Question: why did athens and sparta fought the peloponnesian war

title: Peloponnesian War
text: After the death of Pericles , the Athenians turned somewhat against his conservative , defensive strategy and to the more aggressive strategy of bringing the war to Sparta and its allies . Rising to particular importance in Athenian democracy at this time was Cleon , a leader of the hawkish elements of the Athenian democracy . Led militarily by a clever new general Demosthenes ( not to be confused with the later Athenian orator Demosthenes ) , the Athenians managed some successes as they continued their naval raids on the Peloponnese . Athens stretched their military activities into Boeotia and Aetolia , quelled the Mytilenean revolt and began fortifying posts around the Peloponnese . One of these posts was near Pylos on a tiny island called Sphacteria , where the course of the first war turned in Athens 's favour . The post off Pylos struck Sparta where it was weakest : its dependence on the helots , who tended the fields while its citizens trained to become soldiers . The helots made the Spartan system possible , but now the post off Pylos began attracting helot runaways . In addition , the fear of a general revolt of helots emboldened by the nearby Athenian presence drove the Spartans to action . Demosthenes , however , outmanoeuvred the Spartans in the Battle of Pylos in 425 BC and trapped a group of Spartan soldiers on Sphacteria as he waited for them to surrender . Weeks later , though , Demosthenes proved unable to finish off the Spartans . After boasting that he could put an end to the affair in the Assembly , the inexperienced Cleon won a great victory at the Battle of Sphacteria . The Athenians captured 300 Spartan hoplites . The hostages gave the Athenians a bargaining chip .