How close did Cortés actually come to losing everything in 1520?
I've been going back over the numbers of the conquest and the June-July 1520 stretch keeps bothering me. Cortés loses half his army in the canals on the night of June 30th. The only reason he survives is that the Aztec pursuit stops at the city edge. Even then he can't return until smallpox has gutted the city, and 1521 only works because of Tlaxcala.
For people who've read deeper on this period: was there a point where the Spanish side was simply done? If Cuitláhuac orders the pursuit to continue and finishes them on the road to Tlaxcala, is that it? No 1521, no Peru, no Potosí?
Or was it already over the moment smallpox landed, no matter what happened to Cortés?