The two most powerful city-states in ancient Greece, Athens and Sparta, went to war with each other from 431 to 405 B.C. The Peloponnesian War marked a significant power shift in ancient Greece, favoring Sparta, and also ushered in a period of regional decline that signaled the end of what is considered the Golden Age of Ancient Greece.
The formation of the Delian League, or Athenian League, in 478 B.C. united several Greek city-states in a military alliance under Athens, ostensibly to guard against revenge attacks from the Persian Empire. In reality, the league also granted increased power and prestige to Athens.
The Peloponnesian War marked the end of the Golden Age of Greece, a change in styles of warfare and the fall of Athens, once the strongest city-state in Greece. The balance in power in Greece was shifted when Athens was absorbed into the Spartan Empire.
It continued to exist under a series of tyrants and then a democracy. Athens lost its dominance in the region to Sparta until both were conquered less than a century later and made part of the kingdom of Macedon.
REF: www.history.com
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