Together with the kidnapped Parthian prince Augustus had given in exchange for the legion standards captured by the Parthians at Carrhae in 53 BCE, he also had given Phraates IV an enslaved Italian girl, "Thea Muse", who has become Queen Musa of Parthia.

To ensure that her child Phraataces will inherit the throne without incident, Musa persuades Phraates IV, whose greatest enemies are his own family, to give his other five sons to Augustus as hostages, thus acknowledging his dependence on Rome.

Again, Augustus uses this as propaganda depicting the submission of Parthia to Rome; he will list it as a great accomplishment in his funerary inscription, Res Gestae Divi Augusti. (The hostages include Tiridates III, whom the Romans will later try to install as a vassal king in CE 35).

He appoints Phraates V successor and in about 2 BCE is murdered by Musa.

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.