在Ticinius落敗但仍然完整的羅馬軍撤退至特雷比亞河Trebia對岸,並在Placentia紮營等待與援軍會合。在Ticinius之役前,羅馬元老院早已傳令駐軍西西里島的執政官塞姆普羅紐斯·朗戈斯(Sempronius Longus)率軍趕回北方與西庇阿會合,聯合對付漢尼拔。
當年十二月,兩軍在特雷比亞Trebia河畔展開決戰,漢尼拔充分展現了他過人的軍事天才,運用騎兵騷擾羅馬軍營,誘使急躁的塞姆普羅紐斯下令全軍出擊,進入漢尼拔設下的陷阱。在雙方正面交鋒得如火如荼之際,迦太基伏兵從埋伏之處湧出,突襲羅馬軍側翼。羅馬兵潰不成軍,全軍傷亡超過三分之一。
1 Carthaginian camp Exact location unknown
2 Carthaginian cavalry 10,000 in all, 5,000 each wing? Elephants on each wing also.
3 Carthaginian infantry 20,000 heavy infantry supported by 8,000 light out front, falling back to wings.
4 Mago Barca's detachment 1,000 infantry, 1,000 cavalry
5 Trebbia river Schematic representation only.
6 Roman cavalry 4,000 in all, 2,000 each wing?
7 Roman infantry More than 38,000 in all: 18,000 Romans including 12,000 heavy and 6,000 light, 20,000 Italics, unknown number of Cenomani.
8 Roman camp Sempronius' camp. Scipio's camp was at Ripa Alta upstream.
9 Po river Approximation
0 City of Placentia (Piacenza) Approximation. Problem: the 20,000 Roman survivors were on left bank yet fell back on Piacenza.