+50.+ Having in ten days’ march accomplished a distance of eight hundred stades along the river bank, Hannibal began the ascent of the Alps,[180] and immediately found himself involved in the most serious dangers. For as long as the Carthaginians were on the plains, the various chiefs of the Allobroges refrained from attacking them from fear of their cavalry, as well as of the Gauls who were escorting them. But when these last departed back again to their own lands, and Hannibal began to enter the mountainous region, the chiefs of the Allobroges collected large numbers of their tribe and occupied the points of vantage in advance, on the route by which Hannibal’s troops were constrained to make their ascent. If they had only kept their design secret, the Carthaginian army would have been entirely destroyed: as it was, their plans became known, and though they did much damage to Hannibal’s army, they suffered as much themselves. For when that general learnt that the natives were occupying the points of vantage, he halted and pitched his camp at the foot of the pass, and sent forward some of his Gallic guides to reconnoitre the enemy and discover their plan of operations. The order was obeyed: and he ascertained that it was the enemy’s practice to keep under arms, and guard these posts carefully, during the day, but at night to retire to some town in the neighbourhood. Hannibal accordingly adapted his measures to this strategy of the enemy. He marched forward in broad daylight, and as soon as he came to the mountainous part of the road, pitched his camp only a little way from the enemy. At nightfall he gave orders for the watch-fires to be lit; and leaving the main body of his troops in the camp, and selecting the most suitable of his men, he had them armed lightly, and led them through the narrow parts of the road during the night, and seized on the spots which had been previously occupied by the enemy: they having, according to their regular custom, abandoned them for the nearest town. [Sidenote: The Gauls harass the army.]