Why did Sparta fight against Athens?

Sparta fought against Athens primarily due to political and ideological differences, culminating in the Peloponnesian War (431-404 BCE). Athens, with its powerful navy and democratic government, sought to expand its influence, while Sparta, a militaristic oligarchy, aimed to preserve its control over the Peloponnesian League and counter Athenian dominance. Tensions escalated over alliances, trade routes, and territorial disputes, ultimately leading to a full-scale conflict that reshaped the Greek world.