Amminapes is mentioned only a couple of times in our sources, but he is among the more interesting characters of the history of Alexander. He was a Parthian nobleman serving the great king Artaxerxes III Ochus (ruled 358-338). This reminds one immediately of the multi-ethnic nature of the Achaemenid Empire, where non-Persians were always able to make a career. Amminapes may, for example, have known the satrap of Cilicia, a Babylonian named Mazaeus, and the Greek general Mentor of Rhodes.
However, Amminapes lost the king's favor and was forced into exile. He went to Europe and settled at the court of king Philip II of Macedonia. Here, the Parthian may have met other refugees, like the former satrap of Hellespontine Phrygia, Artabazus, and his daughter Barsine. He almost certainly met the young crown prince Alexander.
At some stage, he returned to Persia, and we find him in Egypt, where he arranged the surrender of the Persian forces when Alexander and the Macedonian army arrived in December 332. Together with the satrap Mazaces, Amminapes made sure that the take-over and occupation was an easy matter. The Parthian was to be rewarded less than two years later.
In the summer of 330, Alexander had driven his opponent, king Darius III Codomannus, to his death, and he now went on to conquer Hyrcania. After the pacification of this province of Alexander's realm, Amminapes was appointed as satrap. He was replaced not much later, but it shows that people who spoke both Persian and Greek could easily pursue a career during the crisis that was the Macedonian take-over. Artabazus and Barsine could tell similar stories.