Along with Neoptolemus they both rose to prominence during the wars of Mithridates VI on the northern shores of the Black Sea. Archelaus was a prominent Pontic general during the First Mithridatic War (89 BC-85 BC). In 88 BC as a part of the First Mithridatic War, Archelaus and his brother were involved in a military campaign with the Pontic army against King Nicomedes IV of Bithynia. On the Amnias River the brothers had the command of the advance guard and won their first victory of the war. Neoptolemus then went on to defeat a Roman-led army at Protopachium, probably without his brother. Archelaus was next involved in Mithridates VI’s successful military campaign in conquering most of the Roman Province of Asia. Archelaus had attacked a city called Magnesia ad Sipylum or Magnesia on the Maeander. This attack failed and Archelaus was wounded in the fighting.