The story I was always taught is that the Spanish conquistadors rolled over the Aztecs, Maya, and Incas in what would be an inevitable victory chalked up to guns, germs, and steel. But I always found this conclusion a bit smelly. Sure the Spanish had guns and horses, but they didn't have very many of them (a few hundred) and they were not very good. Three and a half centuries later, the US struggled at times in its wars with North American tribes (just ask the Custer family) despite having FAR better guns, many more trained troops (just after the Civil War), numerical superiority rather than inferiority, and a much better logistics situation (land access by rail vs. sea access by wooden boat). In addition, Latin American civilizations faced by the Spanish were better organized, far more numerous, and technologically more advanced than plains Indians. So why the seemingly easy victory by the Spanish?
Apparently there is a new book discussing this topic, which claims the results were much more contingent than commonly believed.
The “steel and germs” explanation for the rapidity of conquest has not convinced all specialists. The newcomers’ technological advantages were insufficient and in any case only temporary; differential mortality was a long-term process, not something that happened at the moment of outsiders’ assault. Thinking about the endemic vulnerabilities of empires helps us understand the situation. The Aztecs and the Incas were themselves imperial formations of relatively recent origin, with highly concentrated power and wealth at the center and often violent relations with not entirely assimilated people at the edges of their empires. When the Europeans arrived, indigenous people were not sure whether the newcomers were enemies, gods, or evil spirits–or potentially useful allies against an oppressive power. These uncertainties made it harder for their rulers, who had no way of knowing what was in store for them, to respond effectively. Cortes and Pizarro recruited allies among disaffected peoples, thereby making their armies as large as the Aztec and Inca forces they fought against. The battle against the Aztecs was hard-fought, with Spaniards suffering reverses, despite their indigenous allies and the hesitations of the Aztec emperor Moctezuma. The conquest of the Inca empire–more centralized than that of the Aztecs–was also facilitated by turning those excluded under Inca power into indigenous allies.