The Campaign of Alexander III
According to the ancient historian Arrian's work "Alexander's Anabasis", in the city of Opis in 324 BC Alexander the Great addressed his soldiery and said:
"Setting out from this country, which could not adequately feed even yourselves, I immediately opened the Straits of the Hellespont for your sakes, although at the time the Persians ruled the sea. Thereafter, having vanquished the satraps of Darius with my cavalry, I placed the whole of Ionia under you, as well as the whole of Aeolis, both Phrygias and the Lydians, and I besieged and took Miletos. I allowed you the benefit of the revenues from all the other countries, which willingly bowed to my might. To you belong also all the riches of Egypt and Kyrene, which I took without a fight. In your possession are Koile Syria, Palestine and Mesopotamia. Yours too are Babylon, Baktria and Susa. Yours is the wealth of the Lydians, the treasures of the Persians and the riches of India and of the ocean."
Arrian thus presents the magnitude of the overland campaign carried out by Alexander's Macedonian troops. Alexander also assigned to his admiral Nearchos the extremely important mission of exploring the coasts of the Indian Ocean and the Persian Gulf.