The sharer of his aspirations and the cause in considerable measure of his defeat was his son Demetrius, surnamed Poliorcetes, or "Taker-of-Cities." By his disobedience to orders at Gaza and his impetuosity in action at Ipsus, he had done most to lose his kingdom; but after the death of his father he still retained the dominion of the sea, and, with it, value as an ally and ability to use his forces at such points as he himself chose. After some years of aimless adventuring and galling inactivity he chose to use them in the attempt, twice vainly made already in coöperation with his father, to seize Greece and Macedon. His strength was incomparably inferior to that used on the earlier occasions and he had still watchful enemies on all sides. The essential difference was that the house of Antipater, which had ruled Macedon and Greece since Alexander the Great had crossed into Asia, was now represented, not by Antipater's able son, Cassander, who died in 297 B.C. after a reign of nineteen years, but by his weakly and dissentious children. These looked on inactive while he blockaded Athens (295-294 B.C.) and starved it into submission; whereupon he brushed them aside and took their place as king of Macedon and suzerain of Greece. Since his wife was Phila, Cassander's sister, his son, Antigonus, surnamed Gonatas, was a grandson of Antipater I, no less than Antipater II, who was now the sole survivor of Cassander's family. Hence, if the right of Demetrius Poliorcetes to the Macedonian throne rested upon nothing more substantial than the frustrated ambition of his father, the right of his son was flawless after the death of Antipater II. This, however, occurred in 288-287 B.C. at the very time when Demetrius, on being expelled from Macedon, abandoned Greece and went to meet captivity in Asia for the rest of his life. Left behind in Greece, Antigonus Gonatas exercised a watchful suzerainty there without being king of Macedon, which Pyrrhus of Epirus and Lysimachus of Thrace shared for a few years (288 to 284-283 B.C.), Lysimachus, Seleucus, and Ptolemy Ceraunus held alone in rapid succession for another interval (283-280 B.C.), and Celts from the north plundered and harried for three years. It was not till 277 B.C. that Antigonus succeeded in freeing it from its troubles and making it the base of his operations in Greece. He therewith planted in Europe the dynasty which ruled Macedon till the Roman conquest (168 B.C.).