 Callias formed an alliance with Philip of Macedon against Plutarch, tyrant of Eretria, with the view of extending his authority over the whole of Euboea, a design which, according to Aeschines, he disguised as a plan for uniting in one league the states of the island and establishing a general Euboean congress based at Chalcis.In response to the threat from Callias, Plutarch sought aid from Athens, which was granted in opposition to the advice of Demosthenes.An army was sent into Euboea under the command of Phocion, who defeated Callias at Tamynae in 350 BC.