Following Persia's defeat Greece entered a golden age lead by Athens. Athens's greatest leader at this time was Pericles. He was a military leader who held the title of Stratagos for 32 years in a row. Under his power Athens rebuilt it's Acropolis, built the Pantheon, and expanded its public arts. It was a time of lavishness, but also a time of Athenian greed.
In purple is Sparta and its allies, this also includes the kingdom of Macedon just north of Thessaly as well as the kingdom of Thrace just west of the Athenian allied state of Byzantium modern day Istanbul. The Athenian alliance is in orange and also includes the city state of Byzantium. Sparta declared war on the Athenians in 431 BCE and put siege to Athens. But the walled city was safe from direct assault leading to a protracted siege lasting the entire war.
Athens held several advantages over the Spartan Alliance at the start of the war. First it's capital city was walled and impervious to direct assault. The Athenian alliance also controlled the seas making it harder for the Spartan alliance to work together while at the same time ensuring supplies to the besieged city of Athens. However this also meant the war would be one of attrition since Sparta was an inland state thus making the Athenian navy hold little offensive value.
Though Sparta couldn't breach the Athenian walls or threaten their navy at the start of the war it did hold a few advantages itself. Sparta's land army was the best trained in Greece and was not threatened by Athenian forces, that is because Sparta was an inland state on the Peloponnese peninsula and much all of the peninsula was either neutral or on the Spartan side. This meant that Athens didn't threaten the state of Sparta itself meaning Sparta could easily play the game of attrition. Another advantage it held over Athens was its own state's and alliance's stability. There was no infighting within Sparta's alliance but for Athens many states in its alliance or that were neutral were willing to join Sparta against Athens given the chance.
There were three turning points in the war. The first was the breakout of Typhus in Athens which was under siege by Sparta in the year 429 BCE . One third of the Athenian population died including their leader Pericles. This lead to instability in Athens over power and many betrayals and and exiles between different leading figures such as their best commander Alcibiades who became a turncoat and joined the Spartans and later helped push the Persians to aid the Spartans.
The second turning point came in the year 415 BCE. Athenian and Spartan allies on the island of Sicily were fighting and the Athenian allies requested aid. The Athenians sent a large expedition but it was a massive failure. Their forces lost 30,000-50,000 troops and the fleets sent were all destroyed. The campaign alone was a failure but this prompted many neutral and former Athenian allies to join the Spartan lead league. It also lead to more infighting in Athens when Alcibiades fled.
The third turning point in the war against Athens was when Persia decided to aid Sparta. Starting in 411 BCE they started to outfit the Spartans with fleets, money, and Persian troops. Even when the newly made Spartan fleets were destroyed Persia would supply Sparta with new ones. Finally in 407 BCE the Athenians lost control of the seas completely assuring the Spartans a victory in the war.
With the loss of supply the city of Athens starved for three years. In 404 BCE the city surrender and the Spartans entered the city bringing the war to a close. Many of the Spartan allies that had faced ruin during the war such as Thebes and Thrace called for Athens to be burned and its people enslaved, but Sparta decided to spare Athens. It destroyed the city's walls and remaining fleets leaving it defenseless should a new war should start and left. The war ended the Athenian golden age and brought an end to democracy for centuries. Athens came to be ruled by a counsel of tyrants and would continue to fight itself over democratic verse aristocratic values for decades. The war itself left Greece in ruins and open to foreign attack. Soon Macedon lead by Phillip II and Alexander the Great would conquer Greece without much resistance.
However the catastrophe that was the war did bring some advancement to Greece and humanity. The war lead Greece to rethink its ways and many of its values and philosophies. It lead to questions concerning greed, human will, politics, and ideology. Thinkers such as Herodotus and Thucydides would bring new ideas to the western civilization and would define ideas, thoughts, and values that we still hold today. The Peloponnese war is considered to be the west's first war of ideology, that of greed versus suspicion and envy.