and required to work its land for their Spartiate overlords. This subject population was a source of wealth, and of great danger as well. It is said to have outnumbered the population of masters by a ratio of 7:1 or more, and much of it constituted a nation in bondage – conscious of itself as a people, resentful, and restive.
Of necessity, then, the Spartans were homebodies. They could not afford to go far afield. Moreover, they needed allies. At home, they relied on the perÃoıkoı – the free, if subordinate, population that resided in the villages dotted around the two great river valleys. Abroad, they looked to their fellow Peloponnesians – apart, that is, from their ancient rivals the Argives, who lived in Argos, to the north-east. In the 6th century, they had organised what may have been the world’s first standing defensive alliance. In this way, they ousted tyrants and sponsored broad-based oligarchies throughout the peninsula; they suppressed, at least in some measure, local conflicts; and they looked after the security of the Peloponnese. In return, they expected support should there be a helot revolt.
This was a cosy arrangement. And, by and large, it worked. Had it not been for the appearance in and after the late 490s of the Mede – which is to say, the forces of Persia’s Great King – on their doorstep in the western Aegean, the Lacedaemonians would have remained fully satisfied with the settlement they had worked out.

The Persian menace, however, forced the Spartans to look further afield for support, and they were fortunate in finding in Athens an ally that proved capable, thanks to the income generated by a recent silver strike, of constructing and deploying a fleet of 200 triremes (galleys). The Lacedaemonians were a land-power. They relied on a host of heavy infantrymen called hoplites, famed for the effectiveness of their phalanx formation. At first, they may not have fully appreciated the importance of sea-power. The first fully amphibious force ever dispatched over any distance was the expedition that Darius of Persia had dispatched to Marathon, north-east of Athens, in 490; and it may not have been until ten years later, when Xerxes I sent an enormous armada against Hellas (as the Greeks called their homeland) by land and by sea, that it was brought home to the Spartans just how easily such a joint operation could confront them and pin them down on land, then outflank them by landing behind their lines a host of marines conveyed by sea.
Following victory at the Battle of Thermopylae in 480, Xerxes enjoyed a string of successes – including the capture and burning of Athens in September 480. But it was the decisive victory shortly thereafter for an Athenian-dominated Greek navy at the Battle of Salamis, and the subsequent Persian retreat, that proved a revelation for the Lacedaemonians. From this point, it was no longer possible to give the sea short-shrift. The dilemma they faced in and after 478 was straightforward. The Mede could not return to the Balkans if they did not control the sea. The logistical obstacles standing in the way of an invading army were simply too great. So, if the Spartans wanted to neutralise the ongoing Persian threat, they would either have to take to the sea themselves or find a proxy willing to do the dirty work for them. If, after much soul-searching, the Lacedaemonians were willing to acquiesce in the Athenians’ seizure of maritime hegemony over the Hellenes, it was because the latter were prepared to shoulder a burden that, the former feared, would be their undoing.

Conflict within Hellas
The Spartans’ decision to yield to the Athenians in this way was, at best, grudging. Pride and ambition argued against it, and there were those in their number who suspected from the outset that they were trading one threat for another. So it is not surprising that the Lacedaemonians chose to revisit the question when the Athenians appeared to have eliminated the prospect that the Mede would return, and began to take advantage of the maritime cities with which they were allied. Three events induced the Spartans to rethink. First, in c.468, the Athenians annihilated a great Persian fleet and a Persian army at Eurymedon on the south shore of Asia Minor. Then, they forged a peace of sorts with the Great King. Finally, they began encroaching on the rich possessions in the north-eastern region of Thrace, long owned by nearby Thasos.
This last act triggered a rebellion by the Thasians in 465 – followed, first, by a battle at sea in which the Athenians handily defeated the islanders’ fleet; and, then, by a siege. When the rebels appealed to Lacedaemon for help, the Spartans promised to come to their rescue; and in the spring of 464, they no doubt would have marched into the territory of Athens (the historical region known as Attica) with the forces of their Peloponnesian alliance, and compelled the Athenians to back off, had there not been a great earthquake late in the winter that halved the Spartiate population and set off (in Laconia and then in Messenia) a general helot revolt.
Initially, the Athenians were unaware of the pledge given to the Thasians. So, when called on to come to the aid of the Lacedaemonians, they dispatched a force of hoplites to help contain the revolt; and three years later, when the Spartans found it impossible to dislodge the remaining rebels from the redoubt they had built on Mount Ithome in Messenia, the Athenians sent to their assistance a small host of light-armed infantrymen skilled in siege warfare. It was in the midst of this campaign that Thasos fell, and we have reason to suspect that it was then that the Athenians learned of the Lacedaemonians’ pledge. For it was also in the midst of this campaign that the Athenians repudiated the alliance with Sparta, embraced the erstwhile Medizers (as those with Persian sympathies were called) of Argos and Thessaly, and cajoled the Megarians of western Attica into abandoning their connection with Lacedaemon and joining Athens instead. It was this that set off the first war between the Athenians and their allies and the Spartans and theirs.

For the most part, the fighting that took place in the 450s set Athens against the nearby island of Aegina in the Saronic Gulf and against the coastal cities in the Peloponnese, which were vulnerable to attack from the sea. The Lacedaemonians who survived the great earthquake and the general helot rebellion were, for the most part, nowhere to be seen. They were preoccupied instead with the rebel force conducting a guerrilla campaign from its seemingly unassailable stronghold on Mount Ithome; and the Athenians, who had garrisoned Megara at the entrance to the Peloponnese, were in a position to obstruct, if not block, egress from that great peninsula.
The Spartans bestirred themselves only once – when they got word that Aegina was on the verge of surrender and that the Athenians were well on their way to completing the fortifications, known as Long Walls, that would link Athens in the interior of Attica with the Athenian port in the Piraeus (thereby making the Athenian pólıs an island of sorts, impregnable against attack by land, and able to import food from abroad). They slipped northwards on boats across the Corinthian Gulf and marched into the region of Boeotia – where, at Tanagra in 457, they and their allies fought a two-day battle with the Athenians and their allies. For the Spartans, this contest ended with a tactical victory. They were left in control of the battlefield. But it was also for them a strategic defeat. The Peloponnesians returned to their peninsula. Then Aegina surrendered on terms, and the Athenians conquered Boeotia and completed their Long Walls.
Had the Athenians not become entangled in another war with the Mede – this one focused on an attempt to pry Egypt, with its riches, loose from the Persian empire – they might have succeeded step by step in dismembering Lacedaemon’s alliance, and in putting together a coalition of cities within the Peloponnese with which they and their Argive allies could challenge the Spartans on their home turf. As it worked out, however, there was a Persian resurgence; and, in 454, the Athenians and their allies lost something like 235 triremes and some 47,000 men in an ill-advised attempt to hold on to the Nile. This catastrophe, which reduced the adult male population of Athens by at least 20 per cent, occasioned a five-year truce between the Athenians and the Lacedaemonians, who rightly feared that the Mede would re-enter the Aegean. When the Athenians managed once again to annihilate the Persian fleet (this time at Cypriot Salamis, on the island’s east coast) and the five-year truce came to an end, the Lacedaemonians launched a lightning campaign in which they managed to outmanoeuvre and force them to disgorge everything they had gained in their forays along the Peloponnesian coastline.

This campaign, which took place in 446, was brilliantly staged. It began with a revolt in one corner of Boeotia and an ambush of the Athenian force sent to put it down. There followed a rebellion of the cities on the island of Euboea, just off the coast of Attica and Boeotia – the most valuable asset in what had by this time become an Athenian empire. Then, while the Athenians were preoccupied with Euboea, the Megarians rose up and slaughtered the Athenian garrison; and, when a substantial Athenian force marched into the Megarid and launched a counter-attack, Sparta’s Agiad king Pleistoanax (Sparta drew its kings from two royal houses, the Agiad and the Eurypontid) swept through that territory and into Attica with an army of Peloponnesians, cutting off that Athenian force from Athens. In response, the Athenians could have hunkered down behind their Long Walls. But, given the losses in manpower that they had suffered in Egypt, they could not afford to sacrifice the force isolated behind enemy lines in the Megarid – and so, on their behalf, Pericles (the statesman acclaimed by Thucydides as ‘the first citizen of Athens’) negotiated an armistice with Pleistoanax, requiring an Athenian withdrawal from the Peloponnese.
This arrangement formed the basis for a truce with a term of 30 years that brought armed conflict to an end. On the face of it, the provisions contained in the treaty would appear conducive to a lasting settlement. After all, it left the power supreme on land unchallenged within the Peloponnese, at peace with Argos, and allied with the Boeotians, who were now free; and it left the power supreme at sea in control of the Aegean. There was no obvious bone of contention left.
Some in Athens and in Lacedaemon may well have persuaded themselves that the dual hegemony established in the 470s, and now restored, would obviate future conflict. Others, from the outset, harboured grave doubts. They regarded the truce as nothing more than an interlude, and they were quickly proven right.
War becomes inevitable
The armistice negotiated by Pleistoanax and his principal adviser, the ephor (magistrate) Cleandridas, fell well short of what their compatriots wanted and expected. The war had confirmed to the Lacedaemonians that the fears they had entertained at the time of the Thasian revolt in 466 had been correct. Athens was, indeed, a menace – and the terms of the armistice did nothing to alleviate the danger. Moreover, in the aftermath of the agreement, the Spartans could do nothing to improve their situation. The leverage that they had possessed when Pleistoanax negotiated the armistice was no longer theirs. All that they could do was to ratify the terms agreed on, and take out their frustration on their Agiad king and his adviser. Their having accepted a sweetener from Pericles provided the excuse. Pleistoanax ended up in exile, and Cleandridas, who fled, was condemned to death in absentia.
There can be no doubt that the Athenians took notice of this development. Moreover, if anyone at Athens continued to entertain high hopes regarding the viability of the truce, those hopes were dashed in 440 when the Samians (from the Aegean island of Samos) revolted. Securing funding and mercenaries from the Persian satrap at Sardis, these hitherto stalwart allies of Athens appealed for help to the Lacedaemonians – who then called a meeting of their Peloponnesian League to discuss intervening in their support. That nothing came of this – that the Corinthians, the only city within the league that possessed a navy sizable enough to be capable of projecting power in the Aegean, scotched the proposal – the Athenians cannot have found reassuring. From that moment on, each of the two sides was lying in wait for an opportune moment to renew the war.

When a power dominant on land squares off against a power dominant at sea, it is difficult for either to land a knockout blow. The Spartans seized on the Samian revolt because it offered an opportunity. Samos had a substantial fleet. So did Corinth. Together, especially if they could attract support from Chios and the póleıs on Lesbos, which also possessed substantial fleets, they stood a chance against the Athenians. By the same token, the Athenians could not hope to eliminate Lacedaemon as a power unless they could themselves put together a coalition of Peloponnesian cities and defeat her on the battlefield.
Everyone understood this, and Pericles was no exception. Aware as he was that war was inevitable, he naturally saw it as his task to arrange that, when it came, the circumstances were conducive to an Athenian victory. It is in this light that we need to review the events leading up to Thucydides’ war.
It was Pericles who engineered the crisis, and he did so with an eye to breaking up the Peloponnesian League. Of course, he had nothing to do with the struggle that emerged over Epidamnus, a city-state in the Adriatic, between Corinth in the Peloponnese and Corcyra (modern Corfu) in the Ionian Sea. But when that maritime conflict erupted and, in duress, the Corcyraeans appealed to Athens for help, he seized the opportunity this afforded him. He saw to it that his compatriots made a defensive and not an offensive-and-defensive alliance with Corcyra, that they dispatched an exceedingly modest force to help that community defend herself, and that the commanders of that force were instructed to join in battle if and only if it looked as if Corcyra would otherwise fall. His aim was to enrage the Corinthians, who harboured bitter memories of the suffering inflicted on them in the previous war, while assuring the Spartans that Athens, which had no desire for armed conflict, wanted only to maintain the existing balance of power. Later, when he persuaded his compatriots to impose an embargo on Megara as punishment for her participation on the Corinthian side in the pertinent battle, Pericles made sure that Athens’ conduct was not a formal breach of the truce with Lacedaemon; and, when the Spartans objected to the embargo, he suggested that the dispute be submitted to arbitration – precisely as stipulated in the truce.

All of this the Athenian statesman did as a matter of calculation. He knew that Megara was a sore point for the Corinthians. In 461, the Megarians had allied with Athens as a consequence of a territorial dispute with Corinth, and it was this that had occasioned the pummelling that the Athenians had administered to Corinth. Moreover, if the Athenians could get away with the imposition of an embargo on Megara, they could do the same to Corinth, which was a mercantile city dependent on maritime trade. Pericles was also aware that Lacedaemonians were annoyed with the Corinthians. Epidamnus was no concern of theirs. And he suspected that, in such a situation, the Spartans would be reluctant to break the oaths they had taken in 446 when they ratified the truce. Moreover, he expected that a Lacedaemonian refusal to fight on the Corinthians’ behalf on this occasion would cause them to bolt from the Peloponnesian League in a great rage, and to take other cities with them – as they had, in fact, threatened to do.
If, on the other hand, the Spartans chose to fight, Pericles knew that the Long Walls would render their efforts ineffective. Before long, he presumed, they would tire of the war and sue for peace – which would then embitter the Corinthians and induce them to make good on their threat. This, in turn, would open the door for the Athenians to draw the Argives back into the fray and launch against Lacedaemon a coalition war on land within the Peloponnese.
Thucydides’ war should therefore be seen as an inevitable renewal of the struggle that had begun in the late 460s, when the Athenians learned that the Spartans had pledged to come to the aid of their rebellious Thasian allies. This is, after all, what Pericles and his compatriots believed. So, at least, we are told by the great historian. •