[SampleMan]

The Spanish brought, among other things, weapons, iron, steel, metal armor, the wheel and horses as well.

Yet, they were otherwise so massively outnumbered that the steel and firearms would have made little difference. I think the native help used to be discounted in order to enhance the glory of the feat and recently it has been ignored in order to demonize the feat.

[La Lydia]

I do not discount the native help the Spanish benefitted from, and indeed, think it was probably the deciding factor. But the technology they brought was also an important element. One of the advantages of their technology that had nothing to do with being outnumbered was its ability to stun, frighten and freeze the Aztecs, a kind of conquistadors’ shock and awe.

[allmendream]

A small military advantage can become a huge factor.

A cadre of 100 Spanish troops in armor with guns and swords could easily defeat 500 natives with stone-tip spears.

Once you reach that level of military advantage, all you need fear is a cadre of troops willing to engage in the cold calculus that enough of them could eventually wear you down and kill you all.

The natives didn't have any troops capable of withstanding that sort of carnage and a style of warfare they were absolutely unused to.

Look at Pizarro and Peru. 200 Spanish troops defeated an army of tens of thousands.

[anglian]

La Noche Triste ("the night of sorrows") on June 30, 1520 was an important episode during the Spanish conquest of Mexico wherein Hernán Cortés' conquest of the Aztec Empire was nearly halted in the Mexica capital at Tenochtitlan, and Cortés himself barely escaped. -wiki

Once you captured the leader (Moctezuma/Pizarro) it was the end. In the case of Moctezuma, hid own turned against him.

[Oatka]

The Spanish brought, among other things, weapons, iron, steel, metal armor, the wheel and horses as well.

A great read on that takeover is Bernal Diaz' "The Conquest of New Spain". Diaz was one of Cortez' men. The technology bit really blew my mind in a couple of places. Diaz reported (paraphrased) that when attacking the capital across those bridges, Captain X "took three crossbowmen and 3,000 Indian Auxiliaries to breach the position."

There was also a difference in approaches to battle - I understand that, like our Indians, fighting was very stylized and used mainly to obtain captives for sacrifice. On the other hand, the Conquistadors were one tough bunch. The standard treatment for cuts was to sear the wound with a red hot iron, then coat it with oil. In one instance they ran out of oil and Diaz says they cut open a dead Indian and used the body fat for the same purpose. No wonder they won.