Although taken in flank, crushed under a storm of missiles, with their cavalry defeated and their centre broken, the Romans fought steadily and well. Hannibal now launched against their ranks the elephants attached to the infantry, which, covered in steel armour and trumpeting loudly, carried death and confusion into the Roman ranks. But still the legions fought on obstinately and desperately until the sound of wild music in their rear filled them with dismay, as Mago, with his division of Numidian infantry, emerged from his hiding place and fell upon the Romans from behind.
Struck with terror at the sudden appearance of these wild soldiers, of whose ferocity they had heard so much, the Romans lost all heart and strove now only to escape. But it was in vain. The Carthaginian infantry were in their front, the cavalry on their flank, the Numidians in their rear.
Some ten thousand Roman soldiers only, keeping in a solid body, cut their way through the cavalry and reached Piacenza.
Thirty thousand were slaughtered on the plain. Many were drowned in trying to swim the Trebia, and only the legion which had remained to guard the camp, the broken remains of the cavalry, and the body which had escaped from Piacenza remained of the fifty thousand men whom Sempronius commanded.
The exultation of the victors was unbounded. The hitherto invincible legions of Rome had been crushed. The way to Rome was clear before them. All the fatigues and hardships they had undergone were forgotten in the hour of triumph, and their native allies believed that their freedom from Rome was now assured.
The verdict of great commanders of all ages has assigned to the battle of the Trebia the glory of being the greatest military exploit ever performed. The genius of Hannibal was shown not only in the plan of battle and the disposition of his troops, but in the perfection with which they were handled, in the movements which he had himself invented and taught them, and the marvellous discipline with which he had inculcated them.
Napoleon the First assigned to Hannibal the leading place among the great generals of the world, and the Trebia was his masterpiece. But the Carthaginians, exulting in their victory, did not gauge the extent of the stubbornness and resources of Rome. Sempronius himself set the example to his countrymen. At Piacenza he rallied the remnants of his army, and wrote to Rome, saying that he had been victorious, but that a sudden storm had saved the enemy from destruction.
The senate understood the truth, but acted in the spirit in which he had written. They announced to the people that a victory had been won, and ordered the consular election to take place as usual, at the same time issuing orders to all parts of the Roman dominion for the enrolment of fresh troops.