Therewith was accomplished, what had been long in the preparing, the overthrow of the leadership which city-states had held from time immemorial in European Greece. Henceforth it was not from cities that significant movements sprang, but from ethne. Macedon itself was an ethnos, or, at least, a group of ethne, and it seemed possible to enlarge it by adding to it all the other ethne in the peninsula. The difficulty was that two other ethne, Ætolia and Achæa, the first in Central Greece and the second in the Peloponnesus, had each a similar, if less far-reaching, ambition; and while the aspirations of Ætolia to acquire territory in the Peloponnesus, and the aspirations of Achæa to expand into Central Greece, kept them normally in conflict with one another; and while each in turn (Ætolia in 245-241, Achæa in 220-217 and 212-206 B.C.) got the help of Macedon against the other, and both united only once (238-229 B.C.) in a war against Macedon, Achæa offered till 224 B.C. and Ætolia till 200 B.C. an attractive alternative for Macedonian suzerainty to ethne and city-states which could not stand alone. The natural desire of the new ethne, as of the old city-states, was, however, to be independent--a sentiment which Ætolia and Achæa shared completely; and against this powerful force Antigonus had to contend, after the Chremonidean War no less than before it. He had come so brilliantly out of the Chremonidean War, however, that ten years elapsed before his suzerainty was again challenged. His most formidable enemy, Ptolemy Philadelphus, was absorbed meanwhile with a dangerous disturbance in Ionia, occasioned by the revolt of Ptolemy, his "son", and Timarchus, his admiral, to whose aid his watchful enemy, Antiochus II, and his daring maritime rivals, the Rhodians,[124] had come (258 B.C.); but when this outbreak was brought to a close with the peace of 255 B.C.,[125] Antigonus had to anticipate a renewal of his troubles in Greece. He, accordingly, determined to cease being the anvil and to become the hammer. That meant the construction of a fleet with which to take from Egypt control of the Ægean, which had been possessed prior to 288-287 B.C. by his father and grandfather. To accomplish this end he renewed his alliance with Syria, and arranged a marriage between his son and heir, Demetrius, and Stratonice, Antiochus's sister. This being done, he sought out the admirals of Ptolemy at Leucolla near Cos, and defeated them in a great naval battle (253 B.C.). Suzerainty over the league of the Islanders was the most striking gain; but a more substantial advantage was that with his fleet he could now ward off trouble in Greece and stir it up in Ptolemy's realm. The latter he accomplished by dispatching his half-brother, Demetrius the Fair, to Cyrene and by snatching that kingdom, which had just been vacated by the death of Magas (251-250 B.C.), from the grasp of Egypt. In the former he had a rather surprising lack of success. For in 251 B.C.