The significance of the Peloponnesian War in ancient Greece lies in its profound impact on the Greek city-states and their political landscape. Fought between Athens and Sparta from 431 to 404 BCE, it was a catastrophic conflict that ultimately led to the fall of the Athenian Empire. The war exposed the vulnerabilities and rivalries among Greek states, diminishing their power and unity. It highlighted issues related to democracy, governance, and military strategy that influenced future political theories. Additionally, the war's aftermath paved the way for the rise of Macedonia under Philip II, altering the course of Greek civilization.