People think that after Cortez reached Tenotchitlan (or whatever) that he had it made; that the Aztec struggle was all over and the Atzecs were finished.
Cortez and his men for a short time in fact got thrown out, had to retreat, and there was tons of fighting.
Battle of The Dismal Night
Cortez had lost a lot of men, they were fighting everyone, a bit like an ancient, taco version of Blackhawk Down, and they finally got a short respite when the haggard men were going threw a narrow draw that afforded protection on their flanks.
It was, “God Sez to Kill a Spaniard Day”.
When Cortez emerged from the protection of the draw they found an Aztec army of 200,000 Aztec warriors just waiting to devour them. They were totally exhausted seeing this —the situation seemed hopeless.
You know that weird, yuge umbrella thing you always see the Aztecs waving around on top of the sacrificial temples? Has feathers on it, and it’s God’s Magic status standard bearer, or something. I’m sure there’s some fancy Aztec word for it.
It was a super important symbol of Aztec authority.
Cortez decided as long as they were going to die that they might as well Go Out With Style.
The men all summoned up their last bits of strength, charged like mad-men into the endless mass of warriors. Lo and behold they got deep enough that they found they were face-to-face with the painted-up guys with the yuge Aztec Umbrella thingy, which they captured:
That had a magical effect.
Everyone was dumbfounded, and they broke and ran, so symbolic was Cortez’ act of capturing that sacred, fancy Umbrella.
Cortez’ men were saved and resistance to them totally collapsed, the Aztecs were finished and all serving as slaves to them joined the side of Cortez.
The battle of Otumba.
This was fought and won entirely hand-to-hand, with cold steel. A few horsemen, however, were decisive. The Aztecs hadn’t figured out, yet, how to deal with cavalry.
The conquistadors did not win with high tech, this is rarely understood. They had only a very marginal technological advantage.