“Nature and art had rendered the ground from Calhandriz to the river particularly strong; but to make the defences still more formidable, and to form an intermediate obstruction, redoubts were thrown up extending to the rear, nearly at right angles with the front line. These swept the whole portion of the valley, by which a column of infantry must penetrate, even had it succeeded in forcing an entrance into the ravine. Sixty-nine works of different descriptions fortified this line; in these were mounted three hundred and nineteen pieces of artillery, requiring upwards of eighteen thousand men to garrison them; and the extent, in a direct line from flank to flank, was twenty-five miles.” Colonel Leith Hay explains the mode in which those formidable lines would have been defended. “It has been erroneously supposed that the regular army was, in the event of an attack, to occupy the redoubts and other works in the lines, or, at all events, that a large proportion of the troops would of necessity defend these temporary fortifications. In this calculation of probable circumstances, no British soldiers, with the exception of artillery, would have acted within their walls. Some Portuguese infantry, with the militia and ordonanza, were destined to compose the garrisons; while the whole allied army, numerous, brilliant in equipment, high in spirit, confident in its great commander, was prepared to move in every direction to cover the summits of mountains, to descend into valleys, or to pour in torrents on any luckless column, that with diminished numbers might have forced past the almost impenetrable obstacles of this grand position.”