First Peloponnesian War The First Peloponnesian War ( 460 BC - c . 445 BC ) was fought between Sparta as the leaders of the Peloponnesian League and Sparta ' s other allies , most notably Thebes , and the Delian League led by Athens with support from Argos . This war consisted of a series of conflicts and minor wars , such as the Second Sacred War . There were several causes for the war including the building of the Athenian long walls , Megara ' s defection and the envy felt by Sparta at the growth of the Athenian Empire . The war began in 460 BC ( Battle of Oenoe ) . At first the Athenians had the better of the fighting , winning the naval engagements using their superior fleet . They also had the better of the fighting on land , until 457 BC when the Spartans and their allies defeated the Athenian army at Tanagra . The Athenians , however , counterattacked and scored a crushing victory over the Boeotians at the Battle of Oenophyta and followed this victory up by conquering all of Boeotia except for Thebes . Athens further consolidated their position by making Aegina a member of the Delian League and by ravaging the Peloponnese . The Athenians were defeated in 454 BC by the Persians in Egypt which caused them to enter into a five years ' truce with Sparta . However , the war flared up again in 448 BC with the start of the Second Sacred War . In 446 BC , Boeotia revolted and defeated the Athenians at Coronea and regained their independence . The First Peloponnesian War ended in an arrangement between Sparta and Athens , which was ratified by the Thirty Years ' Peace ( winter of 446 – 445 BC ) . According to the provisions of this peace treaty , both sides maintained the main parts of their empires . Athens continued its domination of the sea while Sparta dominated the land . Megara returned to the Peloponnesian League and Aegina becoming a tribute paying but autonomous member of the Delian League . The war between the two leagues restarted in 431 BC and in 404 BC , Athens was occupied by Sparta . Origins and Causes . A mere twenty years before the First Peloponnesian War broke out , Athens and Sparta had fought alongside each other in the Greco - Persian Wars . In that war , Sparta had held the hegemony of what modern scholars call the Hellenic League and the overall command in the crucial victories of 480 and 479 BC . Over the next several years , however , Spartan leadership bred resentment among the Greek naval powers that took the lead in carrying the war against Persian territories in Asia and the Aegean , and after 478 BC the Spartans abandoned their leadership of this campaign . Athens , meanwhile , had been asserting itself on the international scene , and was eager to take the lead in the Aegean . The Athenians had already rebuilt their walls , against the express wishes of Sparta , and in 479 BC and 478 BC had taken a much more active role in the Aegean campaigning . In the winter of 479 – 8 BC they accepted the leadership of a new league , the Delian League , in a conference of Ionian and Aegean states at Delos . At this time , one of the first hints of animosity between Athens and Sparta emerges in an anecdote reported by Diodorus Siculus , who said that the Spartans in 475 – 474 BC considered reclaiming the hegemony of the campaign against Persia by force ; modern scholars , although uncertain of the dating and reliability of this story , have generally cited it as evidence of the existence , even at this early date , of a " war party " in Sparta . For some time , however , friendly relations prevailed between Athens and Sparta . Themistocles , the Athenian of the period most associated with an anti - Spartan policy , was ostracised at some point in the early 470s BC , and was later forced to flee to Persia . In his place in Athens rose Cimon , who advocated a policy of cooperation between the two states . Cimon was Athens ' proxenos at Sparta , and so fond was he of that city that he named one of his sons Lakedaemonios . Still , hints of conflict emerged ; Thucydides reports that in the mid 460s BC , Sparta actually decided to invade Attica during the Thasian rebellion , and was only prevented from doing so by an earthquake , which triggered a revolt among the helot s . It was that helot revolt which would eventually bring on the crisis that precipitated the war . Unable to quell the revolt themselves , the Spartans summoned all their allies to assist them , invoking the old Hellenic League ties . Athens responded to the call , sending out 4 , 000 men with Cimon at their head . However , something either in the behavior or appearance of the Athenian force insulted the Spartans and they dismissed the Athenians , alone of all their allies . This action destroyed the political credibility of Cimon ; he had already been under assault by opponents at Athens led by Ephialtes , and shortly after this embarrassment he was ostracized . The demonstration of Spartan hostility was unmistakable , and when Athens responded , events spiraled rapidly into war . Athens concluded several alliances in quick succession : one with Thessaly , a powerful state in the north ; one with Argos , Sparta ' s traditional enemy for centuries ; and one with Megara , a former ally of Sparta ' s which was faring badly in a border war with Sparta ' s more powerful ally Corinth . At about the same time , Athens settled the helots exiled after the defeat of their revolt at Naupactus on the Corinthian Gulf . By 460 BC , Athens found itself openly at war with Corinth and several other Peloponnesian states , and a larger war was clearly imminent . Early battles . As this war was beginning , Athens also took on a serious military commitment in another part of the Aegean when they sent a force to assist Inarus , a Libyan king who had led almost all of Egypt in revolt from the Persian king Artaxerxes . Athens and her allies sent a fleet of 200 ships to assist Inarus — a substantial investment of resources . Thus , Athens entered the war with her forces spread across several theaters of conflict . In either 460 or 459 BC , Athens fought several major battles with the combined forces of several Peloponnesian states . On land , the Athenians were defeated by the armies of Corinth and Epidaurus at Halieis , but at sea they were victorious at Cecryphaleia . Alarmed by this Athenian aggressiveness in the Saronic Gulf , Aegina entered into the war against Athens , combining its powerful fleet with that of the Peloponnesian allies . In the resulting sea battle , the Athenians won a commanding victory , capturing seventy Aeginetan and Peloponnesian ships . They then landed at Aegina and led by Leocrates laid siege to the city . With substantial Athenian detachments tied down in Egypt and Aegina , Corinth invaded the Megarid , attempting to force the Athenians to withdraw their forces from Aegina to meet this new threat . Instead , the Athenians scraped together a force of men too old and boys too young for ordinary military service and sent this force , under the command of Myronides , to relieve Megara . The resulting battle was indecisive , but the Athenians held the field at the end of the day and were thus able to set up a trophy of victory . About twelve days later the Corinthians attempted to return to the site to set up a trophy of their own , but the Athenians issued forth from Megara and routed them ; during the retreat after the battle a large section of the Corinthian army blundered into a ditch - ringed enclosure on a farm , where they were trapped and massacred . Athenian successes . Tanagra . For several years at the beginning of the war , Sparta remained largely inert . Spartan troops may have been involved in some of the early battles of the war , but if so they were not specifically mentioned in any sources . In 458 BC or 457 BC , Sparta at last made a move , but not directly at Athens . A war had broken out between Athens ' ally Phocis and Doris , across the Corinthian Gulf from the Peloponnese . Doris was traditionally identified as the homeland of the Dorians , and the Spartans , being Dorians , had a longstanding alliance with that state . Accordingly , a Spartan army under the command of the general Nicomedes , acting as deputy for the underage king Pleistonax , was dispatched across the Corinthian Gulf to assist . This army forced the Phocians to accept terms , but while it was in Doris an Athenian fleet moved into position to block its return across the Corinthian Gulf . At this point Nicomedes led his army south into Bœotia . Several factors may have influenced his decision to make this move . First , secret negotiations had been underway with a party at Athens which was willing to betray the city to the Spartans in order to overthrow the democracy . Furthermore , Donald Kagan has suggested that Nicomedes had been in contact with the government of Thebes and planned to unify Boeotia under Theban leadership ; which , upon his arrival , he seems to have done . With a strong Spartan army in Boeotia and the threat of treason in the air , the Athenians marched out with as many troops , both Athenian and allied , as they could muster to challenge the Peloponnesians . The two armies met at the Battle of Tanagra . Before the battle , the exiled Athenian politician Cimon , armored for battle , approached the Athenian lines to offer his services , but was ordered to depart ; before going , he ordered his friends to prove their loyalty through their bravery . This they did , but the Athenians were defeated in the battle , although both sides suffered heavy losses . The Spartans , rather than invading Attica , marched home across the isthmus , and Donald Kagan believes that at this point Cimon was recalled from exile and negotiated a four - month truce between the sides ; other scholars believe no such truce was concluded , and place Cimon ' s return from exile at a later date . Athens conquers . The Athenians rebounded well after their defeat at Tanagra , by sending an army under Myronides to attack Boeotia . The Boeotian army gave battle to the Athenians at Oenophyta . The Athenians scored a crushing victory which led to the Athenians conquering all of Boeotia except for Thebes , as well as Phocis and Locris . The Athenians pulled down Tanagra ' s fortifications and took the hundred richest citizens of Locris and made them hostages . The Athenians also took this chance to finish off the construction of their long walls . Shortly after this , Aegina surrendered and was forced to pull down its walls , surrender its fleet and became a tribute - paying member of the Delian League , completing what Donald Kagan has called an " annus mirabilis " for the Athenians . The Athenians , pleased by their success , sent an expedition under the general Tolmides to ravage the coast of the Peloponnese . The Athenians circumnavigated the Peloponnese and attacked and sacked the Spartan dockyards , whose location was most probably Gythium . The Athenians followed up this success by capturing the city of Chalcis on the Corinthian Gulf and then landing in the territory of Sicyon and defeating the Sicyonians in battle . The importance of Megara . Modern scholars have emphasized the critical significance of Athenian control of Megara in enabling the early Athenian successes in the war . Megara provided a convenient port on the Corinthian gulf , to which Athenian rowers could be transported overland , and a significant number of ships were probably kept at Megara ' s port of Pagae throughout the war . Moreover , while early modern scholars were skeptical of Athens ' ability to prevent a Spartan army from moving through the Megarid , recent scholarship has concluded that the pass of Geraneia could have been held by a relatively small force ; thus , with the isthmus of Corinth closed and Athenian fleets in both the Corinthian and Saronic gulfs , Attica was unsailable from the Peloponnese . Athenian crisis and the truce . Athens ' remarkable string of successes came to a sudden halt in 454 BC , when its Egyptian expedition was finally crushingly defeated . A massive Persian army under Megabazus had been sent overland against the rebels in Egypt some time earlier , and upon its arrival had quickly routed the rebel forces . The Greek contingent had been besieged on the island of Prosopitis in the Nile . In 454 , after a siege of 18 months , the Persians captured the island , destroying the force almost entirely . Though the force thus obliterated was probably not as large as the 200 ships that had originally been sent , it was at least 40 ships with their full complements , a significant number of men . The disaster in Egypt severely shook Athens ' control of the Aegean , and for some years afterwards the Athenians concentrated their attention on reorganizing the Delian League and stabilizing the region . The Athenians responded to a call for assistance from Orestes , the son of Echecratides , King of Thessaly , to restore him after he was exiled . Together with their Boeotian and Phocian allies , the Athenians marched to Pharsalus . They were not able to achieve their goals because of the Thessalian cavalry and were forced to return to Athens not having restored Orestes or capturing Pharsalus . In 451 BC , therefore , when Cimon returned to the city , his ostracism over , the Athenians were willing to have him negotiate a truce with Sparta . Cimon arranged a five - year truce , and over the next several years Athens concentrated its efforts in the Aegean . After the truce . The years after the truce were eventful ones in Greek politics . The Peace of Callias , if it existed , was concluded in 449 BC ; it was probably in that same year that Pericles passed the Congress decree , calling for a pan - Hellenic congress to discuss the future of Greece . Modern scholars have debated extensively over the intent of that proposal ; some regard it as a good faith effort to secure a lasting peace , while others view it as a propaganda tool . In any event , Sparta derailed the Congress by refusing to attend . In the same year the Second Sacred War erupted , when Sparta detached Delphi from Phocis and rendered it independent . In 448 BC , Pericles led the Athenian army against Delphi , in order to reinstate Phocis in its former sovereign rights on the oracle of Delphi . In 446 BC a revolt broke out in Boeotia which was to spell the end of Athens ' s " continental empire " on the Greek mainland . Tolmides led an army out to challenge the Bœotians , but after some early successes was defeated at the Battle of Coronea ; in the wake of this defeat , Pericles imposed a more moderate stance and Athens abandoned Boeotia , Phocis , and Locris . The defeat at Coronea , however , triggered a more dangerous disturbance , in which Euboea and Megara revolted . Pericles crossed over to Euboea with his troops to quash the rebellion there , but was forced to return when the Spartan army invaded Attica . Through negotiation and possibly bribery , Pericles persuaded the Spartan king Pleistonax to lead his army home ; back in Sparta , Pleistonax would later be prosecuted for failing to press his advantage , and fined so heavily that he was forced to flee into exile , unable to pay . With the Spartan threat removed , Pericles crossed back to Euboea with 50 ships and 5 , 000 soldiers , cracking down any opposition . He then inflicted a stringent punishment on the landowners of Chalcis , who lost their properties . The residents of Istiaia , who had butchered the crew of an Athenian trireme , were chastised more harshly , since they were uprooted and replaced by 2 , 000 Athenian settlers . The arrangement between Sparta and Athens was ratified by the " Thirty Years ' Peace " ( winter of 446 – 445 BC ) . According to this treaty , Megara was returned to the Peloponnesian League , Troezen and Achaea became independent , Aegina was to be a tributary to Athens but autonomous , and disputes were to be settled by arbitration . Each party agreed to respect the alliances of the other . Significance and aftermath . The middle years of the First Peloponnesian War marked the peak of Athenian power . Holding Boeotia and Megara on land and dominating the sea with its fleet , the city had stood utterly secure from attack . The events of 447 and 446 , however , destroyed this position , and although not all Athenians gave up their dreams of unipolar control of the Greek world , the peace treaty that ended the war laid out the framework for a bipolar Greece . In return for abandoning her continental territories , Athens received recognition of her alliance by Sparta . The peace concluded in 445 , however , would last for less than half of its intended 30 years ; in 431 BC , Athens and Sparta would go to war once again in the ( second ) Peloponnesian War , with decidedly more conclusive results .