4. The Chalcidian, son of Mnesarchus, together with his brother Taurosthenes, succeeded his father in the tyranny of Chalcis, and formed an alliance with Philip of Macedon in order to support himself against Plutarchus, tyrant of Eretria, or rather with the view of extending his authority over the whole of Euboea--a design which, according to Aeschines, he covered under the disguise of a plan for uniting in one league the states of the island, and establishing a general Euboean congress at Chalcis. Plutarchus accordingly applied to Athens for aid, which was granted in opposition to the advice of Demosthenes, and an army was sent into Euboea under the command of Phocion, who defeated Callias at Tamynae, B. C. 350. (Aesch. c. Ctes. §§ 85-88, de Fals. Leg. § 180; Dem. de Pac. § 5; Plut. Phoc. 12.) After this, Callias betook himself to the Macedonian court, where he was for some time high in the favour of the king; but, having in some way offended him, he withdrew to Thebes, in the hope of gaining her support in the furtherance of his views. Breaking, however, with the Thebans also, and fearing an attack both from them and from Philip, he applied to Athens, and through the influence of Demosthenes not only obtained alliance, and an acknowledgment of the independence of Chalcis, but even induced the Athenians to transfer to that state the annual contributions (συντάξεις) from Oreus and Eretria, Callias holding out great promises (apparently never realized) of assistance in men and money from Achaia, Megara, and Euboea. This seems to have been in B. C. 343, at the time of Philip's projected attempt on Ambracia. Aeschines of course ascribes his rival's support of Callias to corruption; but Demosthenes may have thought that Euboea, united under a strong government, might serve as an effectual barrier to Philip's ambition. (Aesch. c. Ctes. § 89, &c.; Dem. Philipp. 3.85; Thirlwall's Greece, vol. vi. p. 19.) In B. C. 341, the defeat by Phocion of the Macedonian party in Eretria and Oreus under Cleitarchus and Philistides gave the supremacy in the island to Callias. (Dem. de Cor. §§ 86, 99, &c.; Philipp. 3. §§ 23, 75, 79; Diod. 16.74; Plut. Dem. 17.) Callias seems to have been still living in B. C. 330, the date of the orations on "the Crown." See Aesch. c. Ctes. §§ 85, 87, who mentions a proposal of Demosthenes to confer on him and his brother Taurosthenes the honour of Athenian citizenship.