On gaining the frontier, Graham secured his communication with the Gallician corps under Giron. The French retired, from the Esla, and the left wing of the British crossed it on the 31st of May. A difficult and defensible river was thus safely passed--and the enemy retreated, after blowing up the bridges of Zamora and Toro. At Morales, the French rear-guard, was overtaken and brought to action. Colonel Grant, with the hussar brigade, completely overthrew it,--killing a considerable number and capturing above two hundred men. Julian Sanchez was equally successful--he having surprised a French picket at Castronuno. No movements executed during the Peninsular campaign exceeded in brilliant effect the rapid advance of the allied army from the Douro to the Bayas. Joseph had been obliged to abandon the capital, and fall back on Burgos. This was a necessary measure to ensure a concentration of his _corps d’armée_,--but still, it was considered doubtful whether Lord Wellington would continue his onward march, and under all circumstances, actually become assailant. But the French leaders were astray when they fancied that the allied general would remain inactive. Quickly as the Douro had been crossed, the Carrion and the Pisuerga were as rapidly passed over. The enemy fell back on Burgos to concentrate, having occupied the heights above Harmoza with a strong corps. On the 12th, Hill’s division and the cavalry obliged Count Reille to fall back--and on the next morning the French retreated on Miranda, after abandoning Burgos and blowing up the castle.[217] “It can hardly be imagined what additional interest even a brilliant operation will acquire from local circumstances, and the character of the country through which the line of march runs. The advance to the Zadorra exhibited, at every point of view, scenery beautiful as diversified. In it there was a singular combination of romantic wildness mingled with exquisite fertility. One while the columns moved through luxurious valleys, intersprinkled with hamlets, vineyards, and flower-gardens; at another, they struggled up mountain ridges, or pressed through alpine passes overhung with topping cliffs, making it almost difficult to decide, whether the rugged chasm which they were traversing had been rifted from the hill-side by an earthquake, or scarped by human hands. If the eye turned downwards, there lay sparkling rivers and sunny dells; above rose naked rocks and splintered precipices; while moving masses of glittering soldiery, now lost, now seen, amid the windings of the route, gave a panoramic character to the whole, that never can fade from the memory of him who saw it.”[218]