At midnight the Spaniards and Tlaxcaltecas came out inclosed ranks, the Spaniards going first and the Tlaxcaltecas following. The allies kept very close behind, as if they were crowding up against a wall. The sky was overcast and rain fell all night in the darkness, but it was a gentle rain, more like a drizzle or a heavy dew.
The Spaniards carried portable wooden bridges to cross the canals. They set them in place, crossed over and raised them again. They were able to pass the first three canals-the Tecpantzinco, the Tzapotlan and the Atenchicalco-without being seen. But when they reached the fourth, the Mixcoatechialtitlan, their retreat was discovered.