When Hannibal encamped at the foot of the Alps, the CPO reached Etruria by sea and from there headed for the Alps. Here he understood the responsibilities of the Roman army. Under the CPO, Roman forces first crossed the Po River and advanced on its tributary, the Tricinus. Here, using a bridge built by the Romans, the CPO crossed the river and set up camp.
Hannibal has already come close. He went out with a large part of his cavalry to see firsthand the position of the opposing party. Meanwhile, the CPO left the Roman camp for the same reason. When the two groups met on the way, they quickly prepared to fight with the small army that was with them.
*Collision of Trisinus
Hannibal arranged the Spanish in the middle of his army and the Numidian cavalry a little behind on both sides. There were not enough cavalry with the CPO, but there were many infantrymen equipped with light weapons. He put them in front and put behind them a cavalry group made up of Gaul allies. Roman and Latin cavalry were kept as reserves.
Hannibal's cavalry attacked so hard that the Roman infantry had no time to use their weapons. Unaware of the direction, they fell on their cavalry behind them. While the cavalry warriors of the two groups were fighting each other, the Numidian armies dispersed the Roman infantry and attacked their cavalry from both sides.The CPO himself was injured at the time. According to Livy, her son rescues her and brings her to safety. This boy later became one of the best generals in Rome, the embodiment of Hannibal's defeat, CPO Africanus.
Seeing the state of the war strange, the Roman forces retreated under the direction of the CPO. By the time Hannibal arrived at the main Roman camp with full force, the CPO had retreated to Pleasantia. Because he realized that Carthage was in an advantageous position in the plains between Trisinas and Porus because of the majority of his cavalry.
Although Trisinus does not fall into the category of full-fledged war, it is of great importance. After this incident the surrounding Gaul tribes joined Hannibal's forces in groups. Moreover, through this battle Hannibal was able to establish a position of his own in this part of Italy, from where he planned to campaign against Rome.