 However, 15 years later, trust between the brothers had deteriorated, which Tacitus blames on the intrigues of Pharasmanes' son Rhadamistus.Fearing usurpation by Rhadamistus, his father convinced him to make war upon his uncle and claim the Armenian throne for himself.The Iberians invaded with a large army and surrounded Mithridates at the fortress of Gorneas (Garni), which was garrisoned by the Romans under the command of Caelius Pollio, a prefect, and Casperius, a centurion.