By 59 BC an unofficial political alliance known as the First Triumvirate was formed between Gaius Julius Caesar, Marcus Licinius Crassus, and Gnaeus Pompeius Magnus to share power and influence. It was always an uncomfortable alliance given that Crassus and Pompey intensely disliked one another. In 53 BC, Crassus launched a Roman invasion of the Parthian Empire. After initial successes, he marched his army deep into the desert; but here his army was cut off deep in enemy territory, surrounded and slaughtered at the Battle of Carrhae in "the greatest Roman defeat since Hannibal" in which Crassus himself perished. The death of Crassus removed some of the balance in the Triumvirate and, consequently, Caesar and Pompey began to move apart. While Caesar was fighting against Vercingetorix in Gaul, Pompey proceeded with a legislative agenda for Rome that revealed that he was at best ambivalent towards Caesar and perhaps now covertly allied with Caesar's political enemies. In 51 BC, some Roman senators demanded that Caesar would not be permitted to stand for Consul unless he turned over control of his armies to the state, and the same demands were made of Pompey by other factions. Relinquishing his army would leave Caesar defenceless before his enemies. Caesar chose Civil War over laying down his command and facing trial. The triumvirate was shattered and conflict was inevitable.