Polybius says, have begun at some time after 315 B.C. when Cassander came to the throne of Macedonia, and have been completed in thirty years from that date. The earlier part of the mischief was done by Cassander and Demetrius Poliorcetes, the rest by Antigonus Gonatas son of Demetrius[252]. [250] Smith's _Dictionary of Geography_, article Achaia: and Smith's _Atlas of Ancient Geography_. [251] For the early history of Achaia see Polybius II. 37-41: Shuckburgh, translation, pages 134-137. The story about Croton and Sybaris may be incorrect (Grote, Part II. end of chapter XXXVII.): but it shows that Polybius believed the good government of the Achæans had been established long before the battle of Leuctra. [252] Polybius II. 41. About the year 283 B.C. it chanced that the attention of Antigonus was called away from the affairs of Greece; and the Achæans, being thus delivered from his interference, before long began to restore their federal union. At first, about 280 B.C., the renewed league consisted of only four of the cities: then it was joined by three more, and probably before long it included all the rest:--the whole number being now reduced to ten, for four had ceased to exist, and only two new ones had grown up[253]. For about thirty years the league did not include any cities outside Achaia: but in 251 B.C. Aratus of Sicyon, when only twenty years of age, rescued his native city out of the power of its tyrant by surprising the garrison, and, in order to provide for its future safety, induced his fellow-citizens to enrol their state as a member of the confederation. In the year 245 B.C. he was elected to the office of strategus or chief magistrate of the league: and that office he held, as a general rule, thenceforward in alternate years till his death thirty-two years later. He was most active and skilful in bringing cities into the league. In his second term of office he surprised and overpowered the Macedonian garrison which held Acrocorinthus, and thus set Corinth free. The liberated Corinthians were glad to join the Achæans, and the league, gaining possession of the Corinthian citadel which commanded the Isthmus, was able thenceforth to protect not only its own cities but the whole of the Peloponnesus against any enemy that came by land[254]. After this many other cities gave in their adhesion: the most important of those that joined before 227 B.C. were Megara, Trœzen, Epidaurus, Cleonæ, Mantineia, Phlius, Megalopolis, and Argos[255]. [253] Polybius II. 41. For the names of the cities see also Mr Shuckburgh's Introduction, pp. xlviii, xlix. [254] Polybius II. 43. [255] For a list of the cities in the league see Freeman, _Federal Government_, pp. 713-714.