During the siege of Cusco, the Incas developed a new tactic: heating stones in campfires before wrapping them in cotton and launching them with slings. This simple innovation transformed their traditional projectile weapons into highly effective incendiary devices, setting the city's thatched roofs on fire.

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.

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 Spanish horses were a decisive factor not just for their combat effectiveness but for their psychological impact. Against Inca warriors who lacked pikes or numerous bows and arrows, a handful of cavalry seemed invincible, creating a reputation that demoralized armies thousands of times their size.

Despite their aggressive plan, the psychological toll on the 168 Spaniards facing an army of thousands was immense. A firsthand account reveals their sheer terror, noting that many "urinate without noticing it out of pure terror" while waiting in hiding for the ambush to begin.

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.

The famous moment where Atahualpa supposedly threw down a prayer book, sparking the massacre, was a manufactured pretext. The Spanish, already in ambush positions, simply needed a justification. The book ending up in the dust—whether thrown or dropped—provided the trigger for their pre-planned attack.

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.