On the 16th the vanguard, under Lannes, reached the beautiful vale of Aosta, and the other divisions descended rapidly on their footsteps. This part of the progress was not less difficult than the ascent before. The horses, mules, and guns, were to be led down one slippery steep after another—and we may judge with what anxious care, since Napoleon himself was once contented to slide nearly a hundred yards together, seated.
On the 17th Lannes arrived at Chatillon, where he attacked and defeated a corps of 5000 Austrians—who received the onset of a French division in that quarter, with about as much surprise as if an enemy had dropped on them from the clouds. Every difficulty now seemed to be surmounted, and corps after corps came down into the plentiful and verdant valley, full of joy. But suddenly the march of the vanguard was arrested by an obstacle unforeseen, or, at least, grievously under-estimated. Midway between Aosta and Ivrea the Dora flows through a defile, not more than fifty yards in width: the heights on either hand rise precipitous; and in the midst an abrupt conical rock, crowned with the fortress of St. Bard, entirely commands the river, and a small walled town, through the heart of which lies the only passage. Lannes having vainly attempted to force the place by a coup de main, a panic arose, and this spreading to the rear, orders were given for stopping the descent of the artillery. The Consul had come as far as the town of Aosta when this intelligence reached him. He immediately hastened to St. Bard, where he found the troops in much confusion.