The Classical Period Achaemenid and Hellenistic trade in the Indian Ocean

Any attempt to consider trade in the Indian Ocean during the Achaemenid and Hellenistic periods will stumble on a major objection: most ofDarius' contemporaries or Antiochus Ill's entourage were ignorant of what the Indian Ocean was! Pliny is the first Classical author to use this term in the first century AD; a few years or decades later-orbefore?- the anonymous author of the Periplus describes an Erythra thalassa from Zanzibar to Cape Comonn which corresponds approximately to our Indian Ocean (Rouge 1988). However, in the time of Achaemenid and Seleucid kings, the tenn Erythra thalassa was restricted to our modem Red Sea and/or Arab-Persian Gulf, and almost nothing was known by westerners of what existed beyond Bab al-Mandab and Ras Musandam.