There were three Peloponnesian wars. The city-states who fought against each other were Athens and Sparta. The first one began when Sparta did not let Athens rebuild the city wall and when Sparta did not accept reinforcements from Athens when they were trying to help. The first war began in 459 B.C. and was 15 years long. Because the city-states lost so many soldiers and possessions the city-state kings made a peace treaty which was called, “The Thirty Year’s peace.” Athens was the one guilty of breaking the peace treaty which lead into the next war.
The second Peloponnesian war was called The Archidamion war and began in 432 B.C. it was hard for either Athens or Sparta to win a battle because Athens preferred naval battles while Sparta preferred land battles. In 430 B.C. a plague struck Athens and killed 30,000 people. After this happened there was no formal peace treaty that ended the wars. Instead, Athens was forced to go home and protect their city while Sparta asked the city-states’ government that were around Sparta to help them in destroying Athens.
For whatever reason, the Spartans did not destroy Athens quickly. This caused the Athenians to make a small comeback in the war. In 406 B.C. Athens won a naval victory, but could not destroy the Spartans so Athens chased them to the Hellespont, because that is where Athens got its grain, and without grain, Athens could not eat. Athens lost the war because the wall of their city was torn down, their naval fleet was destroyed, and all Athenian colonies were freed from obligations to the city. Athens was weakened by the Peloponnesian wars so it was easier for Alexander the Great to conquer them.