The Peloponnesian War (431-404 BC) was a protracted and devastating conflict between the city-states of Athens and Sparta, representing the two dominant powers of ancient Greece. The war emerged from growing tensions over power, alliances, and differing political systems; Athens championed democracy and maritime trade, while Sparta upheld an oligarchic and militaristic society. The conflict began with the First Phase (Archidamian War), characterized by annual invasions of Attica by the Spartans