up Musa of Parthia as a client Queen. Indeed Musa was an Italian servant-girl who was given to the Parthian monarch Phraates IV () as a gift by the Roman Emperor Augustus. Musa quickly became queen and a favourite of Phraates IV, giving birth to Phraataces (Phraates V) about 19 BC. In 2 BC, Musa had Phraates IV poisoned and made herself along with Phraates V the co-rulers of the Parthian Empire. After a short rule, the Parthian nobility, angered by Phraates V's recent acknowledgement of Roman suzerainty in Armenia and his mother's Italian descent, deposed them both from the throne in 4 AD and installed Orodes III as king. Phraates V and Musa fled to Rome, where Augustus welcomed them. The next half century saw relations between the two nations antagonistic but not overtly hostile, with the Romans unsuccessfully supporting a series of pretender kings, including Claudius in 49 CE, indicating the extent to which Rome was attempting to influence Parthian politics for its own ends. However, during the reign of Nero, Vologases I invaded Armenia and installed his own brother on the throne, disrupting the balance of influence which had hitherto existed there. The ensuing war was ended by a compromise which allowed the Parthian prince Tiridates and his descendants to reign in Armenia on condition that he and his successors received their crown from the Roman emperor and ruled as his clients. Strabo described the Parthian Empire as the only rival existing to Rome. Relations during the Flavian dynasty During Vespasian’s rule Parthia seemed to make some attempts to strengthening the ties between the two powers, such as asking to form an alliance at the Caucasus against belligerent Sarmatian tribes and offering assistance to Vespasian against the short lived emperor Vitellius once it became clear that Vespasian would rule. However, both of these Vespasian refused. Relations in Late Antiquity In the 2nd century CE, the balance of power shifted emphatically in favour of the Romans. A series of invasions repeatedly overran Mesopotamia and sacked the Parthian capital of Ctesiphon, made substantial territorial gains in northern Mesopotamia and benefited from the manipulation of frequent Parthian dynastic civil wars, which eventually undermined the Parthian state. In 113 AD, Trajan invaded Parthia, marching first on Armenia. In 114 AD, he annexed Armenia to the Roman empire, after defeating and killing Parthamasiris, relative of Osroes I of Parthia. Successively he turned