Sparta and its allies won the Peloponnesian War, which ended in 404 BCE with the defeat and surrender of Athens. The victory was not achieved through one isolated battle but through a prolonged process in which Spartan strategy, Athenian losses, Persian financial support, changing alliances and naval developments gradually altered the balance of power. Athens had remained resilient for decades because of its powerful fleet, fortified position and financial resources derived from its empire.
The decisive phase occurred during the later stages of the war when Sparta developed a more effective naval capability and obtained Persian assistance. The Spartan victory ended Athens's maritime empire, weakened its military position and temporarily established Sparta as the dominant Greek power. The outcome therefore represented a major transformation of the Greek political system rather than merely the defeat of one army.
Sparta's victory was particularly significant because it had traditionally been stronger on land than at sea. During the later war, however, Spartan commanders and allies developed naval forces capable of challenging Athens in the Aegean. Persian support became crucial because Persian financial resources helped Sparta pay crews and construct or maintain fleets. Cyrus the Younger, a Persian prince and satrap, provided important assistance to the Spartan commander Lysander.
Persian involvement reflected Persian strategic interests in weakening Athens rather than simple ideological support for Sparta. The Persian Empire had long competed with Greek powers over influence in the eastern Aegean, and the weakening of Athens offered strategic advantages. Spartan victory was therefore partly dependent upon an international dimension that extended beyond the Greek city states themselves.
The Sicilian Expedition of 415 to 413 BCE was a major turning point in the war. Athens sent a large expeditionary force to Sicily, primarily against Syracuse, and the campaign ended with the destruction or capture of the Athenian army and fleet. The scale of the losses severely reduced Athens's military capacity and weakened confidence in its leadership. Syracuse survived and became an important contributor to the anti Athenian effort. Following the disaster, Sparta intensified pressure on Athens, and the occupation of Decelea in Attica disrupted agriculture and communications. The Athenian empire nevertheless continued to provide resources, demonstrating that the Sicilian disaster was a turning point rather than an immediate end to the war.
The later phase of the conflict became a struggle for control of the Aegean and its vital maritime routes. Athens rebuilt fleets and achieved several naval successes, including victories at Cyzicus in 410 BCE. These successes demonstrate why the final outcome was not predetermined after Sicily. Athens still possessed substantial financial and naval resources and was capable of recovering from major setbacks. However, internal political instability also weakened its ability to maintain consistent strategy.
The oligarchic revolution of 411 BCE briefly replaced the democratic government, followed by political restoration. Such constitutional conflict occurred while Athens was simultaneously conducting a major war. The continuing strain of military expenditure, losses and political disagreement reduced the stability required for a sustained strategic recovery.
Lysander played a crucial role in the final Spartan victory. He developed close relations with Cyrus the Younger and used Persian financial assistance to maintain Spartan crews and naval forces. In 405 BCE, the Spartan fleet confronted the Athenian fleet at Aegospotami on the Hellespont. Lysander captured most of the Athenian fleet after exploiting the Athenians' vulnerable deployment. The loss was catastrophic because Athens depended upon maritime access for food and other supplies. After Aegospotami, Sparta and its allies besieged Athens. The city eventually surrendered in 404 BCE. The surrender terms included the destruction of the Long Walls and the reduction of the Athenian fleet, marking the collapse of the city's imperial system.
The immediate political consequences of Spartan victory were substantial. Athens lost its empire and much of its naval power, while Sparta became the leading power among the Greek city states. A Spartan backed oligarchic regime known as the Thirty Tyrants was established at Athens, although it was later overthrown and democracy restored in 403 BCE. The Spartan victory therefore did not permanently eliminate Athenian political institutions. It also did not produce stable Spartan domination.
Sparta soon faced resistance from other Greek powers, and its attempt to maintain hegemony generated new conflicts. The victory was consequently real and decisive in the context of the Peloponnesian War, but it did not establish an enduring Spartan empire comparable in longevity to the Athenian maritime system.
The outcome of the war also had wider consequences for Greece. Large numbers of soldiers and civilians had died, cities had suffered destruction and political systems had been destabilised. Persia increased its influence over Greek affairs, while Sparta's supremacy encouraged further competition. The Corinthian War began only a few years later, and Sparta's position was challenged by Athens, Corinth, Thebes and other states. Thebes eventually defeated Sparta at Leuctra in 371 BCE, ending the period of Spartan military predominance. The fourth century BCE therefore demonstrates that the Peloponnesian War did not create a permanent victor in Greek politics. Instead, it accelerated a cycle of shifting hegemonies that eventually contributed to the rise of Macedon under Philip II.
The answer to the question of who won is therefore straightforward at the level of the war itself: Sparta and its allies defeated Athens and its alliance system in 404 BCE. The historical significance of the victory is more complex. Sparta gained temporary hegemony, Athens lost its empire and naval dominance, and the Greek balance of power changed dramatically. Yet Sparta did not permanently dominate Greece, and Athens recovered its political independence and eventually rebuilt significant influence.
The war also left all major Greek communities weakened relative to the Macedonian kingdom that later became the dominant power under Philip II and Alexander the Great. The Spartan victory should therefore be distinguished from the much broader question of which Greek state ultimately achieved long term political dominance, because the Peloponnesian War itself ended with Spartan success even though the subsequent history of Greece followed a different trajectory.
