The Peloponnesian War (431–404 BCE) stands as a seminal conflict in ancient Greek history, pitting the maritime power of Athens against the land-based might of Sparta. This article would, therefore, be intended to discuss the complex interplay of ever-changing alliances, along with the strategic motivations and overall balance of power characteristic of this long conflict.
Rimmo Loyi Lego explains.
The destruction of the Athenian army at Syracuse. By John Steeple Davis.
Introduction & Brief Background
The Peloponnesian War, which took place from 431 to 404 BCE, is in many ways exemplary of the very complex play of alliances, power dynamics, and strategic imperatives characterizing ancient Greece. First, it was a struggle expressing in its roots the very principles of structural realism that govern inter-state relations according to which, in an international system characterized by anarchy, only accumulation of power through forming alliances could reach security. To understand why war was almost an inevitable result, one has to look at the anarchic political landscape of the Greek city-state system. Unlike the centralized empires of Persia or Egypt, Greece was a fragmented collection of independent poleis, each with its own government, military, and strategic interests. There was no overriding authority to moderate disputes or impose order on this Greek world, making it an excellent example of what structural realism would identify as an anarchic international system.
Power, in this very decentralized system, became the final guarantor of security, whereas alliances were the mechanisms for survival—not instruments of collective peace. After the Persian Wars (499–449 BCE), two great powers with their respective coalitions began to look towards securing their respective interests. Athens, by its supremacy in naval affairs, transformed the voluntary defensive alliance against Persia into something of an Athenian-controlled empire through the Delian League. This centralization of power, allied with the use of tribute from allied states to fund its expansionist policies, caused resentment among the Greek city-states that had initially joined the league for mutual security.
On the other hand, Sparta, as the leader of the Peloponnesian League, led a coalition of land-based, conservative, oligarchic states opposed to Athenian imperial ambitions. Unlike the relatively open democratic society of Athens, Sparta was militarized and deeply invested in the maintenance of internal stability, especially given its dependence on an enslaved population of helots. Athenian interference in the affairs of Peloponnesian League members and its economic sanctions against key Spartan allies like Corinth and Megara fanned the flames of ill-will.
The structural realist perspective postulates that since Greece had no central authority, its system worked through the logic of self-help where no state could be completely secure about the intentions of another. This change in the balance of power, because of the rise of Athens, began to spur a security dilemma whereby both Athens and Sparta felt threatened by what each was doing for its own defense. The fear of encirclement by Athenian influence, and the anxiety in Athens over possible Spartan intervention in its empire, fed a cycle of hostilities. By the time war broke out in 431 BCE, diplomatic mechanisms had failed, and neither side was willing to give up strategic ground without risking a loss of prestige and power. The Peloponnesian War, then, was not a struggle of two ideologies—democracy versus oligarchy—but rather an structural necessity, given the logic of an anarchic system where competing hegemons cannot co-exist peacefully.
Alliances in the Peloponnesian War
Because of the Persian Wars, Greek city-states understood the need to develop alliances to safeguard themselves from future attacks. This gave birth to the Delian League and the Peloponnesian League.
The Delian League was created in 478 BCE, with an Athenian leadership base and was designed to be a coalition of states to continue fighting against Persia and free the Greek cities which, at that time, were under the Persian rule. Every free city-state trained sails or gave money to aid the league's primary aim of freeing the city-states and retrieving the ships. The league was based on the sacred island of Delos, so every city gave tribute. Gradually, the league shifted in aim when Athens assumed control and the resources aided imperial initiatives. Member states were thus used to enhance Athenian power.
The Peloponnesian League, headed by Sparta, was an alliance based on collective defense and the preservation of the order. In contrast with the formally established structures of the Delian League, the Peloponnesian League was less rigid, with Sparta taking political supremacy among its allies. Primarily, this coalition included the city-states from the Peloponnese region seeking to inhibit Athenian dominance and retain autonomy.
From a structural realist perspective, these alliances can thereby be viewed as strategic responses to the anarchic international system. Athens and Sparta, as principal actors, sought to enhance their security and project power through these coalitions, thereby attempting to mitigate the uncertainties inherent in a decentralized political landscape.
Motivations of Athens and Sparta
Although both city-states were substantially important in Greece, they were directed by motivations quite opposite to one another founded on the various political systems, economic structure, and attitudes of their citizenry.
Athens, being a burgeoning maritime power, wished to expand its influence and protect interests on the economic front. This ambition was exemplified firstly by the formation of the Delian League and then by its evolution into an Athenian Empire. A democratic-style government in the city advanced a culture of dynamic thinking and self-assertiveness that propelled the city toward the idea of empire. Control over critical sea routes and a network of trade was paramount in the suppression of dissent among its subordinate states. The Athenian leadership, under Pericles' authority, visualized Athenian supremacy both culturally and politically. Pericles' Funeral Oration, as presented in Thucydides' writings, praised the values of Athenian democracy, its imperial design, and is a reflection of a city-state quite confident in its destiny. On the contrary, Sparta held itself back by conservatism, assuming immediate preservation of traditional interests and the preservation of an existing balance of power. The expansion of Athenian influence was perceived by Sparta as a shortcut to threaten Spartan hegemony and thus disrupt its pro-Allied alliance. The anxiety of encirclement and the potential weakening of the entire Peloponnesian League compelled the Spartans to contemplate going to war. Additionally, several speeches made in the Spartan Assembly by Thucydides gave light to incipient worries about the Athenians and how they could act if challenged. In brief, both states realized their choices as a deliberate action under the lens of a structural realist approach. Athens wanted to maximize its own power for the security of its state against economic threats.
War as a Balance of Power Mechanism
The Peloponnesian War may thus be interpreted, in a general sense, with the balance of power theory—a central tenet of structural realism. The balance of power theory posits that states will act to prevent any one actor from achieving hegemony, thereby maintaining an equilibrium that ensures their survival.
The rapid rise of Athens disturbed the previous balance and made it a bipolar system with two hegemonic powers. This change brought about a security dilemma where the defensive actions of one state were perceived as offensive threats by the other. In the eyes of Sparta, the fortifications and naval expansions of Athens were preparations for aggression, while for Athens, the mobilizations of Sparta were signals of an imminent invasion.
The proximate cause of the war was a dispute between Corinth and Corcyra, the intervention of Athens on behalf of Corcyra bringing about open hostilities between Athens and Corinth. The follow-up Athenian decree against Megara, better known as the Megarian Decree, acted as further aggrandizement. An ultimatum sent by Sparta to Athens, asking for the abrogation of the decree and the removal of economic sanctions on Megara, was brusquely refused. The failure of said diplomatic efforts finally led to the Spartan declaration of war in 431 BCE, and hence the long conflict started. The war that followed could therefore be an attempt on the part of Sparta and its allies to restore the balance of power by reining in the Athenian expansion and reasserting their own influence within the Greek world.
Security Dilemmas and the Escalation of Conflict
The Peloponnesian War is thus a stellar example of what would constitute a security dilemma: a state's actions to increase its own security decrease the security of others, which in turn leads to an escalatory dynamic.
To Sparta and her allies, such imperial policies by Athens—which included the enforcement of the Megarian Decree—came to be seen as direct threats to their economic and political interests. Equally, Athens viewed the mobilization of Sparta and her support for dissident elements within the Athenian empire as aggressive moves designed to destroy its authority.
This mutual suspicion and the lack of mechanisms to dispel the perceived threats led to an intensification of hostilities. The view from structural realism is that, in the absence of the Leviathan that characterizes the anarchic structure of the international system, there are no means for states but to resort to self-help. One of the important factors for the perpetuation of the war was the security dilemma in which both Athens and Sparta were trapped: neither could show weakness nor could either side give the other any strategic advantages.
The Role of Persia: Strategic Interventions and Realpolitik
Perhaps one of the most significant, yet sometimes underappreciated or simply not appreciated, aspects of the Peloponnesian War would be the role played by Persia. This war is generally remembered as a struggle among Greeks, but the Persian Empire did actively intervene in its course by choosing specific instances of intervention, giving financial aid to Sparta, and maneuvering diplomatically. In terms of the structural realist view, Persia's policy can be accounted for in that great powers play on the rivalries of emerging powers in a manner that allows them to conserve their influence without engaging in a frontal clash.
Thus, during the early years of the War, Persia kept mostly out of it, preferring to watch from the sidelines. But as the war dragged on and both Athens and Sparta began to suffer economic and military attrition, Persia saw its chance to reassert its authority over the Greek world, particularly in Ionia, which had been a contested region since the Persian Wars. The turning point came in the later years of the war when Sparta, realizing it could not hope to compete with Athens in terms of financial resources and naval power, turned to Persia for support.
In 412 BCE, Sparta negotiated the Treaty of Miletus with the Persian satrap Tissaphernes whereby Persia would provide financial aid to the Spartan fleet in return for Spartan recognition of Persian control over the Ionian cities—a classic realist strategy whereby states put survival and strategic advantage above ideological or historical scores. Sparta, though having fought on the side of Persia during the earlier Greco-Persian Wars, now joined its erstwhile enemy to conveniently help bring pressure on Athens—such intervention made all the difference.
This was possible only through the gold of Persia, which enabled Sparta to build a formidable navy and thereby ultimately conquer Athens at the Battle of Aegospotami in 405 BCE, in which the entire Athenian fleet was annihilated. This last blow led to the siege and surrender of Athens in 404 BCE. The ability of an exogenous actor, Persia, to manipulate and influence the war between the Greek city-states lends weight to the structural realist notion that weak states—here, Athens and Sparta relative to Persia—are always at the mercy of a stronger power's strategic calculations. Persia played Athens and Sparta rather perfectly against each other, making sure that none of them ever rose as an unrivaled hegemon in the Greek world.
Conclusion: A Structural Realist Interpretation of the Peloponnesian War
The Peloponnesian War was the inevitable consequence of the rise of Athens to pre-eminence that fundamentally disrupted the existing balance of the Greek world. According to structural realism—especially the variant offered by Kenneth Waltz and John Mearsheimer—the anarchic character of the international system compels states to seek power for survival, which entails conflict when a rising power challenges the dominance of an established hegemon. Sparta, the paramount land power, saw Athenian expansion as an existential threat to its very survival; it found itself in a security dilemma with the other great power, each escalating its military preparedness and making war all but inevitable. The war was not a matter of ideology but a structural necessity to restore equilibrium in the Greek world, proving the realist assertion that power struggles, rather than moral or ideological factors, dictate international relations.
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