The Battle of the Trebia was the first major battle of the Second Punic War, fought between the Carthaginian forces of Hannibal and a Roman army under Sempronius Longus on 22 or 23 December 218 BC. Each army had a strength of about 40,000 men; the Carthaginians were stronger in cavalry, the Romans in infantry. The battle took place on the flood plain of the west bank of the lower Trebia River, not far from the settlement of Placentia, and resulted in a heavy defeat for the Romans.