Meanwhile Hannibal got possession of Clastidium, by the treachery of a certain Brundisian, to whom it had been entrusted by the Romans. Having become master of the garrison and the stores of corn he used the latter for his present needs; but took the men whom he had captured with him, without doing them any harm, being desirous of showing by an example the policy he meant to pursue; that those whose present position towards Rome was merely the result of circumstances should not be terrified, and give up hope of being spared by him. The man who betrayed Clastidium to him he treated with extraordinary honour, by way of tempting all men in similar situations of authority to share the prospects of the Carthaginians. But afterwards, finding that certain Celts who lived in the fork of the Padus and the Trebia, while pretending to have made terms with him, were sending messages to the Romans at the same time, believing that they would thus secure themselves from being harmed by either side, he sent two thousand infantry with some Celtic and Numidian cavalry with orders to devastate their territory. This order being executed, and a great booty obtained, the Celts appeared at the Roman camp beseeching their aid. Tiberius had been all along looking out for an opportunity of striking a blow: and once seized on this pretext for sending out a party, consisting of the greater part of his cavalry; and a thousand sharp-shooters of his infantry along with them; who having speedily come up with the enemy on the other side of the Trebia, and engaged them in a sharp struggle for the possession of the booty, forced the Celts and Numidians to beat a retreat to their own camp. Those who were on duty in front of the Carthaginian camp quickly perceived what was going on, and brought some reserves to support the retreating cavalry; then the Romans in their turn were routed, and had to retreat to their camp. At this Tiberius sent out all his cavalry and sharp-shooters; whereupon the Celts again gave way, and sought the protection of their own camp. The Carthaginian general being unprepared for a general engagement, and thinking it a sound rule not to enter upon one on every casual opportunity, or except in accordance with a settled design, acted, it must be confessed, on this occasion with admirable generalship. He checked their flight when his men were near the camp, and forced them to halt and face about; but he sent out his aides and buglers to recall the rest, and prevented them from pursuing and engaging the enemy any more. So the Romans after a short halt went back, having killed a large number of the enemy, and lost very few themselves.