The Roman reconfiguration of the political structure in the region was essentially defensive in character, making it clear that the Senate had little interest in prosecuting an expansionist war against Parthia. However, the republican system of government was beginning to break down as Rome’s aristocrats competed for power. In 55, the triumvirate of Caesar, Pompeius, and Crassus dominated the political scene in Rome. The latter two were co-consuls that year, with Crassus designated to become governor of Syria after his term as consul was concluded. Somewhat older than the other two leaders, Crassus had not participated in a military campaign since the suppression of the slave revolt of Spartacus sixteen years earlier. Now approaching the end of his public career, Crassus apparently intended to exploit the opportunity to launch a conflict with Parthia that he expected to shower him with military glory as well as a good deal of booty.
Relations with Parthia had already been soured by Pompeius’ somewhat disrespectful treatment of Phraates with regard to formally establishing the Roman-Parthian frontier at the Euphrates. The situation became worse in 55 when Gabinius, the proconsul of Syria, sought to intervene in Parthian affairs by involving himself in the succession crisis that accompanied the enthronement of Orodes II (57–37). Gabinius had given his support to a brother of the new Parthian ruler who was contesting the succession. Relations with Parthia were to become explosive with the arrival of Crassus in Syria to replace Gabinius as proconsul in the spring of 54.
Crassus was in command of seven legions with a total of more than 40,000 troops, and he soon began making probing forays across the Euphrates into Parthian-held territory. He consolidated his foothold as he progressed with the establishment of Roman garrisons in a number of the