When Sparta, in the second half of the sixth century, had managed to conquer a large part of the Peloponnese and had reorganized its Constitution, it continued to have one of its most dangerous enemies in the neighboring polis of Argos. To safeguard the survival of his regime, as well as control over the helots, Sparta being the strongest military state in Greece, he felt the need to have the support of other cities. This is how the Peloponnesian League was born .
The Peloponnesian Confederation or League encompassed Corinth and all the City-States (or poleis ) of the Peloponnese, with the exception of Argos and a few other small towns. Sparta, the most powerful state of the Peloponnesian League, promised not to conquer new lands and the other cities to respect its regime:they all formed a sinmachy , a military alliance by which they were obliged to contribute with military contingents whenever necessary and which had to be commanded by Spartan chiefs, since Sparta remained the hegemonic city within the sinmachy .
Peloponnesian League Organization
The cities united in this sinmachia they retained their autonomy and their internal policy and did not have to pay taxes, since there was no permanent government body or special magistrates . They all had freedom of trade and foreign relations, but they had to respect not to wage war among themselves and contribute military contingents when all of them, led by Sparta, had to wage war against other cities outside their Alliance.
This Confederation, which did not pretend to have a political character, in its beginnings, fought above all against the establishment of tyrannies. Throughout the 5th century, all the cities that made it up had more or less defined aristocratic regimes.
This Confederation did not become a confederate State, however, the political and military importance that it had, is only comparable to that of the Athenian Confederation. During the Persian Wars it was a military organ decisive in defeating the Persians and a few decades later, managed to defeat the allied democratic cities of Athens.
In the first half of the fourth century, the hegemony of Sparta over the other cities of the League was transformed into a clear Spartan imperialism and it was then that the Second Athenian Confederation and the army of Thebes managed to defeat it for the first time in the military field, in the battle of Leuctra. In Hellenistic times the Peloponnesian League continued to exist.
The Spartan State underwent a reorganization in the years following the Second War against Messenia and the institutions were not, therefore, the work of a single legislator, Lycurgus. Once configured, these institutions would not undergo substantial changes until the first half of the fourth century BC, when a serious crisis arose that threatened the entire social and state organization, but, in the Hellenistic era, many of the basic institutions created continued to be preserved. in the 6th century BC