Disease, not conquest, was the real weapon of colonization

Mann's central claim is that European diseases — smallpox, influenza, measles, and others to which Native Americans had no prior immunity — raced ahead of European explorers and armies, killing the vast majority of the hemisphere's population often before colonizers ever arrived in a given region. He estimates that in many areas, 90 to 95 percent of the population may have died within decades of first contact, a mortality rate with few parallels in human history.

This reframes famous conquests: Hernán Cortés's defeat of the Aztec empire and Francisco Pizarro's defeat of the Inca empire succeeded partly because both empires were already reeling from epidemic disease and internal political fracture caused by the deaths of rulers and elites, not because a few hundred Europeans simply outfought millions of people through superior tactics or weaponry alone.

Mann's point isn't that conquest was bloodless or that European violence didn't matter — it plainly did — but that biology did far more of the work than the conquistadors' own triumphant accounts admitted.

Takeaway: the most devastating weapon in the conquest of the Americas wasn't steel or gunpowder — it was a microbe nobody could see coming.