A competing coalition of Greek city-states centred around Sparta arose, and became more important as the external Persian threat subsided. This coalition is known as the Peloponnesian League. However, unlike the Hellenic League and the Delian League, this league was not a response to any external threat, Persian or otherwise: it was unabashedly an instrument of Spartan policy aimed at Sparta’s security and Spartan dominance over the Peloponnese peninsula. The term “Peloponnesian League” is a misnomer. It was not really a “league” at all. Nor was it really “Peloponnesian”. There was no equality at all between the members, as might be implied by the term “league”. Furthermore, most of its members were located outside the Peloponnese Peninsula. The terms “Spartan League” and “Peloponnesian League” are modern terms. Contemporaries instead referred to “Lacedaemonians and their Allies” to describe the “league”.
The league had its origins in Sparta’s conflict with Argos, another city on the Peloponnese Peninsula. In the 7th century BC, Argos dominated the peninsula. Even in the early 6th century, the Argives attempted to control the northeastern part of the peninsula. The rise of Sparta in the 6th century brought Sparta into conflict with Argos. However, with the conquest of the Peloponnesian city-state of Tegea in 550 BC and the defeat of the Argives in 546 BC, the Spartans’ control began to reach well beyond the borders of Laconia.