(M703) One of the first things he did after defeating the Illyrians was to lay siege to Amphipolis, although he had ceded the city to Athens. For this treachery there was no other reason than ambition and the weakened power of Athens. Amphipolis had long remained free, and was not disposed to give up its liberties, and sent to Athens for aid. Philip, an arch politician, contrived by his intrigues to prevent Athens from giving assistance. The neglect of Athens was a great mistake, for Amphipolis commanded the passage over the Strymon, and shut up Macedonia from the east, and was, moreover, easily defensible by sea. Deprived of aid from Athens, the city fell into the hands of Philip, and was an acquisition of great importance. It was the most convenient maritime station in Thrace, and threw open to him all the country east of the Strymon, and especially the gold region near Mount Pangreus. This place henceforward became one of the bulwarks of Macedonia, until the Roman conquest. (M704) Having obtained this place, he commenced, without a declaration of war against Athens, a series of hostile measures, while he professed to be her friend. He deprived her of her hold upon the Thermaic Gulf, conquered Pydna and Potidæa, and conciliated Olynthus. His power was thus so far increased that he founded a new city, called Philippi, in the regions where his gold mines yielded one thousand talents yearly. He then married Olympias, daughter of a prince of the Molossi, who gave birth, in the year B.C. 356, to a son destined to conquer the world. (M705) The capture of Amphipolis by Philip was, of course, followed by war with Athens, which lasted twelve years. And this war commenced at a time Athens was in great embarrassments, owing to the social war. (M706) But he was aided by another event of still greater importance—the sacred war, which for a time convulsed the Hellenic world, and which grew out of the accusation of Thebes, before the Amphictyonic Council, that Sparta had seized her citadel in time of profound peace. The sentence of the council, that Sparta should pay a fine of five hundred talents, was a departure of Grecian custom, and Sparta refused to pay it, which refusal led to her exclusion from the council, the Delphic temple, and the Pythian games, and this exclusion again arrayed the different States of Greece against each other, as to the guardianship of the Oracle itself. Philip of Macedon seized this opportunity, when so many States were engaged in war, to prosecute his schemes. He attacked Methone, the last remaining possession of Athens on the Macedonian coast, and captured the city, and then advanced into Thessaly against the despots of Pheræ, who invoked the aid of Onomarchus, now very powerful.