In Guns, Germs, and Steel, Jared Diamond describes it as an accident of history and geography that the Spanish soldiers who came to Peru with Pizarro were equipped with guns while the Inca people were not. At the beginning of the sixteenth century, various types of guns had already been developed in Asia and Europe over hundreds of years. The technology to make guns, along with gunpowder itself, probably arrived in Europe from Asia in the thirteenth century, and guns were refined for use in wars within and around Europe over hundreds of years, slowly becoming deadlier and easier to use.

Whereas the Spanish were surrounded by other European powers, also using guns and vying for power, the Incas were culturally isolated, without either the technology or the need to develop such powerful weapons. They had bronze weapons which used spears and darts as projectiles, and these were sufficient for hunting and for minor domestic conflicts but were largely useless against even the most primitive guns. These historical and geographical factors mean that the Incas, like the Aztecs and other cultures in the Americas, had no means, motive, or opportunity to develop guns and were easily overwhelmed by small bands of Europeans who did have this technology.