The Peloponnesian War: A Clash of Titans

Barely fifty years after the Greeks united to repel the Persian invasion under Xerxes,
culminating in the glorious victory at Plataea, a deep division grew between the two great
city-states of Athens and Sparta. This rivalry would eventually ignite the flames of war,
resulting in unprecedented destruction and bloodshed. The Peloponnesian War would bring
about the fall of one great power and the end of their golden age.

Thucydides, the ancient historian, described the situation in stark terms in his History of the Peloponnesian War: “It was the rise of Athens and the fear that this inspired in Sparta that
made war inevitable.” This insight captures the essence of a geopolitical reality that has
echoed down the centuries—when a rising power challenges an established one, conflict
often becomes unavoidable.

The Peloponnesian War, though fought more than two millennia ago, offers timeless lessons
about the dynamics of power, alliance, and conflict. This blog will take you through the
intricacies of the Peloponnesian War, exploring how two erstwhile allies became bitter
enemies and the devastating toll it took on the Greek world.

The Delian League: Athens’ Rise to Power

In the aftermath of the Persian withdrawal from Greece following the defeat at Plataea, the
Greek city-states were eager to prevent any future threats to their freedom. To safeguard
against this, Athens, leveraging its newfound power and naval dominance, led the creation
of the Delian League in 478 BC. The League was conceived as a defensive alliance,
ostensibly aimed at repelling any future Persian incursions.

Representatives from various city-states convened on the sacred island of Delos to formalize
the league. Delos, chosen as the site for the alliance’s treasury, was a neutral territory with
significant religious importance—it was believed to be the birthplace of the twin gods Apollo
and Artemis. Notable members of the League included powerful Ionian cities such as
Ephesus, Miletus, Chios, and Samos, who shared linguistic and cultural ties with Athens.
Other Greek states, including Aeolians and Doric Greeks, joined the alliance, and all pledged
to contribute resources for mutual defense against Persia.

Although the League began as a collective effort, it quickly became dominated by Athens.
The city-state, possessing the strongest navy in Greece, exerted its authority over the
League with increasing assertiveness. The League’s mutual defense pact gradually
morphed into an instrument of Athenian imperialism. Initially, Athens maintained its role as a leader, but it was clear that the city-state was pushing the boundaries of the League’s original purpose. In 470 BC, the island of Naxos, frustrated by Athens’ heavy-handed demands and increasing tribute payments, sought to withdraw from the League. In response, Athens dispatched an expeditionary force to Naxos, defeated the island’s forces, and forced them to remain part of the League, imposing even stricter tribute and military obligations.

The situation escalated in 465 BC, when Thasos, another member of the League, attempted
to secede. After a prolonged military confrontation, Athens once again proved its dominance,
capturing the island’s fleet and further consolidating its control. These examples set a clear
precedent: once a city-state joined the League, withdrawal was not an option, and Athens
would use military force to enforce its will.

In 454 BC, under the leadership of Pericles, Athens made a crucial decision that would
further cement its dominance. The League’s treasury, originally stored on Delos, was moved
to Athens. The move, purportedly for security reasons, was a clear signal of Athens’ intent to
control the financial and military resources of the League. This allowed Athens to fund grand
architectural projects, including the construction of the Parthenon, and to strengthen its navy
even further. At this point, the Delian League ceased to function as a mutual defense pact
and effectively became an Athenian empire. Membership was no longer voluntary; those
who resisted were met with force.

Some city-states were forced to adopt Athenian-style democracy, which was imposed by
garrisons of Athenian troops. These political changes spread across the Aegean world,
creating a more homogenized and Athenian-centric Greek world, but one that also
engendered growing resentment among the League’s smaller members. This shift in power
greatly alarmed Sparta and the Peloponnesian League, which saw Athens’ expansionist
policies as a direct challenge to their own influence in Greece.

The Peloponnesian League: Sparta’s Response to Athens’ Growing Power

While Athens expanded its influence over the Aegean world, Sparta had already established
itself as the dominant military power in the Peloponnesus. Sparta’s military prowess, built
around the discipline of its hoplite soldiers and its highly structured society, was formidable.
The Peloponnesian League, a coalition of city-states led by Sparta, was formed as early as
the 6th century BC to protect the interests of its members in the Peloponnesus.

The core members of the Peloponnesian League included powerful states like Corinth, Elis,
Tegea, and later, Thebes. These cities shared a similar oligarchic political structure, which
stood in stark contrast to the democratic institutions that flourished in Athens. While Sparta’s
government was ruled by a small group of Ephors, a council of five officials who wielded
significant power, the Peloponnesian League had no centralized treasury, and its members
were expected to contribute soldiers and resources independently.

The Peloponnesian League had long been the dominant force in Greece, but as Athens
grew in power, tensions began to rise. The fear of Athens’ increasing influence over the
Greek world led to growing hostility between the two coalitions. The Peloponnesian League
began to consolidate its power in response to what it saw as Athenian overreach.
Despite its military strength, the Peloponnesian League was politically fragmented. Spartan
hegemony, while formidable, was not always enough to maintain unity within the League.
The growing rivalry between Sparta and Athens had profound implications for the balance of
power in the Greek world, and it set the stage for the eventual outbreak of war.

The Growing Hostility: Flashpoints Leading to War

Several key events contributed to the deterioration of relations between Athens and Sparta.
The fear of Athenian imperialism grew as Athens solidified its control over the League, and
several key flashpoints provided the immediate causes for war. The first major incident came in 433 BC with the Corcyra Incident. Corcyra, a colony of Corinth, broke away from its mother city to become an independent naval power. Corinth, fearing the loss of influence in the region, sought to reassert its control over Corcyra, and the two states clashed. Corcyra, outmatched by Corinth’s military might, turned to Athens for assistance. In return, the Athenians agreed to send a fleet of ten triremes to support their new allies, a move that angered Corinth. This intervention brought Athens into direct conflict with Corinth, and Corinth, in turn, sought Spartan support.

This diplomatic crisis only worsened tensions. In 432 BC, another incident occurred involving
the city of Potidaea. Potidaea was a Corinthian colony but was also a member of the Delian
League. Athens, fearing that Potidaea might become disloyal, demanded that it sever its ties
with Corinth, dismantle its fortifications, and accept an Athenian garrison. Potidaea resisted,
and Athens responded by sending an army to lay siege to the city. Corinth, again angered by
Athenian aggression, sent reinforcements to Potidaea, and the situation rapidly escalated.
By this point, Sparta was becoming increasingly concerned about the rise of Athens and its
growing influence over the Greek world. Athens, meanwhile, was becoming more assertive
in its foreign policy, and its ability to project power through its navy only fueled Sparta’s fears.
The Peloponnesian League, already concerned about Athenian imperialism, began to seek
an opportunity for open conflict.

The Megarian Decree: The Final Provocation

The final straw came in 432 BC with the Megarian Decree. Megara, a city-state allied with
the Peloponnesian League, relied heavily on trade to sustain its economy. Athens, alleging
that Megara had seized sacred land belonging to Eleusis, enacted a trade embargo that
prevented Megara from accessing Athenian ports. This act of economic warfare inflicted
severe hardship on Megara, and the city appealed to Corinth and Sparta for assistance.
Sparta, angered by the embargo and eager to curb Athenian power, issued an ultimatum to
Athens: either relinquish control over the other Greek states or face war. Athens, feeling
confident in its naval superiority and unwilling to cede any ground, refused. Sparta, backed
by Corinth and the Peloponnesian League, declared war, marking the official beginning of
the Peloponnesian War in 431 BC.

The Peloponnesian War’s Origins and Immediate Effects

The Peloponnesian War was not simply the result of a series of isolated incidents, but the
culmination of decades of tension between two rising powers. Athens, having shifted from a
mutual defensive alliance to an imperial power, provoked the growing fear and resentment of Sparta and its allies. Sparta, for its part, sought to preserve its hegemonic role in Greece and
resist the rise of Athenian dominance.

What began as a war to protect the balance of power in Greece soon became a protracted
and devastating conflict that would shape the course of Greek history for years to come. The
war would not only bring about massive military and economic devastation but would also
alter the very nature of Greek society. The consequences of the Peloponnesian War would
resonate through Greek political thought, as well as the legacy of democracy, empire, and
military strategy.

The Phases of the Peloponnesian War: The Evolution of the Conflict

The Peloponnesian War was not a single, continuous battle but a series of interconnected
conflicts, alliances, and shifting strategies. The war unfolded in three distinct phases, each
characterized by its own unique set of battles, political developments, and military tactics.
These phases are often referred to as the “Archidamian War”, the “Sicilian Expedition”, and
the “Ionian or Decelean War”.

The Archidamian War (431–421 BC)

The first phase of the Peloponnesian War, known as the “Archidamian War”, was marked by
a series of annual invasions and battles, but it was largely defined by an intense stalemate
between Athens and Sparta. The conflict began in 431 BC, immediately after Sparta
declared war, and initially, it seemed as if Sparta’s military might would dominate.
The war’s initial phase was characterized by a Spartan strategy that capitalized on their
superior land forces. Led by King Archidamus II, the Spartans launched a series of invasions
into the Athenian territory. Every year, the Spartan army would march into the fertile plains of
Attica, devastating the land and burning crops. This strategy was designed to cripple the
Athenian economy and force Athens to come to the negotiating table. However, Athens, with
its powerful navy and well-fortified walls, was able to withstand these land invasions without
losing its ability to project power across the Aegean.

Under the leadership of Pericles, Athens adopted a strategy that played to its strengths: a
defensive approach that relied on its superior naval capabilities and the security provided by
its long walls. These walls connected the city of Athens to its port, Piraeus, allowing the
Athenians to receive supplies and reinforcements from their allies across the Aegean without
having to venture outside their walls.

Pericles’ Strategy: A War of Attrition

Pericles, one of the greatest Athenian statesmen, recognized that Athens could not directly
engage Sparta on the land, where the Spartan hoplite soldiers were unparalleled. Instead,
Pericles devised a strategy based on attrition, a war of wearing down the enemy. He
proposed that Athens should avoid large-scale battles with the Peloponnesians, and instead
focus on naval raids and using their navy to disrupt Spartan trade and communications.
Athens also used its maritime power to maintain control over the Aegean Sea and continue
its imperial dominance over the Delian League.

While the strategy was initially successful, the war began to take its toll. The Athenians were
forced to endure the constant Spartan invasions and the accompanying devastation of their
countryside. However, they managed to preserve their vital naval superiority and maintain
economic activity through maritime trade. Sparta, on the other hand, struggled to break
through Athens’ defensive walls and was unable to gain a decisive victory.

The Plague of Athens: A Turning Point in the Peloponnesian War

The early years of the war were further complicated by the “Plague of Athens”, which struck
the city in 430 BC. The plague, which is thought to have been a form of typhus or possibly a
form of bubonic plague, decimated the Athenian population. It is estimated that between
one-quarter and one-third of the population died, including the great leader Pericles. The
loss of such a prominent figure weakened Athenian leadership, and the city’s morale
suffered greatly.

Pericles’ death in 429 BC led to a power vacuum and political instability in Athens. His death,
coupled with the ongoing strain of the war and the impact of the plague, led to a series of
political changes in Athens, with more aggressive and sometimes reckless leaders coming to
power. The plague’s effect on Athens was not just demographic but psychological—it deeply
affected the city’s morale, and Thucydides famously described how the moral fabric of
society unraveled as the plague spread. Despite this tragedy, Athens continued to maintain its navy and resisted Spartan efforts to force a peace settlement. The war took on a more protracted and brutal nature, as both sides adapted to the increasingly costly stalemate.

The Peace of Nicias: A Fragile Ceasefire (421 BC)

After more than a decade of inconclusive fighting, both Athens and Sparta were weary of the
war. The “Peace of Nicias”, signed in 421 BC, marked the end of the first phase of the war
and represented an uneasy truce between the two powers. Named after the Athenian
general Nicias, who had played a central role in negotiating the peace, the agreement was
intended to last for fifty years. Under the terms of the peace, both sides agreed to halt
hostilities and return any conquered territory to its rightful owners.

However, the Peace of Nicias was fragile from the outset. Both sides harbored suspicions
that the other was using the truce to strengthen their position. The terms were never fully
implemented, and the peace did not resolve the underlying issues of Athenian imperialism
and Spartan fears of Athenian dominance. Tensions remained high, and the fragile peace
would soon unravel.

Phase 2: The Sicilian Expedition (415–413 BC)

The second phase of the Peloponnesian War, which is often referred to as the “Sicilian
Expedition”, marked a major turning point in the conflict. Athens, under the leadership of
Alcibiades, an ambitious and charismatic leader, decided to undertake an ambitious military
campaign to Sicily. The goal of this expedition was to capture the strategically important city of Syracuse, which could potentially weaken Sparta’s position and provide Athens with new
sources of wealth and resources.

The campaign was doomed from the start due to a combination of overconfidence, poor
planning, and internal political instability in Athens. Alcibiades, who had originally
spearheaded the expedition, was accused of sacrilege and fled to Sparta, where he
betrayed Athens and offered his services to the enemy.

The Athenian fleet, although large and well-equipped, suffered from a lack of coordination
and leadership after Alcibiades’ departure. The Syracusans, supported by Spartan advisors
and reinforcements, managed to decisively defeat the Athenian fleet in a series of battles.
The failure of the Sicilian Expedition was one of the most significant setbacks in Athenian
history. Thousands of Athenian soldiers were killed or captured, and the prestige of Athens
was severely damaged.

This defeat marked the beginning of the decline of Athenian power. The resources required
for the campaign drained the Athenian treasury, and the loss of so many soldiers and ships
dealt a devastating blow to the city-state’s military capability.

Phase 3: The Ionian or Decelean War (413–404 BC)

The final phase of the Peloponnesian War, known as the “Ionian or Decelean War”, was
defined by a shift in strategy and the eventual downfall of Athens. After the failure of the
Sicilian Expedition, Athens faced increasing internal divisions and external pressures.
One of the most significant changes during this phase was the establishment of the Spartan
base at Decelea in the heart of Attica. This strategic outpost allowed Sparta to conduct raids
on Athenian territory and put further strain on Athens’ resources. The Spartans were also
able to receive financial support from the Persian Empire, which had grown wary of Athenian
power. Persian gold flowed into Spartan coffers, allowing them to build a powerful fleet
capable of challenging Athens at sea.

In response, Athens attempted to continue its naval operations, but it became increasingly
difficult to maintain its once-powerful fleet without the resources it had lost in Sicily. Tensions
within Athens deepened, and political instability took its toll. At the same time, the support of
the Persian Empire gave Sparta the means to match Athens on the seas, where the latter
had once dominated.

The “Battle of Aegospotami” in 405 BC, a decisive naval engagement, marked the end of
Athens’ supremacy at sea. The Spartan fleet, now reinforced by Persian financial backing,
decisively defeated the Athenians, capturing most of their fleet and effectively cutting off
Athens from its crucial supply lines. This defeat was catastrophic for Athens, and shortly
thereafter, the city was forced to surrender.

The End of the Peloponnesian War: Athens’ Fall and Sparta’s Decline

The defeat at Aegospotami led directly to the collapse of Athens. In 404 BC, Athens was
forced to surrender to Sparta, bringing the Peloponnesian War to a close. The Spartans,
having emerged victorious, imposed harsh terms on Athens, including the dismantling of its
walls and the establishment of an oligarchic government, known as the “Thirty Tyrants”, who
were sympathetic to Spartan interests.

Despite their victory, Sparta’s triumph was short-lived. The city-state had been drained of
resources during the war, and the continued instability within Greece would soon set the
stage for future conflicts. Athens, though severely weakened, would eventually recover, and
its democratic ideals would reassert themselves under the leadership of figures like
Alcibiades, who had earlier played a role in the downfall of the city.
The Peloponnesian War had lasting consequences for the Greek world. It weakened the
city-states of Greece, and although Sparta was the victor, it was ultimately unable to
maintain the dominance it had sought. In the years following the war, Thebes and eventually
Macedonia would rise to prominence, signaling the end of the era of independent Greek city-states. If you’re interested in more Ancient Greek history, check out our blog page for more details.