Peloponnesian War: Athens vs. Sparta, Causes, Battles & Historical Impact Explained

The Peloponnesian War—a war between a naval empire, Athens, and a land force, Sparta—had its origins in the continual internecine wars of the Greek poleis. The war between the two great powers could be seen as a struggle lasting fifty-five years, divided into three phases. The first lasted fifteen years, from 460-445, when the two fought for control of the mainland until Athens was defeated and entered into the Thirty Years Peace with Sparta. The second and third phases became known collectively as the Peloponnesian War, but this term was never used by the historian Thucydides.

The second phase, which occurred after nearly half the peace had been observed, ran from 431 to 421 and is commonly called the Archidamian War, after its Spartan king, and concluded with the Peace of Nicias, named for an Athenian statesman. The final phase, from 420 to 404, witnessed the Athenian defeat. Unlike other events, the Peloponnesian War had a contemporary author, Thucydides, recording the events. Although an Athenian, he still presented the events in as unbiased a way as he could, given his background.

As Athens grew in power and expanded in the eastern Mediterranean, its control of the economic conditions in Greece increased. This in turn brought it into conflict with other major powers—most notably Corinth, an ally of Sparta. Corinth had an extensive trade network around its colonies that brought it into conflict with Athens since some of these colonies were part of the Athenian Empire. Other Corinthian colonies were opposed to their mother city, some of whom either allied themselves with Athens or remained neutral. The two daughter cities of Corinth that forced the two major powers into conflict were Corcyra and Potidaea.

There were other reasons for the war, the most crucial being Sparta’s fear that Athens would ultimately dominate all of Greece, and thus its own power would be diminished. After Athens continued its growth, Sparta was content to retreat within the Peloponnese and had traditionally sought to control only the Peloponnese; Corinth, being the only Peloponnese power with extensive trade arrangements, complained to Sparta of Athens hampering its power and connections. Sparta did not feel inclined to act, in part because it feared of moving beyond the Peloponnese and potentially allow the helots to rebel.

The first incident to spark the war came with the conflict of Corcyra against its mother city of Corinth. Athens could not allow the third-largest fleet, Corcyra, becoming part of the second-largest fleet, Corinth, thereby supplanting the largest one, Athens. When Athens joined with Corcyra in a defensive pact and, through a convenient event in 433, allowed Athens to best Corinth without it being an offensive act; Corinth complained to Sparta, which did not act even though it was annoyed. The next event concerned the Corinthian colony of Potidaea, which was part of the Athenian Empire. Potidaea received its magistrates from Corinth, and after the war took place between Corcyra and Corinth with Athens being involved, Athens demanded that Potidaea stop receiving its magistrates from Corinth and tear down its walls.

In the region of the Chalcidice, other cities that belonged to the Athenian Empire were encouraged to raise a revolt against Athens by the king of Macedonia. In addition, Potidaea was promised aid from Sparta if attacked, even by Athens. The Corinthians arrived with some forces and were bested by the Athenians, who attacked the city in September 432. The Corinthians now asked Sparta for help, and Pericles, the Athenian general and statesman, struck first with an economic attack on Corinth called the Megara Decree. Megara had helped Corinth in the war against Corcyra, and Pericles decided to hurt Corinth economically. The decree prevented goods from Megara from being sold in Athens. This would lead to not only the destruction of Megara, but the economic curtailment of Corinth as well.

At this stage, the allies of Sparta brought formal charges that Athens had violated the Thirty Years Peace. Led by Corinth, they charged that Athenians had been imperialistic and they needed to move to action, not words. Megara then attacked Athens for denying it access to its port. The island of Aegina, under Athenian domination but supposedly independent, agitated behind the scenes and continued to incite opposition to Athens, claiming that its independence had not been guaranteed. Some Athenian envoys, doing other business, were at Sparta and were invited to respond.

As Thucydides related, what was important in all of these discussions was not the stated causes such as Corcyra, Potidaea, or Megara, but rather the fear of Athens and its successes. The debate that Sparta now undertook was not whether to go to war, but when. The Spartan king Archidamus encouraged Sparta to delay building up its financial reserves since war is waged not by arms alone, but by money as well. The Ephors, however, were in favor of war and simply asked the question of whether the peace treaty had been broken, and whether Athens was responsible. The Spartan assembly decided that Athens had broken the treaty.

According to the Peloponnesian League’s protocol, the decision by Sparta was not binding—the league’s assembly had to vote. Sparta now called a meeting of the league’s assembly to debate the issue. The Corinthians who had urged war in the Spartan assembly now held back, so as to persuade the smaller states to support their cause. These states, not associated with trade and being near Athens, had to be convinced that the war was in their interest. Corinth argued that these smaller states depended on Corinth and other mercantile states to receive imports and to sell their goods, and the Peloponnese had the resources to win. At the league’s assembly, the majority of states voted for war.

Both sides sent envoys to each other demanding that ancient curses be resolved, but nothing would come out of it. The two sides crashed into war, with Sparta commanding all of the Peloponnese except Argos, and all of central Greece except for Plataea. Athens had its islands and Corcyra in the west. More important, the two sides differed in their resources. Athens not only had its own fleet of 300 warships, but also those of its allies, while Sparta only had the Corinthian fleet, which did not fare well at Corcyra. Sparta and its allies could put into the field 30,000 soldiers without dipping into its reserves, while Athens could put only 16,000 into the field, and the Spartans were still viewed as the best soldiers in Greece. Athens had built up a reserve of 6,000 talents (the equivalent of building 6,000 new ships) and received a yearly influx of 1,000 talents from its allies. Sparta and its allies did not have any noticeable financial reserves and nowhere near the income from its allies as Athens did. Since Sparta could not field a large navy, it would not be able to deal with the islands until Persia financed the Spartans and their fleet.

The Spartan strategy was to try to entice Athens into a great land battle in which their superior numbers and training could overwhelm the Athenians and bring them to make peace. On the other hand, the Athenians under Pericles sought to exhaust the Spartans, so he was willing to allow Attica to be attacked each year. Athens did not have the resources to garrison the mainland, as proved by their failure before the Thirty Years Peace. Pericles’s strategy was to use hit-and-run attacks on the western coast of Greece against Sparta’s allies. The plan would allow Athens to keep Sparta engaged in constant garrison duties to protect its own lands, while the Athenian fleet could engage in raids. Sparta would try to detach Athenian allies in Thrace, where it could engage with support from Boeotia. Pericles’s plan was well thought out and probably could have worked if future events had not derailed it.

The war began in March 431, when an advance group of 300 Thebans entered Plataea on the invitation of some malcontents. At first they were successful in convincing the Plataeans that they were more numerous, but when the truth was discovered, most of the Thebans were captured and executed. While the act was contrary to normal precedents, the traditional internecine conflicts between the states prompted states to carry out similar acts. The first phase of the war, the Archidamian War, began with the Spartan king advancing into Attica and ravaging the countryside. The war continued to take shape early on with the implementation of Pericles’s plan. The Athenians evacuated their countryside and swarmed into Athens. The population of the city swelled and was soon overcrowded forcing makeshift housing to occur, with many residents living in the area between the Long Walls from Athens to the Piraeus.

The Spartans advanced into Boeotia, while the Athenians sent a fleet of 100 ships to the west, where they had some successes. At this stage, the Athenians also drove out the Dorian Aeginetans from Aegina and settled it with Athenian citizens. This completed the century-old war between the two states. At the end of the first year of war in winter, the traditional oration for those who had died was given by Pericles. In the speech, Pericles praises the Athenians and their contribution to Greece.

The following year, 430, the Spartans again invaded Attica. This time, a greater danger existed for Athens—the plague. It was a new disease, and the doctors could not find a cure. With the overcrowding of the city, the disease soon wreaked horrible consequences. The number of dead continued to rise, and soon bodies began to pile up all over the city, including temples, and the dying were concentrated at the fountains to quench their thirst, possibly spreading the disease even more. The plague did not hit much beyond Athens.

The plague seemed to have originated in Africa and spread with the Carthaginian trade routes throughout the Mediterranean since both Rome and Athens were hit. Since the Peloponnese was not hit hard by the plague, it may have been associated with the grain trade. It is estimated that at least 20 percent of the population died during the outbreak that first year. The plague would return, but not as virulently as in the first year. The large Athenian fleet, along with a sizable army under Pericles, attempted to seize Epidaurus in the Argos but failed. If it had succeeded, then the Peloponnese would have been cut in two and the war may have ended. At the same time, the Athenians after a year of siege captured Potidaea and colonized the site with Athenians. The next year, 429, a greater disaster occurred when Pericles took ill with the plague and died. The rudder of the state was now gone.

From 429 to 427, the Spartans blockaded and besieged the city of Plataea. Although the Athenians said that they would help the Plataeans, no help came. During the campaign, the Spartans enveloped the city and forced the inhabitants into deprivation. In December 428, about 200 soldiers escaped. They were the lucky ones; in the summer of 427, the Plataeans surrendered, and nearly 200 along with 25 Athenians were executed. The city was razed, and Sparta now controlled the access to Thebes from the Peloponnese.

The Athenians did not help due to another issue as well—the revolt of Mytilene. The oligarchic government had always been well treated, and there was no real cause for the rebellion except the continual distrust of losing one’s autonomy to another. For two years, the Athenians besieged the city, and when it fell, the Athenian assembly ordered all the inhabitants to be executed. The next day, the assembly had a change of heart and rescinded the sentence; the ship bearing that news arrived just as the first ship had delivered news of the sentence, and so was able to forestall it. Only the ringleaders were executed and the city was razed and land was given to the Athenians. In the west, the island of Corcyra saw a terrible revolution between the democrats and oligarchs. Ultimately, the democrats won in 425 executing the oligarchs. In this war, both sides committed atrocities

During this chaos, the Athenians under Demosthenes, the leader of the War Party, campaigned in the west. This led to a struggle at Pylos and the defeat and capture of about 120 Spartans in 425, which damaged their reputation as fearsome warriors. These prisoners were kept at Athens as hostages. This effectively prevented the Spartans from attacking Attica as they had done previously. The Athenians had taken Delium in Boeotia, but then they were defeated by the Thebans and lost Delium. The Athenians had failed to follow Pericles’s advice of not attempting to control land.

The war then shifted to the north, in Thrace. In this instance, the Spartans under Brasidas had taken Amphipolis in 424 after the Athenian historian and general Thucydides had failed to fortify it. Brasidas successfully took the city, and Thucydides was banished from Athens. Although both sides now wanted peace, Brasidas of Sparta and Demosthenes of Athens continued the war. In 422, bringing his army north to Amphipolis, Demosthenes attacked and Brasidas and the Spartans counterattacked. In the battle, both leaders were killed, with Sparta winning the battle. Exhausted, both sides negotiated and the Peace of Nicias was concluded; both sides would go back to where they were in 431 and prisoners were to be exchanged. The latter occurred only due to a defensive pact between Athens and Sparta, separate from the peace treaty. The treaty could never work, though, since most of the Spartan allies, especially the Corinthians, refused to accept the situation.

In the following years, both cities vacillated between being prowar and wanting peace. In Athens, the rise of Alcibiades, the nephew of Pericles, occurred, but his erratic behavior caused many in Athens to be concerned. In Sparta, a new threat loomed—namely, the end of the peace treaty with Argos. The Spartans soon faced a potential rebellion of its Peloponnesian League with Argos at its head. To counter this situation, the Spartans under king Agis marched north. At Argos, in 418, the Argive and Athenian forces were defeated by the Spartans.

The result of this war was that the democratic government in Argos fell, and an oligarchic form arose in its place and became an ally of Sparta. At this point, the Athenians were now isolated on the Greek mainland. The new prowar party at Athens, led by Hyperbolus, blamed the Peace Party leader Nicias for its failure. Hyperbolus decided to initiate an ostracism against Nicias, but the gambit backfired when the third faction, led by Alcibiades, deserted Hyperbolus, who instead was ostracized in 417. The following year, the Athenians decided to attack Melos, an island that had refused to join the Delian League. With its capture, the Athenians now planned an even greater adventure—the conquest of Sicily.

Sicily held great allure (as well as treasures, supposedly), and its conquest, although fanciful, would have added immense prestige to Athens. The expedition was basically doomed to failure from the beginning. The Athenian people elected as the expedition’s main leaders Alcibiades, who wanted to command, and Nicias, who opposed the campaign. Alcibiades was soon involved in a scandal, the disfigurement of the Herms where statues marking crossroads had male genetalia as a sign of good luck, and fearing exile or worse, he jumped ship and defected to the Spartans. The fleet continued to Sicily and began its campaign. Nicias and the troops failed in their objective and had to begin to besiege the city of Syracuse in 414. The Spartans sent a force under its general, Gylippus, who began to fortify the city and help the Syracusans against the Athenians. At the same time, the Spartans, having received advice from Alcibiades, took the Athenian fortress at Decelea in Attica, which commanded silver mines. Nicias, in need, asked the Athenians to send help, and a second fleet was dispatched to Sicily in 413.

This fleet arrived the day after the initial one had been defeated. The Athenians failed to evacuate their forces, and after another sea battle they were defeated. The Athenians attempted to flee, and in the general pursuit, a great slaughter ensued. Nicias surrendered to Gylippus, and the Athenians surrendered to Syracuse. The Athenians were kept in miserable conditions for six months, and their allies for two months, before prisoners were sold as slaves. Most of the Athenians never saw their homeland again, and Nicias was probably executed. The disaster of Sicily led to a general rebellion of Athens’s allies in 412.

One of the results of the disaster in Sicily was a renewed war in Attica. When Alcibiades was recalled to Athens to face charges of desecrating the Herms, he jumped ship and fled to Sparta, where he was received by King Agis. He recommended to the Spartans that they invade Attica, and instead of returning each year as they had done in the previous part of the war (431-421), they should take and fortify Decelea and remain there year round. This allowed the Spartans to free 20, 000 slaves and to shut down the mines of Laurium preventing Athens from receiving funds.

This now put a strain on the Athenian treasury, which forced the Athenians to increase the tribute on their subjects. When the Athenian fleet was destroyed in Sicily, Athens was at a low point—its fleet gone, its treasury depleted, and its future army destroyed or enslaved in Sicily. At this point, the Persians supported the Spartans, Syracuse sent a fleet to help the Spartans, and Ionia revolted against the Athenians. The Peloponnese was slow to bring its forces into the Aegean, and Persia did not give its support quickly.

In Athens, the Sicilian disaster produced a revolution with the creation of the oligarchic council of 400, where upper-class wealthy Athenians took over the running of the government and replaced the Athenian Assembly with the Assembly of 5,000. The plan was for a simultaneous rebellion to take place at Samos, where the last Athenian fleet of 100 ships was stationed. The fleet, made up of poorer Athenians, uncovered the plot and prevented the coup, declaring that Athens had betrayed Athenian democracy and the fleet was the true democracy. The fleet now recalled Alcibiades, and the Athenians announced that they would continue the war against Sparta.

The 400 in Athens soon began to fight among themselves, with the moderates wanting to expand the 400 and the extremists potentially planning to surrender to Sparta. After a few months, the moderates won out, replacing the 400 with the Assembly of 5,000. This group would continue to rule Athens for several months until the Athenian fleet at Samos, commanded by Alcibiades, sailed north and achieved a naval victory over the Spartan fleet in 410 at Cyzicus. The Athenians captured numerous Spartan ships, and the Spartan commander, Admiral Mindarus, was killed. The Athenians had now retaken the Hellespont and allowed the grain ships to reach Athens and supply the city. Sparta proposed peace, but Athens rejected it. Due to lack of funds, the Athenians were not able to follow up their victory. The oligarchic revolution in Athens fell in 410.

For the next four years, Athens, led by Alcibiades, successfully reestablished its power base in the Aegean. At the same time, Persia supported the Spartans, who rebuilt their fleet after the disaster at Cyzicus. The Persian king Darius II sent his son, Cyrus the Younger, to Asia Minor as commander. Cyrus made friends with the Spartan general Lysander and supported him. Lysander promised to help Cyrus become king in exchange for Persian money. In 406, Lysander won a small naval victory at Notium near Ephesus when Alcibiades’s lieutenant, Antiochus, disobeyed his superior’s orders not to engage with the Spartans and suffered a defeat. The defeat resulted in Alcibiades not being reelected as general, and he went into exile. At the same time, Lysander was replaced as general.

The Athenian fleet, inexperienced and composed of metics and slaves who were promised freedom, successfully defeated the Spartan fleet at Arginusae, but when the Athenian fleet failed to rescue the crews of twenty-five triremes, the Athenian assembly convicted and executed six of the eight generals. These executions would deprive Athens of some of its best generals, which had an impact on the future course of the war. The anti-Lysander party at Sparta again sent a peace delegation to Athens, but it was rebuffed, allowing Lysander to retake command of the Spartan fleet.

Lysander, not of royal birth, sailed his fleet to the Dardanelles to cut off the Athenian grain supply from the Black Sea. The Athenian fleet of 180 ships now pursued Lysander in the hope of defeating the Spartan fleet and open the grain supply. Lysander successively defeated the Athenian fleet at Aegospotami in 405. Alcibiades, who lived in exile nearby, suggested that the Athenians relocate to Sestos for better security and indicated that he could get support from the Thracian kings if the Athenians gave him partial command. But the Athenians rejected his counsel and offer, and he retreated to his fortress. The Athenians sailed out and presented itself for battle but Lysander refused, and when the Athenian ships beached and began to look for food and supplies, Lysander then attacked and defeated the fleet, capturing all but twelve ships.

The Spartan victory was complete, resulting in the capture of between 3,000 to 4, 000 Athenian soldiers. Lysander ordered the slaughter of the Athenians but spared the rest of the Greek sailors and soldiers. Lysander now moved toward Athens, capturing cities and islands. Many of the Athenians and their allies fled to Athens, creating chaos and overcrowding. The Athenians intended to hold out behind their walls, but with supplies nonexistent and disease rampant, the Athenians surrendered to Lysander in March 404. In this same year, Alcibiades was killed in Asia Minor, probably assassinated on the orders of the Persian satrap Pharnabazus in response to Lysander’s request. This would further deprive Athens of a capable commander against the Spartans.

The Spartan allies Thebes and Corinth demanded that Athens be destroyed and its inhabitants enslaved, but Sparta refused since Athens had done so much for Greece. Instead, Athens was to be an ally of Sparta. Lysander probably realized that without Athens as a counterweight in the north, Thebes would rival Sparta for control. Sparta now replaced Athens, taking over its possessions and keeping the tribute for itself, with its allies receiving nothing. Sparta now set up an oligarchic regime known as the Thirty Tyrants, which ruled until 403, when it was then replaced with the restored democracy.

The Peloponnesian War ended Athens’s dominance in the Aegean. It also further destabilized the Greek world, allowing the major cities of Athens, Corinth, Sparta, and Thebes to vie for power during the next fifty years, with no one side winning permanent dominance. This continual internecine struggle allowed Macedon under Philip II and his son, Alexander the Great, to ultimately control Greece.