Since the Senate refused to intervene on his behalf and his opponents insisted that they would accept no compromise in a matter of such national importance [that being the disbanding of Julius Caesar's forces following the Gallic Wars and the act of relieving him of command while still in Gaul and preventing him from running for the consulship while away from Rome], Caesar crossed into Cisalpine Gaul, where he held his regular assizes, and halted at Ravenna. He was resolved to invade Italy if force were used against the tribunes of the people who had vetoed the Senate's decree disbanding his army by a given date. Force was, in effect, used and the tribunes fled towards Cisalpine Gaul; which became Caesar's pretext for launching the Civil War.
And launch it, he did. In an act of pure ambition Julius Caesar started a civil war that ended up changing the face of Western civilization. The tribunes were on Caesar's side, and they had tried to reject a Senate bill that would strip him of power and remove him from the political landscape. Caesar was not pleased, and, not long after, he crossed the Rubicon river with his army, which was considered an act of war at the time. A bloody campaign began that led to the defeat Caesar's domestic enemies. He took control of Rome, and he set himself up as the first "Caesar" in a long line of Roman rulers.