In 275 BC, after campaigning in Italy and Sicily for seven years, king Pyrrhus of Epirus returned to Epirus. His treasury depleted by his western campaigns, he planned a new campaign, this time east into Macedonia. The expedition originally planned as a limited raid turned into a full-scale invasion when Pyrrhus met with more success than he expected. After defeating Antigonus Gonatas, the king of Macedonia, at the Battle of the Aous he conquered most of his kingdom. Antigonus held on to several coastal cities due to Pyrrhus' inability to take coastal cities because he lacked a strong fleet. Antigonus himself had a strong fleet and was able to reinforce and supply his coastal holding at will.