Achaean League

The Achaean League (Ancient Greek: Κοινὸν τῶν Ἀχαιῶν, romanized: Koinon ton Akhaion, lit. 'League of Achaeans') was a Hellenistic-era confederation of Greek city-states on the northern and central Peloponnese. The league was named after the region of Achaea in the northwestern Peloponnese, which formed its original core. The first league was formed in the fifth century BC. Although the first Achaean League is much less well documented than its later revival, it maintained a recognizable federal structure through the early Hellenistic period, but later fell into a period of dormancy under growing Macedonian influence. The more famous second Achaean League was established in 280 BC. It allied with Antigonid Macedon at the Cleomenean War, Social War and First Macedonian War against the Aetolian League and Sparta. Its most successful leader was Philopoemen who forced Sparta to join the League. The league allied with the Roman Republic during the Second Macedonian War and the Aetolian War. The Achaean War led to the League's conquest and dissolution by the Romans in 146 BC.

The League represents the most successful attempt by the Greek city-states to develop a form of federalism, which balanced the need for collective action with the desire for local autonomy. Through the writings of the Achaean historian and statesman Polybius, this structure has had an influence on the constitution of the United States and other modern federal states.