 Although distant provinces like Bactriana had often been restless under Achaemenid rule, Bactrian troops nevertheless fought in the decisive Battle of Gaugamela in 330 BC against the advancing armies of Alexander the Great.The Achaemenids were decisively defeated by Alexander and retreated from his advancing army of Greco-Macedonians and their allies.Darius III, the last Achaemenid ruler, tried to flee to Bactria but was assassinated by a subordinate lord, the Bactrian-born Bessus, who proclaimed himself the new ruler of Persia as Artaxerxes (V).