After a tumultuous political situation in Rome during 58 BC, again strengthened senatorial party. In 57 BC, Titus Annius Milo was elected as the Tribune. Titus Annius Millo was an opponent of Publius Clodius. That same year, Optimates managed to bring back Cicero from exile. A festive welcome in Rome was prepared to Cicero. Triumvirs were not satisfied with the development of that events in Rome. Pompey quarrelled with Crassus and he again came on to the Senate side. Pompey was given extraordinary powers concerning a supply of Rome. Rome at that time was full of street clashes between supporters of Publius Cloudius and Titius Annius Milo. In the Senate began more frequent speeches against triumvirate. Gaius Julius Caesar took all measures in order to restore and strengthen the triumvirate.
In the spring of 56 BC, was held a triumvirate meeting in Lucca. A meeting in Lucca was characterized by an extraordinary ceremony. The political alliance between Caesar, Pompey and Crassus was secured and the rights of triumvirate were expanded. Caesar command in Gaul was extended by five years. Pompey and Crassus were elected as consuls for the 55 BC, after which Pompey should have governed the Spain for 5 years and the same goes for Crassus in Syria. Crassus was attracted by Syria because it was a wealthy country and it was thirsty for war glory in the battles against the Parthian empire.
Pompey and Crassus in spite of certain resistance of Optimates managed to achieve the plan which they plot in Lucca. Crassus went to Syria even before the end of the consulship in Rome, while Pompey stayed in Italy, governing Spain through legacies.
During 54 BC, Crassus intruded in Mesopotamia and he conquered a series of cities. In the winter he returned to Syria. In 53 BC, he started a new campaign. The Romans were not used to natural conditions in Mesopotamia. Their guides were unreliable. Finally, in the battle of Carrhae, Crassus clashed with a Parthian army. Parthian army was composed of excellent cavalry. Parthians showered Crassus army with a rain of arrows. Crassus son Publius Licinius died in that battle. A large number of Romans was killed and captured. Crassus accepted Parthian proposal to enter into negotiations with them. During negotiations Crassus was killed.
Parthians crossed the Euphrates despite great resistance to the Romans. Parthians remain on the territory of Syria. During 50’s, riots in the Syria forced Parthians to return to east of the Euphrates river. From the period of Crassus campaign, a Parthian question played a major role in the foreign policy of Roman Republic in the east.