G. A. Henty 
By Right of Conquest 

The conquest of Mexico, an extensive empire with a numerous and warlike population, by a mere handful of Spaniards, is one of the romances of history. Indeed, a writer of fiction would scarcely have dared to invent so improbable a story. Even the bravery of the Spaniards, and the advantage of superior arms would not have sufficed to give them the victory, had it not been that Mexico was ripe for disruption. The Aztecs, instead of conciliating by wise and gentle government the peoples they had conquered, treated them with such despotic harshness that they were ready to ally themselves with the invaders, and to join with them heartily against the central power; so that instead of battling against an empire single-handed, the Spaniards had really only to war with a great city, and were assisted by a vast army of auxiliaries…