The small Spanish force could not have survived the siege of Cusco or conquered the empire alone. They relied critically on thousands of native auxiliaries from rival ethnic groups, as well as Inca nobles who opposed Emperor Manco, turning the conflict into a multi-sided civil war.

Despite commanding armies of tens of thousands, Inca generals were so disoriented by the unheard-of capture of their divine emperor that they offered no resistance. This complete bewilderment allowed a handful of Spaniards to dictate terms to a vastly superior force.

Focused on winning his civil war, Atahualpa fatally misjudged the Spanish. He saw the small group as a potential asset—a source of mercenaries, horses, and superior swords to be captured and repurposed. He never considered them an existential threat to his empire, which sealed his fate.

The Spanish didn't defeat the Inca Empire at its height. They arrived after a smallpox epidemic killed the emperor and a subsequent brutal civil war between his sons shattered the empire. This left the civilization politically fractured and militarily exhausted, making it ripe for conquest by a small force.

The absolute divine authority of the Sapa Inca meant that capturing a single man, Atahualpa, effectively paralyzed a 12-million-person empire. With no alternative power structure, his generals were bewildered and leaderless, allowing a tiny Spanish force to maintain control.

Manco first viewed the small Spanish force as mercenaries he could leverage to restore order and his own authority after the devastating Inca civil war, completely underestimating their ultimate colonial ambitions and disruptive potential.

The Aztecs' and Incas' centralized, hierarchical structure was their greatest vulnerability. By capturing a single leader—the emperor—the Spanish could destabilize or control the entire system. In contrast, dispersed peoples like the Maya required a long, grinding war of attrition to subdue.

The narrative of a small Spanish force conquering a vast empire is misleading. The Spanish heavily relied on indigenous allies, like the puppet emperor Paolo Inca, who provided thousands of warriors. These alliances were decisive in key battles, revealing the conquest was also a native civil war exploited by Europeans.

The Spanish conquest of the Incas succeeded largely because they inserted themselves into an existing civil war. By siding with the southern Inca faction against the northern one, they gained crucial local allies, transforming the conflict from a foreign invasion into a complex, multi-sided war they could manipulate.