Alvarado, with a portion of the cavalry, brought up the rear of the retreating army, in order to repel, with an occasional charge upon the enemy's ranks, those furious onsets which might have overwhelmed the small body of Spanish infantry, or the unmailed and lightly armed Tlascalan allies. The cavalier and his horse, encased in armor of proof, could better cope with the weapons and missiles of their assailants, while they often turned upon them, with a fierce and irresistible charge, trampling hundreds in the dust, and mowing down whole ranks on this side and that, with their trenchant broadswords. In this manner the fugitives defiled through the great southern avenue, and came out upon the grand causeway, by which they had twice entered the city. Here they were met by new and fresh squadrons of the enemy, thronging the sides of the dike in their light canoes, and showering down arrows thick as hail upon the advancing column. Sometimes keeping upon the causeway, they would grapple each with his man, and drag him off into the water, to be picked up by those in the canoes, and hurried off to a terrible and certain fate, on the great altar of their War-god. Their numbers increased every moment, till the lake was literally alive with them. At length the advancing column was brought to stand; while a cry of despair from the van revealed the fearful position in which they stood in the midst of their implacable foes. The bridges which intersected the dike had been removed by order of the Emperor. They had now reached the first opening thus made in the causeway. A sudden shout from the myriads of Aztec warriors that hung about them on all sides, told at once their own wild triumph, and the awfully perilous position of their enemy. Crowded together on a narrow causeway, in ranks so close as to render their arms and their weapons almost entirely useless--arrested in front by a wide chasm which it was impossible to pass--their retreat cut off in the rear, by the living masses that blocked up every avenue, and pressed them forward upon the crowded ranks of their comrades--assailed on both sides from the water, through the whole length of the closely compacted column--while all these dangers were enhanced a hundred-fold by the darkness of the night--there seemed no possibility of escape for one of that brave host. Cortez was with the principal part of the cavalry in the centre of the column, so wedged in by the compacted mass of his own forces, as to be quite unable either to advance or retreat, without trampling them under his feet, or crowding them off the causeway. He comprehended in a moment the perilous position he was in. But such was the utter confusion and dismay of the whole army, and such the horrid din of clashing arms, and the yet more horrid yells of the savage foe, that he in vain attempted either to direct or encourage his men. His voice was drowned in the uproar.