When Cortes brought out his fleet of brigantines upon the lake, he went in the first place to attack an insular rock close beside Mexico, on which a vast number of the inhabitants of that city and other places in the neighbourhood had taken shelter. Immediately on perceiving his intentions, their whole force collected from every part of the lake, and proceeded against him in not less than 4000 large canoes full of warriors. On perceiving this immense number of boats coming to attack him, Cortes withdrew with his brigantines into an open part of the lake, ordering his captains to wait patiently for a breeze of wind which then began to blow. As the enemy supposed that this movement proceeded from fear, they immediately closed up around the flotilla with shouts of triumph. The wind now sprung up, and the whole fleet made sail through the throng of canoes, plying their oars at the same time, and run down and overset great numbers of the Mexican canoes, compelling all the rest to fly for shelter to the recesses and shallows on the borders of the lake. After this, Cortes made sail to Cojohuacan56, where he was again attacked by the Mexicans, both by means of their canoes on the water, and from their temples on the land: But Cortes brought four guns to bear upon them, by which he did considerable execution. During this action his powder magazine blew up, owing to some mismanagement of the gunners, by which many of his people were wounded. This unfortunate accident obliged him to detach his smallest brigantine to Sandoval for a supply of ammunition. He remained at Cojohuacan for two days with the flotilla, repairing the injury his ship had sustained from the explosion.

When we were assured that the flotilla was out upon the lake, Alvarado marched out with our division to the causeway of Tacuba, as far as the bridge, in which we were constantly engaged with the enemy to very little purpose, except that we repaired the passes in our rear as we advanced, and did not now suffer the cavalry to come upon the causeway, as we had found by experience that they were of very little service, and besides that their horses were exposed to much danger. Finding that he could not sufficiently annoy the enemy in his present post at Iztapalapa, where the Mexicans had possession of the houses which were built in the water, Sandoval advanced by a causeway to a more commanding situation57. When this was noticed from Mexico, a large detachment of warriors came over in canoes, with orders to cut the causeway in the rear of our troops. Cortes observed this, and immediately made sail with his vessels to the relief of Sandoval, giving orders at the same time to De Oli to march a body of troops by the causeway for the same purpose. Having relieved Sandoval by these means, Cortes ordered him to remove with his division from Iztapalapa to Tepeaquilla or Tepejacac, where the church of our Lady of Guadalupe now stands, in which many wonderful miracles have been performed.

As it was impossible for our troops to advance on the causeways, unless their flanks were secured from attacks by water, the flotilla was appointed to this service in three divisions, one of which was attached to each of the three detachments of our land force: Four brigantines being allotted to Alvarado, six to De Oli, and two to Sandoval58; twelve in all, the thirteenth having been found too small for service, and was therefore laid up, and her crew distributed to the rest, as twenty men had been already severely wounded in the several vessels. Alvarado now led our division to attack the causeway of Tacuba, placing two brigantines on each flank for our protection. We drove the enemy before us from several of their bridges and barricades; but after fighting the whole day, we were obliged to retreat to our quarters at night, almost all of us wounded by the incessant showers of stones and arrows of the enemy. We were continually assailed on the causeway, by fresh troops of warriors, carrying different banners or devices; and our brigantines were excessively annoyed from the terraces of the houses which stood in the water; and as we could not leave a party to keep possession of what we had acquired during the day, the enemy repossessed themselves of the bridges at night, and repaired and strengthened their parapets and other defences. In some places they deepened the water, digging pits in the shallow places, and placing the canoes in ambush, which they secured against the approach of our brigantines by means of pallisades under water. Every day we were employed in the same manner, driving the enemy before us, and every night we returned to our quarters to bind up our wounds. The cavalry were of no service, on account of the barricades defended by long lances; and the soldiers even did not choose to risk their horses, as their price at this time was from eight hundred to a thousand crowns. One Juan, a soldier from Catalonia, used to heal our wounds by charms and prayers, which by the mercy of God recovered us very fast; and this being observed by our allies, all their wounded men applied to Juan, who had more business on his hands than he was able for. But whether whole or wounded, we were obliged to go out daily against the enemy, as otherwise our companies would have been reduced to less than half their strength. Our ensign was disabled almost every day, as he could not at the same time carry his colours and defend himself from the enemy. We were abundantly supplied with corn, but were much in want of refreshments for the wounded men; our chief resource being tunas or Indian figs, cherries while in season, and a plant called quilities by the natives. The situation of the other two attacks was precisely similar to ours. Every day, when we marched to the attack, a signal was made from the great temple of Tlaltelolco, the great division of Mexico nearest Tacuba, on which the enemy rushed out against us, and were continually relieved by fresh troops, marching out in succession. Finding that we gained nothing by these daily attacks, we changed our plan of operations. On our causeway there was a small open space, on which stood some buildings for religious worship, where we formed a lodgment, and established a post, leaving our cavalry and allies to secure our rear in Tacuba, whence we were supplied with provisions. Though very badly lodged in this place, as every shower of rain came in upon us, we maintained this post and advanced a little towards the city every day, filling up the trenches which intersected the causeway, and pulling down the houses on each side, and using their materials to strengthen our defences. We found it extremely difficult to set the houses on fire, nor could the flames communicate from house to house, as all the houses were separated by canals and ditches. During this operation we were subjected to great danger, as the enemy destroyed us from their terraces when we endeavoured to swim over from the causeway to these detached houses.

In this manner we gained some ground every day, which we secured by parapets and other defences, and preserved during the night. Every evening at sunset, the company which was first for duty, was entrusted with the advanced post, to which they sent forty men; the second company sent an equal number at midnight, and the relieved guard did not quit their post, but had to remain sleeping on the ground; the third company did the same the same two hours before day-break, and the second now lay down to sleep, so that we now had 120 men on guard. Sometimes our whole detachment had to remain under arms the whole night, especially on the following occasion: We learnt from some of our prisoners, that the Mexicans intended to force our post by a great effort, which would have frustrated the other two attacks. For this purpose, all the warriors of nine towns around the lake, including those of Tacuba, Izcapuzalco, and Tenajocan, were by a joint attack upon our rear to carry off our baggage and destroy our bakery in Tacuba, while the Mexicans were to assail us in front on the causeway. We immediately communicated this intelligence to our cavalry and allies at headquarters, warning them to keep on the alert. In pursuance of this plan, we were attacked both in front and rear for several successive nights, from midnight to day-break. Sometimes the enemy came on with a prodigious noise of shouting and military instruments, and at other times stole upon us in profound silence; but their night attacks were never made with so much resolution as those during the day. Yet we were harassed to death with continual watching, fatigue, and wounds, and constantly exposed to cold winds and almost incessant rain. Our post was reduced to a mere splash of mud and water, and our only food was maize and miserable herbs. When we complained, the only comfort given us by our officers, was that such is the fortune of war. Yet all our efforts, fatigues, and privations, were of little avail; as the parapets we destroyed and the ditches we filled up during the day, were uniformly replaced next night by the enemy.