What military mistake did the incas make?

The Incas made a critical military mistake by underestimating the Spanish conquistadors, led by Francisco Pizarro, during the conquest of their empire. They failed to recognize the threat posed by the relatively small Spanish force, which utilized superior weaponry and tactics, as well as forming alliances with rival indigenous groups. Additionally, the Incas were unprepared for the impact of European diseases, which weakened their population and military capacity. This combination of overconfidence and misjudgment ultimately led to their downfall.