A war threatens to break out between Parthia and Rome about the supremacy in Armenia and Media under the infant Phraates V.

However, when Augustus sends his adopted son Gaius Caesar into the east with proconsular powers in 1 BCE for a mission to Ariobarzanes, ruler of the Roman client kingdom of Armenia, which the Parthians have invaded, the Parthians eventually prefer to conclude a treaty in CE 1, signed on an island in the river Euphrates, by which once again Armenia is recognized as in the Roman sphere, with Ariobarzanes II of Media Atropene as client king.

Gaius is seriously wounded in CE 2 while attempting to suppress an uprising in the area of Armenia.