From 58 to 50 BC one of "Caesar's greatest legacy was conquering Gaul." Caesar had the opportunity to impress the senate and People's Assembly. Caesar wanted to claim outright control of Rome, but in order for him to do that he needed the support of the army and a reputation as a victorious general; so he chose Gaul as his vehicle to get there. Caesar left Rome for 8 to 9 years and during those years Caesar subdue the Celtic tribes in Gaul, making separate alliances with their many independent chieftains. Caesar was a busy man, but he also "adventure beyond the natural boundaries of Gaul." The region was framed by the Alps, the Rhine, the Atlantic and the Pyrenees. In 55 and in 53 he bridges the Rhine for brief campaigns into Germany. Although Caesar's campaigns into Germany and Britain they suggest that "he considers Gaul itself secure, but they proved him wrong." Caesar, however, was protecting the town of Gergovia when the Vercingetorix attacks and manages the Roman forces, killing about 700. In the end the results of this became Caesar's first defeat in all his years in Gaul. Caesar continued his services in Gaul by protecting the people from an threats. "It prompts many more tribes to come out in support of the rebels. Later on in the next siege Caesar and his troops, attempting to blockade the garrison, are themselves threatened by a large army of Gauls, but when the Romans win the first major battle between the two sides, the Gauls melt away." In order to save future lives, Vercingetorix rides out of town and surrenders. The conquest of Gaul was completed and Caesar set up an efficient provincial administration to govern the vast territories; he published his history The Gallic Wars. The Optimates in Rome tried to cut short on Caesar's term as governor of Gaul, but they made it clear that he would immediately be prosecuted if he returned to Rome as a private citizen, yet Caesar had an idea which he wanted to run for the consulship in absentia so that he could not be prosecuted. In the end both Pompey and Caesar were maneuvered into a public split; neither could yield to the other without a loss of honor, dignity, and power.