By eleven--hardly seven hours having elapsed since the Contreras camp had been stormed, five miles away--Twiggs and Pillow were in motion toward the San Antonio causeway. Nothing had been heard of Worth, who had been directed to move along the east side of the Pedregal on San Antonio; but it was taken for granted he had carried the point, and Scott wished to cut off the retreat of the garrison. Twiggs was advancing cautiously toward the convent, when a heavy firing was heard in advance. Supposing that a reconnoitring party had been attacked, he hastily sent forward the First Artillery, under Dimmick, through a field of tall corn, to support them. No sooner had they separated from the main body than a terrific discharge of grape, canister, and musketry assailed them from the convent. In the teeth of the storm they advanced to within one hundred yards of that building, and a light battery under Taylor was brought up on their right and opened on the convent. Over an hour the gunners stood firm to their pieces under a fire as terrible as troops ever endured; one-third of the command had fallen before they were withdrawn. Colonel Riley meanwhile, with the stormers of Contreras, had been despatched to assail San Pablo on the west, and, like Dimmick, was met by a murderous rain of shot. Whole heads of companies were mowed down at once. Thus Captain Smith fell, twice wounded, with every man beside him; and a single discharge from the Mexican guns swept down Lieutenant Easley and the section he led. It was the second time that day the gallant Second had served as targets for the Mexicans, but not a man fell back. General Smith ordered up the Third in support, and these, protecting themselves as best they could behind a few huts, kept up a steady fire on the convent. Sallies from the works were constantly made and as constantly repulsed, but not a step could the assailants make in advance. By this time the battle was raging on three different points. Worth had marched on San Antonio that morning, found it evacuated, and given chase to the Mexicans with the Fifth and Sixth Infantry. The causeway leading from San Antonio to the _tête de pont_ of Churubusco was thronged with flying horse and foot; our troops dashed headlong after them, never halting till the advance corps--the Sixth--were within short range of the Mexican batteries. A tremendous volley from the _tête de pont_ in front and the convent on the flank then forced them to await the arrival of the rest of the division. This was the fire which Twiggs heard when he sent Dimmick against the convent.