Why the Spanish Were Able to Conquer the Inca Empire

The conquest of the Inca Empire by a small Spanish force between 1532 and 1572 is one of the most cited cases in the literature on European overseas expansion, and the question of how a few hundred Spanish soldiers were able to overthrow a state of perhaps ten million people has been the subject of an extensive historical literature. The conventional explanations — the military superiority of the Spanish, the political disunity of the Andean peoples, and the catastrophic impact of European epidemic disease — are all relevant, but none is by itself sufficient. The most accurate answer is that the conquest succeeded because of a rare conjunction of military technology, epidemiological catastrophe, political fragmentation, and the deliberate collaboration of large numbers of indigenous auxiliaries who saw the Inca state as a relatively recent imperial imposition. Each of these factors amplified the others, and it is the combination, rather than any single cause, that explains the speed and the finality of the Spanish victory.

Military factors

Steel, horses, and firearms

The Spanish forces that invaded Peru in 1531–1532 were equipped with three military technologies that had no equivalent in the Andes: steel swords, plate armor, and the horse. The Andean military tradition was based on the use of wooden clubs, maces, slings, and spears tipped with copper or with bone, none of which was effective against steel plate. The Spanish sword, in particular the espada de dos manos and the lighter rodelero sword, gave the Spanish infantry a decisive advantage in hand-to-hand combat, and the Spanish steel helmet and breastplate protected the wearer from the worst of the indigenous missile weapons. The arquebus, a heavy matchlock firearm, was effective at a range of perhaps fifty meters, but it was slow to load and was less important in the early campaigns than the steel sword.

The horse was the most important single military advantage. The Andean peoples had never seen a horse, and the animal’s size and speed had a devastating psychological effect in the early encounters. The Spanish cavalry, of which there were perhaps 62 in the third Pizarro expedition, fought as a shock weapon, charging in formation and using the lance or the sword. In open country, the Spanish cavalry could disperse a much larger indigenous force; in confined spaces, such as the main square of Cajamarca, the effect was even more decisive. The Andean armies, which had no tradition of cavalry warfare, were unable to develop an effective counter-tactic against the Spanish horse in the early campaigns, and it was not until the indigenous rebellions of the 1530s and 1560s that the Andean forces began to use the highland terrain to neutralize the Spanish advantage.

Tactics and leadership

The Spanish forces were also tactically flexible and well led. The Spanish captains — Francisco Pizarro, Diego de Almagro, Hernando Pizarro, Sebastián de Benalcázar — were experienced soldiers who had fought in the Italian Wars and in the conquest of the Caribbean, and they applied the small-unit tactics and the combined-arms doctrine that they had learned in Europe to the Andean context. The Spanish used the highland road system — the Qhapaq Ñan — to move their forces quickly across the empire, and they took possession of the imperial storehouses along the road to provision their armies. The Inca, by contrast, were slow to adapt to the new style of warfare, and their commanders, who had been trained in the traditional Inca manner of set-piece battles on open ground, were unable to cope with the Spanish hit-and-run tactics.

Political and epidemiological factors

The civil war of succession

The Spanish arrived in 1532 in the middle of a civil war of succession between the half-brothers Huáscar and Atahualpa. The war, which had begun in 1529 after the death of the Sapa Inca Huayna Capac from smallpox, had ended in 1532 with the defeat of Huáscar at the battle of Quipaipán and the installation of Atahualpa as Sapa Inca. The civil war had been extremely destructive. Both armies had used scorched-earth tactics in the populated valleys, and the highland population, already weakened by smallpox, had been further reduced by famine and displacement. The empire was divided, the capital had been sacked, and the population of the central and southern highlands had suffered significant losses.

The Spanish were able to exploit the disequilibrium of the civil war in several ways. They were able to make alliances with the Cañari of southern Ecuador and the Chachapoya of the cloud forest, both of whom had been incorporated into the Inca empire only recently and resentfully. They were able to use the news of the epidemic of smallpox to frighten the Andean population, and they were able to present themselves as a third force in the civil war, willing to support either side. The capture of Atahualpa at Cajamarca in November 1532 left the political authority of the northern state without a leader, and the installation of a younger son of Huayna Capac, Manco Inca Yupanqui, as a puppet Sapa Inca divided the Inca nobility and made a unified resistance to the Spanish impossible.

The role of epidemic disease

The single most important factor in the Spanish victory was the catastrophic impact of European epidemic disease on the Andean population. The first epidemic of smallpox reached the Andes from the Caribbean coast in 1524 and spread along the Qhapaq Ñan through the northern highlands. The epidemic killed the Sapa Inca Huayna Capac and his designated heir, Ninan Cuyochi, and it set off the civil war of succession that weakened the empire on the eve of the Spanish arrival. The second epidemic, also of smallpox, reached Peru in 1529 or 1530, and a third, of measles, arrived in 1531 or 1532. Over the course of the sixteenth century, a series of further epidemics — of influenza, measles, typhus, and diphtheria — followed, with a cumulative mortality that the historian Noble David Cook has estimated at about 86 percent of the central Andean population between 1520 and 1620.

The impact of disease on the conquest was threefold. First, the epidemics weakened the Andean population directly, reducing the labor force available for the Inca armies and the Inca state. Second, the epidemics destabilized the Inca political system, killing the Sapa Inca and his designated heir and setting off a succession dispute that the Spanish were able to exploit. Third, the epidemics created a climate of religious anxiety in the Andes, in which the traditional religious authorities were unable to explain the new diseases, and in which the Spanish were able to present themselves as having a special relationship with the Christian God who, the Andean peoples feared, had sent the diseases.

Indigenous allies and the structure of the empire

The role of indigenous auxiliaries

The Spanish did not conquer Peru alone. From the first expedition of 1531–1532, the Spanish forces were accompanied by large numbers of indigenous auxiliaries, drawn from groups that had been incorporated into the Inca Empire only recently and resentfully. The most important of these were the Cañari of southern Ecuador, the Chachapoya of the cloud forest, and the Huancas of the central highlands. The Cañari, in particular, had fought against the Inca in the civil war and had been punished by Atahualpa for their support of Huáscar; the Spanish were able to recruit thousands of Cañari warriors by promising them an end to Inca rule. The Chachapoya, who had been resettled in the north by the Inca, were also willing allies, and the Huancas, who had been the victims of a major Inca military campaign in the 1460s, joined the Spanish against the Inca. By the time of the conquest of Cusco in 1533, the Spanish force included perhaps as many as 30,000 to 40,000 indigenous auxiliaries, without whom the conquest would not have been possible.

The structure of the Inca state

The Inca state, although it was the largest in the pre-Columbian Americas, was structurally vulnerable to the kind of attack the Spanish mounted. The state was administered through a system of labor extraction — the mit’a — and a system of forced resettlement — the mitma — that imposed significant costs on the subject populations. The state had been built up over the course of a century, and many of the peoples incorporated into it had been subjects of the Inca for only a generation or two. The political authority of the Sapa Inca depended on a combination of religious legitimacy, military power, and the redistribution of resources through the state storehouses, and when the Sapa Inca was killed or captured, the system was unable to function.

The state was also vulnerable because of the absence of a formal written language. The Inca used the quipu, a system of knotted cords, for accounting and for the transmission of information, but the quipu was not a writing system in the European sense, and the Spanish were able to intercept the quipu-based communications of the Inca with relative ease. The state was also vulnerable because of the concentration of political authority in the Sapa Inca: the death or capture of the Sapa Inca left the state without a legitimate ruler, and the civil war of succession showed that there was no agreed mechanism for the transfer of power.

The cumulative effect

The Spanish conquest of the Inca Empire was, in short, the product of a rare conjunction of factors that, taken together, made the conquest possible and even, in some sense, inevitable. The military technology of the Spanish — steel, horses, and firearms — gave them a decisive advantage in open battle. The epidemiological catastrophe of European disease weakened the Andean population and destabilized the Inca political system. The civil war of succession between Huáscar and Atahualpa divided the empire at the moment of the Spanish arrival. The collaboration of large numbers of indigenous auxiliaries gave the Spanish forces a numerical superiority that their own recruits could not have provided. The structural vulnerability of the Inca state made it unable to mount a sustained resistance to the Spanish once the Sapa Inca had been captured. None of these factors would have been sufficient by itself, and the conquest is best understood as a contingent event whose outcome depended on the specific conjunction of all of them in the years between 1525 and 1532.