around the northern head of the lake of Tezcoco, whilst Sandoval, supported by Cortéz with the brigantines, passed around the southern portion of it, to complete the destruction of the town of Iztapalapan, which was deemed by the conqueror altogether too important a point to be left in the rear. In the latter part of May, 1521, all these cavaliers got into their assigned military positions, and it is from this period that the commencement of the siege of Mexico is dated, although Alvarado had previously had some conflicts with the people on the causeway that led to his head quarters in Tacuba, and had already destroyed the pipes that fed the water-tanks and fountains of the capital.
At length Cortéz set sail with his flotilla in order to sustain Sandoval's march to Iztapalapan. As he passed across the lake and under the shadow of the "rock of the Marquis," he descried from his brigantines several hundred canoes of the Mexicans filled with soldiers and advancing rapidly over the calm lake. There was no wind to swell his sails or give him command of his vessels' motion, and the conqueror was obliged to await the arrival of the canoes without making such disposition for action as was needful in the emergency. But as the Indian squadron approached, a breeze suddenly sprang up, and Cortéz, widening his line of battle, bore down upon the frail skiffs, overturning, crushing and sinking them by the first blow of his formidable prows, whilst he fired to the right and left amid the discomfitted flotilla. But few of these Indian boats returned to the canals of the city, and this signal victory made Cortéz, forever after, the undisputed master of the lake.
The conqueror took up his head quarters at Xoloc, where the causeway of Cojohuacan met the great causeway of the south. The chief avenues to Mexico had been occupied for some time, as has been already related, but either through ignorance or singular neglect, there was the third great causeway, of Tepejacac, on the north, which still afforded the means of communication with the people of the surrounding country. This had been altogether neglected. Alvarado was immediately ordered to close this outlet, and Sandoval took up his position on the dyke. Thus far the efforts of the Spaniards and auxiliaries had been confined to precautionary movements rather than to decisive assaults upon the capital. But it soon became evident that a city like Mexico might hold out long against a blockade alone. Accordingly an attack was ordered by Cortéz to be made by the two commanders at the other military points nearest their quarters. The brigantines sailed
