Of course Lepidus armed in Etruria not for the senate, but for the insurrection-- sarcastically declaring that the oath which he had taken bound him only for the current year.

The senate put the oracular machinery in motion to induce him to return, and committed to him the conduct of the impending consular elections; but Lepidus evaded compliance, and, while messengers passed to and fro and the official year drew to an end amidst proposals of accommodation, his force swelled to an army.
When at length, in the beginning of the following year (677), the definite order of the senate was issued to Lepidus to return without delay, the proconsul haughtily refused obedience, and demanded in his turn the renewal of the former tribunician power, the reinstatement of those who had been forcibly ejected from their civic rights and their property, and, besides this, his own re-election as consul for the current year or, in other words, the -tyrannis- in legal form.
Outbreak of the War Lepidus Defeated Death of Lepidus Thus war was declared.

The senatorial party could reckon, in addition to the Sullan veterans whose civil existence was threatened by Lepidus, upon the army assembled by the proconsul Catulus; and so, in compliance with the urgent warnings of the more sagacious, particularly of Philippus, Catulus was entrusted by the senate with the defence of the capital and the repelling of the main force of the democratic party stationed in Etruria.

At the same time Gnaeus Pompeius was despatched with another corps to wrest from his former protege the valley of the Po, which was held by Lepidus' lieutenant, Marcus Brutus.

While Pompeius speedily accomplished his commission and shut up the enemy's general closely in Mutina, Lepidus appeared before the capital in order to conquer it for the revolution as Marius had formerly done by storm.
The right bank of the Tiber fell wholly into his power, and he was able even to cross the river.