nor their Persian predecessors—the Achaemenids—is there reliable evidence that marriage was practised between parents and their children. Reign At his accession, Phraates V inherited a long dispute between the Parthians and the Romans over Armenia and Mesopotamia. As a result, Augustus dispatched an army under his adopted son Gaius Caesar to capture both regions. Before war broke out, they were met by an emissary of Phraates V, who demanded the king's brothers be returned to him. Augustus wrote a mocking response in a letter to Phraates V, which simply addressed him as "Phraates". He demanded that Phraates relinquish his crown and give up his claims to Armenia. Not intimidated, Phraates V replied back—according to the classical Roman historian Cassius Dio—"in a generally haughty tone, styling himself King of Kings and addressing Augustus simply as Caesar". Ultimately, the two powers agreed to come to terms through diplomacy: a peace-treaty was agreed in 1 AD, which made Armenia a Roman vassal state, whilst the Romans agreed to acknowledge the Parthian Empire as its equal, and Phraates V as its rightful ruler. It was important to Phraates V that he was acknowledged by the Romans, due to his insecure domestic position in the country. However, this strategy backfired. In 4 AD, the Parthian nobility, already discontented with the son of an Italian slave-girl occupying the throne, were further angered by his acknowledgement of Roman suzerainty in Armenia, expelling Phraates V and Musa from the Parthian throne. Both fled to Rome, where Augustus welcomed them. The Parthian nobility then placed Orodes III on the throne. Coinage Phraates V's later reverse coins notably have an image of his mother, Musa, with a circular legend labelling her as "heavenly", contrary to the square legends which had been typical on Parthian coin mints. Furthermore, the title of basilissa ("queen") is also given to her, which was not necessarily only used by the wife of the king in the Hellenistic era, but also other royal women. Like his father, Phraates V's obverse coins depicts a figure resembling the Greek goddess Nike holding a ring and diadem behind his head. In the Parthian era, Iranians used Hellenistic iconography to portray their divine figures, thus the figure can be associated with the Avestan khvarenah, i.e. kingly glory. Rarely, a fire temple is depicted on the reverse of his coins. Likewise, the title of Phraates V on his coinage remained the