Nothing is known of his early career until 342 BC, when he was appointed by Philip to govern Macedon as his regent while the former left for three years of hard and successful campaigning against Thracian and Scythian tribes, which extended Macedonian rule as far as the Hellespont. In 342 BC, when the Athenians tried to assume control of the Euboean towns and expel the pro-Macedonian rulers, he sent Macedonian troops to stop them. In the autumn of the same year, Antipater went to Delphi, as Philip's representative in the Amphictyonic League, a religious organization to which Macedon had been admitted in 346 BC.