Since Sandoval will not be able to render efficient service on his route for an attack on Tlatelulco, he is ordered to join Alvarado with the weightiest part of his forces, and to take advantage of the movement to entrap the Mexicans.
He will pretend to make a general evacuation of his camp, and thus allure the foe to an attack on the baggage-train, during which the ambuscaded cavalry can inflict a lesson which shall also serve to secure the camp against later attack.
Sandoval sends another portion of his forces to Cortés, who has more points to cover, and receives instructions to attend in particular to the capture of the channels and their filling, and otherwise to secure the safety of the more impetuous Alvarado.
On the day appointed, the brigantines with their flotillas are sent early to aid in clearing the causeways and approaches. The troops find little trouble in
reaching the Tlacopan avenue, from which three long roads give access to the market. It is advantageous to push the advance on each of these, and three divisions are accordingly formed, one to follow the main street under command of the comptroller and treasurer, Julian de Alderete, who has been among the foremost to urge the assault; another under Andrés de Tápia and Jorge de Alvarado, brother of the Tlacopan leader, both dashing and able men; the third and somewhat larger body, swelled particularly by auxiliaries, Cortés himself directs along the most dangerous approach, a sort of causeway, lined with houses but bordered with water.20 Two cannon are placed on the Tlacopan road, guarded by eight horsemen, and Cortés leaves his horse at the entrance of the road taken by him, and gives strict orders to all captains for filling every channel behind them.