His language and his example produced a deep effect: the army entrusted him with the supreme command.

Viriathus gave orders to the mass of his men to proceed in detached parties, by different routes, to the appointed rendezvous; he himself formed the best mounted and most trustworthy into a corps of 1000 horse, with which he covered the departure of his men.

The Romans, who wanted light cavalry, did not venture to disperse for the pursuit under the eyes of the enemy's horsemen.
After Viriathus and his band had for two whole days held in check the entire Roman army he suddenly disappeared during the night and hastened to the general rendezvous.

The Roman general followed him, but fell into an adroitly-laid ambush, in which he lost the half of his army and was himself captured and slain; with difficulty the rest of the troops escaped to the colony of Carteia on the Straits.
In all haste 5000 men of the Spanish militia were despatched from the Ebro to reinforce the defeated Romans; but Viriathus destroyed the corps while still on its march, and commanded so absolutely the whole interior of Carpetania that the Romans did not even venture to seek him there.

Viriathus, now recognized as lord and king of all the Lusitanians, knew how to combine the full dignity of his princely position with the homely habits of a shepherd.