The want of sincerity, which Constantine experienced in a tedious and fruitless negotiation, exasperated the fierceness of his temper; and he eagerly listened to those favorites, who suggested to him that his honor, as well as his interest, was concerned in the prosecution of the quarrel.

At the head of a tumultuary band, suited for rapine rather than for conquest, he suddenly broke onto the dominions of Constans, by the way of the Julian Alps, and the country round Aquileia felt the first effects of his resentment.

The measures of Constans, who then resided in Dacia, were directed with more prudence and ability.

On the news of his brother's invasion, he detached a select and disciplined body of his Illyrian troops, proposing to follow them in person, with the remainder of his forces.

But the conduct of his lieutenants soon terminated the unnatural contest.