Hannibal's passage over the Alps is one of the most celebrated achievements of any military force in ancient warfare. Hannibal successfully crossed the Alps, despite numerous obstacles such as harsh climate and terrain, the guerrilla tactics of the native tribes, and the challenge of commanding an army diverse in race and language.
Hannibal's forces moved through the Po Valley and were engaged in a small confrontation at Ticinus. Here, Hannibal forced the Romans, by virtue of his superior cavalry, to evacuate the plain of Lombardy. While the victory was minor, it encouraged the Gauls and Ligurians to join the Carthaginian cause, whose troops bolstered his army back to 40,000 men. Scipio was severely injured and retreated across the river Trebia to camp at Placentia with his army intact.