Germ warfare. It is the use of disease and germs to kill on a large scale. Now the reason why germ warfare was so effective against the Inca Empire was because the Incans had absolutely zero resistance to the diseases that the Spanish were used to. Because they had survived on their own and had been completely self-sufficient for so long, they had never met any outsiders before, (particularly any Europeans) and so when the Spanish brought their diseases over, the immune systems of the native Incan people were completely defenseless.
Biological warfare was effective against the Inca because there immune system's were not used to that type of diseases that Europeans brought over. There are very susceptible to disease and were wiped out quickly
