The War between Armenia and Iberia (AD 51) is known chiefly through its description in Tacitus' Annals. The war took place as a delicate balance of power between the Roman and Parthian Empires was in place in the Caucasus. Rome was then ruled by Claudius, Parthia by Vologases I. Two brothers then ruled the Caucasian kingdoms, Pharasmanes I in Iberia, Mithridates in Armenia. They were both dependent on Roman support, which had encouraged the Iberian conquest of Armenia (then a Parthian dependency) in 35 AD and subsequent coronation of Mithridates. However, 15 years later, trust between the brothers had deteriorated, which Tacitus blames on the intrigues of Pharasmanes' son Rhadamistus.