The Inca Empire was the empire, its capital in the city of Cusco, that controlled much of modern-day Peru, Ecuador, northern Chile, western Bolivia, northwestern Argentina and the southern tip of Colombia between 1438–1533. Its official language was Quechua (known as Runa simi, “people’s language”, then and still in Quechua to this day), even though the Incas’ own ethnic language, the Qhapaq simi, was something different (probably a Puquina language).
The Inca Empire’s economy has been described in contradictory ways; for the Latin American socialists of the early 20th century, it was an inspirational example of indigenous socialism, but it was also an absolute monarchy that forcibly extracted labour from its subjects, so really more an example of feudalism. What they did do was establish and control an impressively thorough network of trade routes; they derived their power from their ability to use those routes to supply citizens in disparate parts of the empire with goods produced in totally separate parts of the empire. The economy was centrally planned, and run largely without money or markets; instead it was based on reciprocity between different regions, with “taxes” taken in the form of labour obligations.
In addition to their excellent road network, some of the achievements of the Incas are considered to be their architecture (especially the stone work), their finely-woven textiles, their agricultural innovations, and their quipus, knotted strings used for record-keeping. Western anthropologists marvelled that the Incas managed to achieve such a vast empire without things their European equivalents had access to, like wheels, draft animals, and a writing system.
The Inca civilisation succeeded previous Andean civilisations, which it shared a common continuity with. They began to expand from their base in Cusco in 1438, and reached their maximum extent within a few decades. Smallpox reached Inca territory and began to devastate its population in the 1520s, ahead of the arrival of Spanish colonisers in 1526 and more persistently in 1532 (they overthrew the Incan leadership in 1533). There were periodic attempts to overthrow the Spanish and re-establish Inca rule until the late 18th century.
The population of the Inca Empire at its height is not really known, even though the Incans kept excellent records in their quipus, because the knowledge of how to read them has been lost. The most common estimates are between 6–14 million.
The Incans adhered to a polytheistic religion but particularly revered Inti, their sun god, and considered their king, the Sapa Inca, the sun’s son. The Inca Empire did practise human sacrifice, particularly of children, in a ritual called qhapaq hucha in Quechua or capacocha in Spanish. They carried these out at significant moments in the Sapa Inca’s life (accesssion to the throne, birth of a male heir, illness, etc.) or to try to appease the gods during times of hardship, like famines. In Incan ideology it was an honour, rather than a punishment, to be sacrificed to the gods, and they sought to choose the “best” offerings. All parts of the empire were called on evenly to supply sacrifices, which would be boys aged about 10 or girls up to 16. They would be treated well for some period of time before the “best” among them would be picked out, taken to a place of sacrifice, drugged with alcohol and/or coca leaves, and killed (generally by a blow to the head, suffocation, strangulation, or being buried alive, but in very cold places sometimes by being left to die of exposure). The Children of Llullaillaco are one example of such sacrifices. Spanish colonial accounts of the practice don’t seem to be totally accurate, both exaggerating the number of sacrifices (there’s no evidence they’d sacrifice thousands at a time) and the method of killing (there are accounts of the heart being cut out – it’s thought the Spanish saw the Aztecs doing this and wrongly assumed the Incas did it as well).