Meanwhile Sempronius, who had been recalled from Sicily, relieved the disabled Scipio.
Early one raw morning in December, 218, the vanguard of the Carthaginians was ordered to cross the Trebia, and, as soon any resistance was met, to retreat. The other troops of Hannibal were drawn up ready to give the enemy a hot reception, if, as he expected, they should pursue his retreating vanguard. Sempronius was caught in the trap, and all his army, except one division of 10,000, was cut to pieces. The survivors took refuge in Placentia and Cremona, where they spent the winter. Sempronius himself escaped to Rome.
The result of TREBIA was the insurrection of all the Celtic tribes in the valley of the Po, who increased Hannibal's army by 60,000 infantry and 4,000 cavalry. While the Carthaginian was wintering near Placentia, the Romans stationed troops to guard the two highways leading north from Rome and ending at Arretium and Ariminum, The Consuls for this year were GAIUS FLAMINIUS and GNAEUS SERVILIUS. The former occupied Arretium, the latter Ariminum. Here they were joined by the troops that had wintered at Placentia.
In the spring, Hannibal, instead of attempting to pursue his march by either of the highways which were fortified, outflanked the Romans by turning aside into Etruria. His route led through a marshy and unhealthy country, and many soldiers perished. Hannibal himself lost an eye from ophthalmia. When he had arrived at Faesulae a report of his course first reached Flaminius, who at once broke camp and endeavored to intercept his enemy. Hannibal, however, had the start, and was now near LAKE TRASIMÉNUS.
Here was a pass with a high hill on one side and the lake on the other. Hannibal, with the flower of his infantry, occupied the hill. His light-armed troops and horsemen were drawn up in concealment on either side.
The Roman column advanced (May, 217), without hesitation, to the unoccupied pass, the thick morning mist completely concealing the position of the enemy. As the Roman vanguard approached the hill, Hannibal gave the signal for attack. The cavalry closed up the entrance to the pass, and at the same time the mist rolled away, revealing the Carthaginian arms on the right and left. It was not a battle, but a mere rout. The main body of the Romans was cut to pieces, with scarcely any resistance, and the Consul himself was killed. Fifteen thousand Romans fell, and as many more were captured. The loss of the Carthaginians was but 1,500, and was confined mostly to the Gallic allies. All Etruria was lost, and Hannibal could march without hindrance upon Rome, whose citizens, expecting the enemy daily, tore down the bridges over the Tiber and prepared for a siege. QUINTUS FABIUS MAXIMUS was appointed Dictator.
Hannibal, however, did not march upon Rome, but turned through Umbria, devastating the country as he went. Crossing the Apennines, he halted on the shores of the Adriatic, in Picénum. After giving his army a rest, he proceeded along the coast into Southern Italy.
The Romans, seeing that the city was not in immediate danger, raised another army, and placed the Dictator in command. Fabius was a man of determination and firmness, well advanced in years. He determined to avoid a pitched battle, but to dog the steps of the enemy, harassing him and cutting off his supplies as far as possible.
Meanwhile Hannibal again crossed the mountains into the heart of Italy to Beneventum, and from there to Capua, the largest Italian city dependent upon Rome. The Dictator followed, condemning his soldiers to the melancholy task of looking on in inaction, while the enemy's cavalry plundered their faithful allies. Finally, Fabius obtained what he considered a favorable opportunity for an attack. Hannibal, disappointed in his expectations that Capua would be friendly to him, and not being prepared to lay siege to the town, had withdrawn towards the Adriatic. Fabius intercepted him near Casilinum, in Campania, on the left bank of the Volturnus. The heights that commanded the right bank of the river were occupied by his main army; and the road itself, which led across the river, was guarded by a strong division of men.
Hannibal, however, ordered his light-armed troops to ascend the heights over the road during the night, driving before them oxen with burning fagots tied to their horns, giving the appearance of an army marching by torchlight. The plan was successful. The Romans abandoned the road and marched for the heights, along which they supposed the enemy were going. Hannibal, with a clear road before him, continued his march with the bulk of his army. The next morning he recalled his light-armed troops, which had been sent on to the hills with the oxen. Their engagement with the Romans had resulted in a severe loss to Fabius.