The water was intensely cold, the river was in flood, the ford waist deep as the soldiers marched across it.  Having gained the opposite bank, the Roman general formed his army in order of battle.  His infantry, about forty-five thousand strong, was formed in three parallel lines; the cavalry, five thousand strong, was on the flanks.  The infantry consisted of sixteen thousand Roman legionary or heavy infantry, and six thousand light infantry.  The Italian tribes, allied to Rome, had supplied twenty thousand infantry; the remaining three thousand were native allies.  The infantry occupied a front of two and a half miles in length; the cavalry extended a mile and a quarter on each flank.  Thus the Roman front of battle was five miles in extent.

Hannibal’s force was inferior in strength; his infantry of the line were twenty thousand strong.  He had eight thousand light infantry and ten thousand cavalry.  The Carthaginian formation was much deeper than the Roman, and Hannibal’s line of battle was less than two miles long.  In front of it were the elephants, thirty-six in number, divided in pairs, and placed in intervals of a hundred yards between each pair.

While the Romans, exposed to a bitterly cold wind, chilled to the bone by their immersion in the stream, and having come breakfastless from camp, were forming their long order of battle, Hannibal’s troops, gathered round blazing fires, were eating a hearty breakfast; after which, in high spirits and confidence, they prepared for the fight.

Hannibal called the officers together and addressed them in stirring words, which were repeated by them to the soldiers.  The Roman preparations had occupied a long time, and it was afternoon before they advanced in order of battle.  When within a short distance of the Carthaginians they halted, and the trumpets and musical instruments on both sides blew notes of defiance.  Then the Carthaginian slingers stole out between the ranks of their heavy infantry, passed between the elephants, and commenced the battle.

Each of these men carried three slings, one of which was used for long distances, another when nearer to the foe, the third when close at hand.  In action one of these slings was wound round the head, one round the body, the third carried in hand.  Their long distance missiles were leaden bullets, and so skilful were they that it is said they could hit with certainty the face of a foe standing at slinging distance.

Naked to the waist they advanced, and with their long distance slings hurled the leaden bullets at the Roman infantry.  When closer they exchanged their slings and discharged from them egg shaped pebbles which they had gathered from the bed of the Trebia.  When within still closer distance with the third slings they poured in volleys of much larger and heavier stones, with such tremendous force that it seemed as though they were sent from catapults.  Against such a storm of missiles the Roman skirmishers could make no stand, and were instantly driven back.