The advantage of position was all on the side of the United States army. The pass itself was so narrow that Washington’s battery could guard it against almost any force; impassable gullies and ravines flanked it on the west, and on the east the mountains gradually rose to a height of some two thousand feet. The only spot on which a regular battle could be fought was a plateau on the east of the pass, which stretched from the precipitous mountain-slope nearly to the road, terminating on that side in several ridges and ravines. This plateau gained, the pass might have been turned; and accordingly Santa Anna’s first thought was to master it. A strong body of light infantry was despatched, in the afternoon of the 22d, to climb the mountain-side which commanded the plateau; but the moment the manœuvre was perceived a party of Taylor’s riflemen ascended the opposite ridge to keep them in check. The Mexicans opened fire, and the Kentuckians replied; and thus, as each body strove to overtop the other, both ridges were soon covered with smoke. Foiled in his object, Santa Anna awaited the morning to commence operations in earnest; and Taylor, fearing an attack on Saltillo, set out to complete the defences of that point during the night. At two o’clock in the morning the American pickets were driven in, and at break of day the Mexican light infantry, on the ridge above the plateau, led by General Ampudia, commenced charging down into the ravine which separated them from the Kentuckians. They had received reinforcements during the night, and were at least eight to one. Fortunately, General Wool had anticipated the movement, and Lieutenant O’Brien was ready at the foot of the hill with a piece of cannon. A very few discharges, well-aimed, sent the Mexicans back to cover. Then the main army advanced; two columns, under Pacheco and Lombardini, supported by lancers and a twelve-pounder battery in the rear, marching directly toward the plateau, and a third moving against the pass. Wool had disposed the army almost in a line across the plateau from the pass to the mountain: Washington’s battery being on the right, and O’Brien’s on the left wing, the infantry and a squadron of dragoons in the centre, and the volunteer cavalry inclined slightly to the rear on the right and left. About nine in the morning Pacheco’s column debouched from a ravine and began to form coolly on a ridge of the plateau. General Lane hastened forward, skirting the mountains with the Second Indiana volunteers and O’Brien’s battery, to meet them. At two hundred yards O’Brien opened with terrific effect; the close columns of the Mexicans were ploughed by his shot. But the reply was steady and almost equally effective. Raked on the left by the twelve-pounder battery, and assailed by a storm of bullets from the masses rising out of the ravine, the volunteers fell thickly round their colors, and, after some minutes, the Indiana volunteers could stand it no longer, and