The origins of Armenian independence are poorly understood, but it seems that when Alexander the Great sent an army, commanded by Mithrenes, to gain control of Armenia (331 BCE),note[Arrian, Anabasis 3.16.5.] the satrap appointed by the last Achaemenid king Darius III Codomannus, a man named Orontes II, managed to remain in control of his realm. During the Second Diadoch War (318-316 BCE) an Orontes is mentioned as a supporter of Peucestas.note[Diodorus, World History 19.23.3; Polyaenus, Stratagems 4.8.3 tells the same story.] and it is likely that this is the same Orontes II.
After the battle of Ipsus (301 BCE), which marked the end of the Fourth Diadoch War, the Armenians recognized Seleucus I Nicator as their overlord.note[Appian, Syrian Wars 55.] In 281 BCE, however, the situation changed. Seleucus had expanded his power to the west but was assassinated by Ptolemy Keraunos. Seleucus' son and successor Antiochus I Soter, had difficulty to assert himself as new ruler in the Seleucid Empire. In the next year, the Carian War (also known as the First Syrian War) broke out: king Ptolemy II Philadelphus of the Ptolemaic Empire conducted a brief but successful war and conquered Ionia, Caria, Lycia, Pamphylia, and parts of Cilicia. Proceeding to Damascus, he discovered that Antiochus was quite powerful, and concluded an armistice.
In this confused situation, Ariarathes II of Cappadocia
obtained an army from Ardoates, king of Armenia, slew Amyntas, the Macedonian general, expelled the Macedonians from the land in short order, and recovered his original domain.note[Diodorus, World History 31.19.5.]
The author of thos remark, Diodorus of Sicily, calls Ardoates "king", which suggests that he believed Armenia was by now completely independent. This Ardoates is also called Orontes III. He may have been the father of king Samus.