 These achievements and the support of his veteran army threatened to eclipse the standing of Pompey, who had realigned himself with the Senate after the death of Crassus in 53 BC.With the Gallic Wars concluded, the Senate ordered Caesar to step down from his military command and return to Rome.Leaving his command in Gaul would mean losing his immunity to criminal prosecution by his enemies; knowing this Caesar openly defied the Senate's authority by crossing the Rubicon and marching towards Rome at the head of an army.