The Peloponnesian War was a military conflict in Ancient Greece which lasted from 431 BCE to 404 BCE. This period of conflict radically changed the political landscape of Greece, greatly weakening the classical system of city-states which had dominated the region for over three hundred years prior to the outbreak of war. The events of the Peloponnesian War were also remarkable because this was one of the the first military conflicts to be chronicled by a contemporary, Thycidides, who wrote The History of the Peloponnesian War, a text which is still read and discussed today.
Most historians break the Peloponnesian War into three distinct phases: the Archidamian War, the Sicilian Invasion, and the Decelean or Ionian War. These conflicts were marked by wide-spread casualties in which many civilians and bystanders died or suffered greatly as a result of the destruction of crops and military maneuvers which packed people together, increasing the risk of diseases such as plague. By the end of the Peloponnesian War, a greatly weakened Athenian state had fallen, and there was widespread poverty throughout Attica, the region of Greece which Athens once ruled.
During the Archidamian War, the Greek city-state of Sparta invaded Athens and the surrounding area. The two sides exchanged wins and losses as they struggled for dominance in Attica for 10 years, eventually signing the Peace of Nicias to end the conflict in 421 BCE. Shortly thereafter, however, Athens invaded the city of Syracuse on the island of Sicily, sparking a new round of conflict. During the Athenian assault on Syracuse, the Athenians suffered a number of defeats, weakening the Athenian military and especially their navy, and setting the stage for the final stage of the war, when Sparta invaded Athens with assistance from the Persians.
During the Decelean War, the Spartans also encouraged Athenian subjects to revolt, so Athens found itself attacked from within as well as without. This ultimately proved to be too much for the belabored city-state, which ceded victory in 404 BCE. At the end of the Peloponnesian War, Sparta had succeeded in fracturing the city-state system, dominating Greece and setting the stage for further civil wars and internal struggles which ultimately brought Greece to its knees.
In addition to Thycidides, other Greeks also commented on and wrote about the Peloponnesian War, including Aristophanes, who satirized it in plays, Euripides, Sophocles, and Aristotle. The events of the Peloponnesian War attracted a great deal of attention among the Athenians and Spartans, who sensed that the war would have a dramatic impact on Greek society, as indeed it did.