Warfare

«The importance of lethal microbes in human history is well illustrated by Europeans’ conquest and depopulation of the New World. Far more Native Americans died in bed from Eurasian germs than on the battlefield from European guns and swords. (…) For instance, in 1519 Cortés landed on the coast of Mexico with 600 Spaniards, to conquer the fiercely militaristic Aztec Empire with a population of many millions. (…) What gave the Spaniards a decisive advantage was smallpox, which reached Mexico in 1520 with one infected slave arriving from Spanish Cuba. The resulting epidemic proceeded to kill nearly half of the Aztecs, including Emperor Cuitláhuac. Aztec survivors were demoralized by the misterious illness that killed Indians and spared Spaniards, as if advertising the Spaniards’ invencibility. By 1618, Mexico’s initial population of about 20 million had plummeted to about 1.6 million.»

Guns, germs and steel, Jared Diamond