In Guns, Germs, and Steel, Jared Diamond says that there are both proximate causes and ultimate causes of European domination of the world. In Chapter 3, he introduces us to the proximate causes. These are the causes that led directly to Europeans being able to dominate other peoples of the world. Diamond uses the story of the capture of Atahualpa to illustrate those proximate causes. The proximate causes are summarized in one sentence at the bottom of page 80. There, Diamond says that
Immediate reasons for Pizarro's success included military technology based on guns, steel weapons, and horses; infectious diseases endemic in Eurasia; European maritime technology; the centralized political organization of European states; and writing.
Diamond says that these are the factors that made it so that the Spanish sailed to South America and conquered the Incas instead of the Incas sailing to Europe and conquering Spain. He takes these factors and reduces them to the three factors, “guns, germs, and steel” that make up the title of the book.
But this is really just the setup for the book as a whole. Diamond is not particularly interested in the proximate causes of European domination because those causes are easily seen. It is easy to say that the Spanish defeated the Incas because they had germs and superior technology. To Diamond, the much more important question is why the Spanish had these things and the Incas did not. That is, for Diamond, the real focus of this book.
Pizarro’s capture of Atahualpa helps Diamond to get his point across because it explains why the Spanish were able to conquer the Incas. It shows how and why the “guns, germs, and steel” helped the Spanish conquer the Incas and not vice versa.