Battle of Carrhae - Political Background in Rome

Political Background in Rome

The war in Parthia resulted from political arrangements intended to be mutually beneficial for Crassus, Pompeius Magnus, and Julius Caesar — the so-called First Triumvirate. In March and April 56 BC, meetings were held at Ravenna and Luca, in Caesar's province of Cisalpine Gaul, to reaffirm the weakening alliance formed four years earlier. It was agreed that the triumvirate would marshal their supporters and resources to secure legislation for prolonging Caesar's Gallic command and to influence the upcoming elections for 55 BC, with the objective of a second joint consulship for Crassus and Pompeius. The leaders of the triumvirate aimed to expand their faction's power through traditional means: military commands, placing political allies in office, and advancing legislation to promote their interests. Pressure in various forms was brought to bear on the elections: money, influence through patronage and friendship, and the force of a thousand troopers brought from Gaul by Crassus's son Publius. The faction secured the consulship and most, though not all, of the other offices sought. Legislation passed by the tribune Trebonius (the lex Trebonia) granted extended proconsulships of five years, matching that of Caesar in Gaul, to the two outgoing consuls. The Spanish provinces would go to Pompeius; Crassus arranged to have Syria, with the transparent intention of going to war with Parthia.

The notoriously wealthy Marcus Crassus was around sixty and hearing-impaired when he embarked on the Parthian invasion. Greed is often regarded by the ancient sources, particularly his biographer Plutarch, as his major character fault and also his motive for going to war. Historian of Rome Erich Gruen believed that Crassus's purpose was to enrich the public treasury, since personal wealth was not what Crassus himself most lacked. Other modern historians tend to view envy and rivalry as his motivation, since Crassus’s long-faded military reputation had always been inferior to that of Pompeius, and after five years of war in Gaul, to that of Caesar. His major military achievement had been the defeat of Spartacus nearly 20 years earlier, and before that he had seen limited action, most notably the Battle of the Colline Gate. Plutarch notes that Caesar wrote to Crassus from Gaul, endorsing the plan to invade Parthia — an indication that he regarded Crassus's military campaign as complementary and not merely rivalrous to his own. Another factor in Crassus's decision to invade Parthia was the expected ease of the campaign. The Roman legions had easily crushed the numerically superior armies of other eastern powers such as Pontus and Armenia, and Crassus expected Parthia to be an easy target.

Cicero, however, suggests an additional factor: the ambitions of the talented Publius Crassus, who had commanded successful campaigns in Gaul under Caesar. Upon his return to Rome as a highly decorated officer, Publius took steps to establish his own political career. Roman sources view the Battle of Carrhae not only as a calamity for Rome and a disgrace for Marcus Crassus, but also as a tragedy for cutting short Publius Crassus's promising career.

Some Romans objected to the war against Parthia. Cicero calls it a war nulla causa (“with no justification”), on the grounds that Parthia had a treaty with Rome. The tribune Ateius Capito put up strenuous opposition, and infamously conducted a public ritual of execration as Crassus prepared to depart.

Despite protests and dire omens, Marcus Crassus left Rome on November 14, 55 BC. Publius Crassus joined him in Syria during the winter of 54–53 BC, bringing with him the thousand Celtic cavalry troopers from Gaul who remained loyal to their young leader until death.