While the discussions as to the treaty with Mancinus were pending in Rome, he attacked the free people of the Vaccaei under frivolous pretexts just as Lucullus had done sixteen years before, and began in concert with the general of the Further province to besiege Pallantia (618).

A decree of the senate enjoined him to desist from the war; nevertheless, under the pretext that the circumstances had meanwhile changed, he continued the siege.

In doing so he showed himself as bad a soldier as he was a bad citizen.

After lying so long before the large and strong city that his supplies in that rugged and hostile country failed, he was obliged to leave behind all the sick and wounded and to undertake a retreat, in which the pursuing Pallantines destroyed half of his soldiers, and, if they had not broken off the pursuit too early, would probably have utterly annihilated the Roman army, which was already in full course of dissolution.

For this conduct a fine was imposed on the high-born general at his return.