one o'clock on July 1st, 1520
This was a most faulty arrangement , necessitating frequent and long delays , and entailing almost certain disaster . Had three such portable bridges been constructed , the column could have crossed the causeway with comparatively little risk ; and there was no reason why these bridges should not have been constructed , as they could have been carried , without difficulty , by the Tlascalans . At midnight the troops were in readiness for the march . Mass was performed by Father Olmedo ; and at one o'clock on July 1st , 1520 , the Spaniards sallied out from the fortress that they had so stoutly defended . Silence reigned in the city . As noiselessly as possible , the troops made their way down the broad street , expecting every moment to be attacked ; but even the tramping of the horses , and the rumbling of the baggage wagons and artillery did not awake the sleeping Mexicans , and the head of the column arrived at the head of the causeway before they were discovered . Then , as the advanced guard were preparing to lay the portable bridge across the first opening , some Aztec sentinels gave the alarm .