The Greeks lose all territory east of…
333 BCE to 190 BCE
The Greeks lose all territory east of Syria to the Parthians, a Persian dynasty in the East,
by about 250 BCE.
The Parthians bring the gulf under Persian control and extend their influence as far as Oman.
The Parthian conquests demarcate the distinction between the Greek world of the Mediterranean Sea and the Persian Empire in the East.
The Greeks, and the Romans after them, depend on the Red Sea route, whereas the Parthians depend on the Persian Gulf route.
The Parthians, because they want to keep the merchants who ply these routes under their control, establish garrisons as far south as Oman.