What were the primary reasons for their defeat? Do you think that their defeats were inevitable? Why or why not?

Both the Inca Empires and Inca Empires fell in the early sixteenth century when confronted with Spanish forces of a few hundred men.

What were the primary reasons for their defeat? Do you think that their defeats were inevitable? Why or why not?
Please use 5 reliable sources and list them at the end of your research paper.