Their first undertaking was to cut off the pipes that conducted the water from the royal streams of Chapoltepec to feed the numerous tanks and fountains which sparkled in the court-yards of the capital. The aqueduct, partly constructed of brickwork and partly of stone and mortar, was raised on a strong though narrow dike, which transported it across an arm of the lake; and the whole work was one of the most pleasing monuments of Mexican civilization. The Indians, well aware of its importance, had stationed a large body of troops for its protection. A battle followed, in which both sides suffered considerably, but the Spaniards were victorious. A part of the aqueduct was demolished, and during the siege no water found its way again to the capital through this channel.

On the following day the combined forces descended on the fatal causeway, to make themselves masters, if possible, of the nearest bridge. They found the dike covered with a swarm of warriors, as numerous as on the night of their disaster, while the surface of the lake was dark with the multitude of canoes. The intrepid Christians strove to advance under a perfect hurricane of missiles from the water and the land, but they made slow progress. Barricades thrown across the causeway embarrassed the cavalry and rendered it nearly useless. The sides of the Indian boats were fortified with bulwarks, which shielded the crews from the arquebuses and cross-bows; and, when the warriors on the dike were hard pushed by the pikemen, they threw themselves fearlessly into the water, as if it were their native element, and, reappearing along the sides of the dike, shot off their arrows and javelins with fatal execution. After a long and obstinate struggle, the Christians were compelled to fall back on their own quarters with disgrace, and—including the allies—with nearly as much damage as they had inflicted on the enemy. Olid, disgusted with the result of the engagement, inveighed against his companion as having involved them in it by his wanton temerity, and drew off his forces the next morning to his own station at Cojohuacan.

The camps, separated by only two leagues, maintained an easy communication with each other. They found abundant employment in foraging the neighboring country for provisions, and in repelling the active sallies of the enemy; on whom they took their revenge by cutting off his supplies. But their own position was precarious, and they looked with impatience for the arrival of the brigantines under Cortés. It was in the latter part of May that Olid took up his quarters at Cojohuacan; and from that time may be dated the commencement of the siege of Mexico.[417]