The Peloponnesian War began when Sparta made demands which Athens had no intentions of executing, fearing initial concessions would lead to further demands. In response, Athens made its own demands, which Sparta rejected. The nature of demands isn’t important, what is important is the two sides chose to go to war.
Pericles, one of the most respected members of Athenian society, convinced the rest of his city-state to abandon the outlying territories. His plan required all of Athens’s citizens take refuge behind the city’s walls and not engage the Spartans on land. There was no denying the Spartan’s strength on land but the Athenians were masters of the sea. His plan was to take refuge in the city, resupply and feed the citizens through the ports, and continue foreign trade to support the people. The though was that if they could hold out long enough the Spartans would be unable to continue their attack and Athens would emerge without having lost unnecessary lives.
The plan proposed by Pericles was followed until a plague broke out in the packed city within a few years. With so many people in such close quarters the plague spread like wildfire and eventually killed over thirty thousand Athenians, including Pericles.
When Pericles died so did the more conservative approach to the war with Sparta. Athens began to go on the offensive and by the end of the war (almost thirty years later) Athens went from being the most powerful of the Greek city-states to being under Spartan rule.
