Scipio now started in the utmost haste with all his troops for Avignon; but, when he arrived there, even the Carthaginian cavalry that had been left behind to cover the passage of the elephants had already taken its departure three days ago, and nothing remained for the consul but to return with weary troops and little credit to Massilia, and to revile the "cowardly flight" of the Punic leader. Thus the Romans had for the third time through pure negligence abandoned their allies and an important line of defence; and not only so, but by passing after this first blunder from mistaken slackness to mistaken haste, and by still attempting without any prospect of success to do what might have been done with so much certainty a few days before, they let the real means of repairing their error pass out of their hands. When once Hannibal was in the Celtic territory on the Roman side of the Rhone, he could no longer be prevented from reaching the Alps; but if Scipio had at the first accounts proceeded with his whole army to Italy--the Po might have been reached by way of Genoa in seven days--and had united with his corps the weak divisions in the valley of the Po, he might have at least prepared a formidable reception for the enemy. But not only did he lose precious time in the march to Avignon, but, capable as otherwise he was, he wanted either the political courage or the military sagacity to change the destination of his corps as the change of circumstances required. He sent the main body under his brother Gnaeus to Spain, and returned himself with a few men to Pisae.
Hannibal's Passage Of The Alps
Hannibal, who after the passage of the Rhone had in a great assembly of the army explained to his troops the object of his expedition, and had brought forward the Celtic chief Magilus himself, who had arrived from the valley of the Po, to address the army through an interpreter, meanwhile continued his march to the passes of the Alps without obstruction. Which of these passes he should choose, could not be at once determined either by the shortness of the route or by the disposition of the inhabitants, although he had no time to lose either in circuitous routes or in combat. He had necessarily to select a route which should be practicable for his baggage, his numerous cavalry, and his elephants, and in which an army could procure sufficient means of subsistence either by friendship or by force; for, although Hannibal had made preparations to convey provisions after him on beasts of burden, these could only meet for a few days the wants of an army which still, notwithstanding its great losses, amounted to nearly 50,000 men. Leaving out of view the coast route, which Hannibal abstained from taking not because the Romans barred it, but because it would have led him away from his destination, there were only two routes of note leading across the Alps from Gaul to Italy in ancient times:(3) the pass of the Cottian Alps (Mont Genevre) leading into the territory of the Taurini (by Susa or Fenestrelles to Turin), and that of the Graian Alps (the Little St. Bernard) leading into the territory of the Salassi (to Aosta and Ivrea). The former route is the shorter; but, after leaving the valley of the Rhone, it passes by the impracticable and unfruitful river-valleys of the Drac, the Romanche, and the upper Durance, through a difficult and poor mountain country, and requires at least a seven or eight days' mountain march. A military road was first constructed there by Pompeius, to furnish a shorter communication between the provinces of Cisalpine and Transalpine Gaul.
The route by the Little St. Bernard is somewhat longer; but after crossing the first Alpine wall that forms the eastern boundary of the Rhone valley, it keeps by the valley of the upper Isere, which stretches from Grenoble by way of Chambery up to the very foot of the Little St. Bernard or, in other words, of the chain of the higher Alps, and is the broadest, most fertile and most populous of all the Alpine valleys. Moreover, the pass of the Little St. Bernard, while not the lowest of all the natural passes of the Alps, is by far the easiest; although no artificial road was constructed there, an Austrian corps with artillery crossed the Alps by that route in 1815. And lastly this route, which only leads over two mountain ridges, has been from the earliest times the great military route from the Celtic to the Italian territory. The Carthaginian army had thus in fact no choice. It was a fortunate coincidence, but not a motive influencing the decision of Hannibal, that the Celtic tribes allied with him in Italy inhabited the country up to the Little St. Bernard, while the route by Mont Genevre would have brought him at first into the territory of the Taurini, who were from ancient times at feud with the Insubres.
So the Carthaginian army marched in the first instance up the Rhone towards the valley of the upper Isere, not, as might be presumed, by the nearest route up the left bank of the lower Isere from Valence to Grenoble, but through the "island" of the Allobroges, the rich, and even then thickly peopled, low ground, which is enclosed on the north and west by the Rhone, on the south by the Isere, and on the east by the Alps. The reason of this movement was, that the nearest route would have led them through an impracticable and poor mountain- country, while the "island" was level and extremely fertile, and was separated by but a single mountain-wall from the valley of the upper Isere. The march along the Rhone into, and across, the "island" to the foot of the Alpine wall was accomplished in sixteen days: it presented little difficulty, and in the "island" itself Hannibal dexterously availed himself of a feud that had broken out between two chieftains of the Allobroges to attach to his interests one of the most important of the chiefs, who not only escorted the Carthaginians through the whole plain, but also supplied them with provisions, and furnished the soldiers with arms, clothing, and shoes.