Achaean League (əkē´ən), confederation of cities on the Gulf of Corinth. The First Achaean League, about which little is known, was formed presumably before the 5th cent. BC and lasted through the 4th cent. BC Its purpose was mutual protection against pirates. The Achaeans remained aloof from the wars in Greece until they joined the opposition to Philip II of Macedon in 338 BC The confederation was dissolved soon after. The Second Achaean League was founded in 280 BC Sicyon was freed from the rule of its tyrant in 251 BC, and it soon joined the confederation under the leadership of Aratus. Other cities outside Achaea were incorporated on terms of equality, and in 247 BC the Macedonians were driven from Corinth. There was some promise of liberating all Greece, but unfortunately the interference of Cleomenes III of Sparta threatened the Achaean League, and in 227 BC he began a war. The Achaean League then requested (224 BC) Macedonian aid against Sparta and the Aetolian League. The result was the eclipse of the confederation until the wars between Macedon and Rome. In 198 BC the Achaeans went over to Rome and with Roman aid won practically the whole Peloponnesus, forcing Sparta and Messene to join. Later suspecting the Achaeans of again looking toward Macedon, the Romans deported (168 BC) their leaders (including Polybius) to Italy. In 146 BC the Romans waged a war against the Achaeans and easily triumphed at Corinth. The Romans dissolved the confederation, thereby ending Greek liberty.