The Battle of Cajamarca was a surprise attack on the Inca royal entourage orchestrated by Francisco Pizarro. Sprung in the evening of November 16, 1532 in the great plaza of Cajamarca, the ambush, lasting no more than half an hour, achieved its singular goal of capturing Emperor Atahualpa.
The confrontation at Cajamarca was the culmination of a months-long contest of espionage, subterfuge, and diplomacy conducted by Pizarro and the Inca via their respective envoys. Atahualpa had received the invaders from a position of immense strength. Encamped along the heights of Cajamarca with legions of battle-tested troops fresh from their victories in the civil war against his half-brother Huascar, the Inca had little to fear from Pizarro's minute army, however extravagant its dress and weaponry. In a calculated show of goodwill, he had lured the adventurers deep into the heart of his mountain empire where any potential threat could be met with a show of force. The Spaniards arrived on November 15. Atahualpa, according to Spanish sources, planned to recruit a few of the conquistadores into his own service and to appropriate Spanish firearms and horses for his armies.
According to a book called History Of The Conquest Of Peru, written by 19th century author William H. Prescott, he recounts the Spanish invasion in the city plaza, any assault on the Inca armies overlooking the valley would have rightly seemed suicidal. Retreat was equally out of the question, because any gesture of weakness that might undermine their inflated display of potency would invite furious pursuit and the sealing of the mountain passes. Once the great stone fortresses dotting their route of escape were garrisoned, argued Pizarro, they would prove impenetrable. But to do nothing, he added, to dally in the fragile and fleeting safety of the Inca's good graces, was no better, since prolonged contact with the natives would erode the fears of Spanish supernaturality that kept them at bay.
Pizarro gathered his officers on the evening of November 15 and outlined a scheme that, in its audacity, recalled memories of Hernán Cortés' exploits in Mexico: he would capture the emperor from within the midst of his own armies. Since this could not realistically be accomplished in an open field, Pizarro invited the Inca to Cajamarca.
Atahualpa accepted this invitation, but, leading a procession of over eighty thousand men, advanced down the hillside only slowly the next day. Pizarro's fortunes changed dramatically in late afternoon when Atahualpa announced that the greater part of his host would set up camp outside the walls of the city. He requested that accommodations be provided only for himself and his retinue, which would forsake its weapons in a sign of amity and absolute confidence.
Having concealed themselves within the city, the Spaniards allowed the Incas to enter unopposed. An incident occurred when friar Vincente de Valverde approached the Inca and ordered him to renounce his pagan religion and to accept Catholicism as faith and Charles V, the Holy Roman Emperor as sovereign. Atahualpa was equally insulted and confused by the Spaniard's demands. Although Atahualpa likely had no intention of conceding to their demands, according to chronicler Garcilaso de la Vega he did attempt inquiry into the Spanish faith and their king, but Pizarro's men began to grow impatient.
At once, the Spaniards unleashed murderous gunfire at the vulnerable mass of Incas and surged forward in a concerted action. The effect was devastating: the shocked and largely unarmed Incas offered such feeble resistance that the battle has often been labeled a massacre. Contemporary accounts by members of Pizzaro's force explain how the Spanish forces used a cavalry charge against the Inca forces, who had never seen horses, in combination with gunfire from cover (the Inca forces also never having encountered guns before). Other factors in the Spaniard's favour were their steel swords, helmets and armour, against the Inca forces who had only leather armour and stone or wooden clubs and spears. In addition, the first target of the Spanish attack consisted of the Inca Emperor and all of the top commanders of the army; once these had been killed or captured the Inca forces were disorganised as the command structure of the army had been effectively decapitated.
At length, Pizarro captured and imprisoned the Inca at the so-called "Ransom Room", ending all attempts at resistance. Although years of fighting would continue as the Spaniards consolidated their conquests, the Inca Empire effectively fell with a single blow at Cajamarca.