In the spring of 218 Hannibal started from Carthágo Nova to invade Italy. His army consisted of 90,000 infantry, 12,000 cavalry, and 37 elephants. His march to the Pyrenees occupied two months, owing to the opposition of the Spanish allies of Rome. Hannibal now sent back a part of his troops, retaining 50,000 infantry and 9,000 cavalry, all veterans. With these he crossed the mountains, and marched along the coast by Narbo (Narbonne) and Nemansus (Nîmes), through the Celtic territory, with little opposition. The last of July found him on the banks of the Rhone, opposite Avenio (Avignon). The Romans were astonished at the rapidity of his movements.

The Consuls of the year were SCIPIO and SEMPRONIUS. The former had been in Northern Italy, leisurely collecting forces to attack Hannibal in Spain; the latter was in Sicily, making preparations to invade Africa. Scipio set sail for Spain, touching at Massilia near the end of June. Learning there for the first time that Hannibal had already left Spain, he hoped to intercept him on the Rhone. The Celtic tribes of the neighborhood were won over to his side. Troops collected from these were stationed along the river, but Scipio's main army remained at Massilia. It was Hannibal's policy to cross the river before Scipio arrived with his troops. He obtained all the boats possible, and constructed numerous rafts to transport his main body of troops. A detachment of soldiers was sent up the river with orders to cross at the first available place, and, returning on the opposite bank, to surprise the Celtic forces in the rear. The plan succeeded. The Celts fled in confusion, and the road to the Alps was opened. Thus Scipio was outgeneralled in the very beginning.

His course now should have been to return to Northern Italy with all his forces, and take every means to check Hannibal there. Instead, he sent most of his troops to Spain under his brother Gnaeus Scipio, and himself, with but a few men, set sail for Pisae.

Meanwhile Hannibal hurried up the valley of the Rhone, across the Isara, through the fertile country of the Allobroges, arriving, in sixteen days from Avenio, at the pass of the first Alpine range (Mont du Chat). Crossing this with some difficulty, owing to the nature of the country and the resistance of the Celts, he hastened on through the country of the Centrónes, along the north bank of the Isara. As he was leaving this river and approaching the pass of the Little St. Bernard, he was again attacked by the Celts, and obliged to make the ascent amidst continual and bloody encounters. After toiling a day and a night, however, the army reached the summit of the pass. Here, on a table-land, his troops were allowed a brief rest.

The hardships of the descent were fully as great, and the fertile valley of the Po was a welcome sight to the half-famished and exhausted soldiers. Here they encamped, in September, and recruited their wearied energies.

This famous march of Hannibal from the Rhone lasted thirty-three days, and cost him 20,000 infantry and 3,000 cavalry.

The Romans were still unprepared to meet Hannibal. One army was in Spain under Gnaeus Scipio; the other in Sicily, on its way to Africa, under the Consul Sempronius. The only troops immediately available were a few soldiers that had been left in the valley of the Po to restrain the Gauls, who had recently shown signs of defection.

Publius Cornelius Scipio, upon his return from Massilia, took command of these. He met Hannibal first in October, 218, near the river Ticinus, a tributary of the Po. A cavalry skirmish followed, in which he was wounded and rescued by his son, a lad of seventeen, afterwards the famous Africanus. The Romans were discomfited, with considerable loss.

They then retreated, crossing the Po at Placentia, and destroying the bridge behind them. Hannibal forded the river farther up, and marched along its right bank until he reached its confluence with the Trebia, opposite Placentia. Here he encamped.

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.