->''"Creator/{{Thucydides}}, an Athenian, wrote this history of the war between the Peloponnesians and the Athenians, from the moment the conflict broke out, for he believed that it would be a great war and more worthy of remembrance than any that had preceded it. This belief was not without its grounds."''

The Peloponnesian War, one of the largest conflicts in the Greek City State era, pitted the Athenian-led Delian League (sometimes also known as the Athenian Empire) against the Spartan-led Peloponnesian League. The war can be separated into three phases:

'''Phase One''', the "Archidamian War," established the Athenian Navy as a preeminent dominant force in the sea, able to suppress dissent in its empire as well as foil Spartan invasions in the Athenian home state of Attica. This phase lasted from 431-421 BC.

'''Phase Two''' saw an attempted Athenian invasion of Sicily in 415 BC, in what can only be described as an act of wanton imperialism. The war pitted Athens against the city-state of Syracuse, which was nominally supported by Sparta. In a shocking turn, the entire invading Athenian army was massacred in 413 BC, changing the tide of the war. This section of the Peloponnesian war is widely remembered to this day as an example of the disastrous results that can happen if a war is undertaken poorly or without proper justification.

'''Phase Three''', the "Ionian War," was the final phase of the conflict. The Spartans besieged Athens by land, and the Athenian Navy was unable to break the siege, though it could supply itself with grain due to the lack of a significant Spartan naval presence. With support from the Persians, Sparta began to develop a powerful navy, and it began to fight the Athenian navy across the Aegean Sea. With the Battle of Aegospotami (near modern-day Turkey) the Spartan Navy won a decisive victory over that of Athens. This defeat marked the end of the Athenian Empire, which surrendered in 404 BC.

!!Tropes as portrayed in fiction:
* AthensAndSparta: The TropeMaker and TropeCodifier as the two city-states which were formerly allied during the UsefulNotes/GrecoPersianWars launched into a hegemonic struggle for all of "Hellas", with the two civilizations being paired eternally as contrasts, with Athens being, as Pericles noted, "the School of Hellas" while the Spartans were a warlike bunch of semi-barbarians. Of course the histories we have come entirely from Athenians. It is often forgotten that history is not so generous to the Athenians, what with Alcibiades RunningBothSides, Creator/{{Xenophon}} being an Athenian who fought ''for'' Sparta and more or less wrote about how rad they were, and the most famous section in Thucydides dealing with Athenian brutality.
* ObligatoryWarCrimeScene: ''The Melian Dialogue'' deals with Athenians sacking and destroying Melos, to MakeAnExampleOfThem by invoking DontMakeMeDestroyYou and warning them that ResistanceIsFutile.
* WarIsHell:
** It was at this time that the first antiwar plays were made; ''Theatre/{{Lysistrata}}'' is the one that has stood the test of time.
** Some parts of Thucydides' "Peloponnesian War" also stick in the mind, e. g. the war of Athens against Melos (featuring the famous "Melian dialogue") which ended with the Athenians killing all adult male Melians and selling the women and children into slavery.

!!Depictions in fiction:

* ''Theatre/{{Lysistrata}}''
* ''Theatre/TheAcharnians''
* Thucydides' ''History of the Peloponnesian War'' is one of the first modern analyses of a war. He died sometime before the end of the war, so it doesn't cover the last few years, but nevertheless, it's usually accepted as a nice (generally) unbiased version.
* ''VideoGame/EmpireEarth'' has the war during its Greek campaign. The mission consists first of getting your citizens inside the walls, surviving a plague, getting food from allied cities, defending allied cities, and defeating the Spartans.
* ''VideoGame/AssassinsCreedOdyssey'' takes place in and around 431 BC, at the beginning of the Archidamian War.