Final answer:
The Peloponnesian League was led by Sparta and was involved in the Peloponnesian War against the Athenian Empire. Under the leadership of Pericles, Athens experienced its Golden Age, marked by prosperity, robust democratic institutions, and the dominance of the Delian League.
Step-by-step explanation:
The Peloponnesian League was led by Sparta. This league was a coalition of Greek city-states led by Sparta that was formed in opposition to the growing power of the Athenian Empire and its Delian League. In 431 BCE, tensions between these two powerful entities culminated in the outbreak of the Peloponnesian War when Sparta and its allies invaded Attica, an Athenian territory, marking the beginning of this long and destructive conflict. This war fundamentally shaped classical Greek civilization and marked a significant period of political and military history.
Under the leadership of Pericles, Athens reached its Golden Age, becoming the most powerful and prosperous polis due in part to the wealth it extracted from other members of the Delian League. It was also during this period that Athenian democracy was at its strongest, characterized by reforms such as the payment of public officials and the opening up of political offices to all citizens, not just the wealthy. Pericles' vision of an inclusive political system, where all citizens could participate in governance, underlined the democratic ideals of ancient Athens.