ACHAIA, ak-ā′ya, or ACHÆA, ak-ē′a, according to Homer, southeastern Thessaly, where was Phthia, the home of Achilles. In later history, a strip of Peloponnesus along the southern shore of the Corinthian Gulf, rising from the coast to wooded hills abounding in beasts of the chase; the uplands were fertile with grapes, olives and other fruits. The nome called Achaia (including Elis) in modern Greece (pop. 255,000), the northwestern part of Morea with capital at Patras, occupies the same location except along the west coast, on the Ionian Sea. When it first appears in authentic history (Herodotus), it is a confederacy of 12 towns – Pellene, Ægeira, Ægæ, Bura, Helice, Ægium, Rhypes, Patræ, Pharæ, Olenus, Dyme and Tritæa – headed by Helice, and keeping much to itself in Greek affairs. Helice was destroyed by an earthquake and swallowed by the waves 373 b.c., and Ægium succeeded to the hegemony; and at some time unknown Olenus was destroyed.
The League took no share in the Peloponnesian war, but the Macedonian supremacy and the dynastic struggles after Alexander's death broke it up altogether. Some of the remaining 10 towns were held by Macedonian garrisons, some by local tyrants, a state of disunion equally gratifying to Macedonia and intolerable to Greek patriots. In 280, when several kings were dead, Macedonia in confusion, and the great Pyrrhus absent in Italy, Patræ and Dyme, the two westernmost towns, formed an alliance; Tritæa and Pharæ joined them; and the new Achaian League, famous in history, which gave southern central Greece more than a century of order and good government, was begun. The cities probably drove out their garrisons or rulers, as later ones certainly did. Five years afterward Ægium expelled its garrison and joined the League; Bura was freed and its tyrant slain by its people and their exiled brethren, and joined them; and Iseas, tyrant of Ceryneia, seeing how events were trending, voluntarily surrendered his position with a guaranty of safety, and annexed the city to the League. Seven towns were now included; and the other three were recovered and annexed not long after. But all were small and poor; fortunately for the League, as it was thought too insignificant to molest, and grew up peacefully and solidly for some 30 years. The chief name in its early history is Markos of Ceryneia, who helped liberate Bura even before his own city was freed, and seems to have been the Washington of the League. But its first entrance into the role of a great Greek political state began with the expulsion in 249 of the tyrant of Sicyon by Aratus of that city, who induced it to join the League; it not only gained thereby the first city outside the old Achaian confederacy, and became more or less Pan-Greek, but gained Aratus, its second founder, and a statesman and administrator of high order, though his jealousy of other leaders and his military incompetency injured it deeply. A still greater accession came in 242, when Corinth expelled its Macedonian garrison and joined; and in 234 Lydiadas, tyrant of Megalopolis, the powerful city founded by Epaminodas, voluntarily resigned his place like Iseas and brought in his city, being made commander-in-chief of the League's army the next year. Before the century had begun its last quarter the League included all northern and central Peloponnesus, and many towns elsewhere.
The League was a federal union of absolutely independent states, each having equal power in the Council, which met twice a year – at first and for a long time in a grove near Ægium, but later, at Philopœmen's motion, in the League cities in rotation. The vote of each city was given as a unit, not by elected delegates, but by any of its citizens who were present, any one over 30 having a right to be so; attendance therefore naturally fell to the richer citizens with means and leisure, and the assembly was a rough representative body of the leading men. The union acted as a unit in foreign affairs, and there was a secretary to record the debates and resolutions. The head officer was the strategos, who was commander-in-chief and civil president at once; he had under him a hipparchos (cavalry commander) and nauarchos (admiral), and a board of 10 demiourgoi as assistants in the Council.
The League of course had its internal feuds and discordances of policy; and the Ætolian League north of the Gulf (only half Greek, and wholly barbarian in instability and lack of pro-Greek feeling), which alternately allied itself with it and ravaged its territory, was a mischievous rival and enemy. But the League would probably have fully held its own till the Romans came, but for Sparta. Cleomenes II had revolutionized that state, which had shrunk into the narrowest of oligarchies and could not maintain its position; he had turned it into a socialistic one, and wished to force the League to join him in a great Peloponnesian union, of which Sparta would be master, imposing both its foreign policy and perhaps its internal organization on the rest, and which would destroy the internal independence of the League and menace the possessions of every property-holder in it. The League was badly defeated by Cleomenes in the field, and was between hammer and anvil; for the only power which could save it was Macedonia, its natural foe and old master, and Antigonus Doson refused to give aid unless the citadel of Corinth, the key of Peloponnesus, held by the League, were given up to him. Aratus felt, however, that the suzerainty of Macedonia, how that the League was strong enough to prevent active tyranny, was a less evil than the mastery of Cleomenes; and by cunning management he induced the League to pay the price asked for Antigonus' help. Cleomenes was crushed at Sellasia, and his Spartan constitution came to an end, and the League became a dependency of Macedonia. Yet Aratus' policy was justified by events so far as the League was concerned; it did not suffer from Macedonian tyranny, though the chance of forming a united Greece was at an end. But that was probably as little possible under Cleomenes as under Macedonia.
In point of fact the destroying enemy was not Macedonia but Rome. Under the noble and able Philopœmen of Megalopolis, soldier and statesman of high rank, the League was prospering and giving the citizens an enviable government. But a pro-Roman policy prevailed, and Philopœmen left the country. In 198 it allied itself with Rome against Macedonia, and this was always the beginning of the end with the other party to a Roman alliance. There were wars against Sparta, and a struggle between Roman and anti-Roman partisans in the assembly, with Roman envoys and intriguers to fan the flames. Finally, in 167, the Romans deported the flower of the Achaian citizens to Italy, many of them being imprisoned, others – as the future historian Polybius (q. v.), then a youth of 18 – kept as hostages but given Roman advantages. The last struggle took place in 146, when Mummius defeated the League at Corinth, and the independence of Greece or any fraction of it was at an end. All southern and central Greece was made a Roman province called Achaia.
The First-hand authority for the League is Polybius, unfortunately extant only in fragments; in some parts he is pieced out by Livy, passages of whose work are often obvious translations from Polybius. In English the one great work is E. A. Freeman's ‘History of Federal Government,’ nearly all devoted to the Achaian League (London 1893).