Pancorbo had been regularly garrisoned; and to force the Ebro, with a numerous and efficient army occupying its banks, would have been equally tedious in operation, and uncertain in results. Wellington, with admirable skill, suddenly branched to his left, and moved rapidly towards the sources of the river; and, on the 14th and 15th, crossed it safely by the mountain bridges of San Martin and Puente de Arenas. Of course, the march, from the nearly impassable character of the line of country over which it ran, required the determination and _esprit_ of British soldiers to accomplish. It was gallantly achieved; and that too, by a route hitherto unattempted by an army, and which every where presented the most formidable positions that a retreating corps could wish to hold. Yet Wellington’s march was unopposed,--and until the 18th, no hostile collision interrupted the order of the allied movements. Two French brigades were overtaken by the light division. They had taken a position on the heights of Saint Milan; and although the ground was most unfavourable for an attack, nothing could surpass the dashing gallantry with which the British light troops assailed the enemy. The road by which it was necessary to attack, was rugged, steep, and narrow, overhung with crags and copse-wood; while a mountain stream protected the French front, and some straggling cottages increased the difficulty of advancing, by affording good cover to the voltigeurs formed behind them. After a sharp fusilade, the enemy gave ground, and the light brigade was pressing forward, when suddenly, a fresh column debouched from a ravine, and appeared on the flank of the assailants. Both rushed on to gain the crest of the hill--and both reached the plateau together. The 52nd, bringing their left flank forward in a run, faced sharply round, and charged with the bayonet. The conflict was but momentary; the French broke, threw away their knapsacks, and fled to gain the neighbouring high grounds, leaving their arms and baggage, and nearly three hundred of their number _hors de combat_. On the same day, Jourdan suddenly attacked Graham’s corps at Osma, but he was driven back on Espejo; and falling farther back, the French took up a strong position behind the Bayas, with their right on the village of Sabijana; but they held it only till next day,--when being attacked in front, and their left turned, they fell back and united the _corps d’armée_ in front of Vitoria.[219]