Hannibal, a few days after, fortified his camp six miles from Placentia, and on the following day, having drawn up his line of battle in sight of the enemy, gave them an opportunity of fighting.
48.

On the following night a slaughter was made in the Roman camp by the auxiliary Gauls, which appeared greater from the tumult than it proved in reality.

Two thousand infantry and two hundred horse, having killed the guards at the gates, desert to Hannibal; whom the Carthaginians having addressed kindly, and excited by the hope of great rewards, sent each to several states to gain over the minds of their countrymen.

Scipio, thinking that that slaughter was a signal for the revolt of all the Gauls, and that, contaminated with the guilt of that affair, they would rush to arms as if a frenzy had been sent among them, though he was still suffering severely from his wound, yet setting out for the river Trebia at the fourth watch of the following night with his army in silence, he removes his camp to higher ground and hills more embarrassing to the cavalry.

He escaped observation less than at the Ticinus: and Hannibal, having despatched first the Numidians and then all the cavalry, would have thrown the rear at least into great confusion, had not the Numidians, through anxiety for booty, turned aside into the deserted Roman camp.