Darius III
The presence of the three ethnicities of Indian soldiers on all the tombs of the Achaemenid rulers after Darius, except for the last ruler Darius III who was vanquished by Alexander at Gaugamela, suggest that the Indians were under Achaemenid dominion at least until 338 BCE, date of the end of the reign of Artaxerxes III, before the accession of Darius III, that is, less than 10 years before the campaigns of Alexander in the East and his victory at Gaugamela.