He began an era of conquest that, within three generations, expanded the Inca dominion from the valley of Cusco to a sizeable part of western South America.

According to the Inca chronicler Garcilaso de la Vega, Pachacuti created the Inti Raymi to celebrate the new year in the Andes of the southern hemisphere.

[16] Before the coronation, Pachacuti was referred to as Inga Yupangui, with the Spanish navigator Pedro Sarmiento de Gamboa additionally claiming Pachcuti's first name was Cusi.

[20][15] The linguists, anthropologists, archeologists, ethnologists and historians Martti Pärssinen,[13] Catherine Julien,[21] Rodolfo Cerrón Palomino,[14] Alfred Métraux,[22] Brian S. Bauer,[14] John Howland Rowe,[23] Franck Salomon,[14] Waldemar Espinoza Soriano, José Antonio del Busto Duthurburu, Gary Urton,[20] and María Rostworowski,[24] and Carmen Bernand[23] consider Pachacuti to be historical, while others, such as Pierre Duviols,[15] Juan Ossio Acuña,[25] Reiner Tom Zuidema, and Franck Garcia[15] consider Pachacuti to be mythological or mytho-historical.

According to the archeologist Franck Garcia, the story of Pachacuti's reign was mainly symbolical and served to set philosophical principles, Inca history having the structural elements of a myth.

[15] John Howland Rowe analyzed and compared various colonial sources and came to the conclusion that there existed a state-sanctioned "standard history", believing Pachacuti's victory over the Chanka people to be the cause of imperial expansion.

The Dutch structuralist anthropologist Reiner Tom Zuidema criticised Rowe and Rostworowski for methodological practices, and studied the symbolical territorial organization of Cusco and its surroundings.

[4] The Peruvian historian José Antonio del Busto Duthurburu wrote Pachacuti was born in 1403, defended Cusco from the Chankas in 1424, and reigned from 1425 to 1471.

[31] The Bolivian historian Mariano Baptista Gumucio and Santos García Ortiz found Amaru Yupanqui to have reigned independently in 1478, following Pachacuti's death, before quickly being overthrown.

Analyzing the colonial writings, the historian and anthropologist María Rostworowski concluded that, based on Andean traditions of succession, which allowed for the "most able" to take power, Pachacuti was not the son of Inca Viracocha, rendering him illegitimate in the eyes of the Spaniards, who believed in European concepts of primogeniture.

During the subsequent assault on Cusco, the Chankas were repelled, so severely that legend tells even the stones rose up to fight on Yupanqui's side.

Cusi Yupanqui captured many Chanka leaders, who he presented to his father Viracocha for him to wipe his feet on their bodies, a traditional victory ritual.

[41] For María Rostworowski, González Carré, Luis Millones and Brian Bauer, the conflict with the chankas was a "legendary saga" and part of the ancient Wari tradition.

[41][40] For Terence N. D'Altroy, while potentially containing historical elements, the saga of the chanka-inca war "may still be mostly a glorious epic invoked to burnish the image of the emperor's father", Viracocha Inca.

[citation needed] To record the history of the previous Inca rulers of Cusco, Pachacuti ordered the creation of painted wooden panels, which, in relation to oral texts, often in the form of mnemonic songs sung at important celebrations, and quipus, which contained simple and stereotyped information according to colour, order and number, decipherable by Quipucamayocs, represented official and state-sanctioned pre-imperial history.

[19] In order to "incanize" provincial elites culturally and linguistically, Pachacuti gave women from Cusco to the surrounding local chiefs to be their main wives, who's children would rule over their chiefdoms.

Instituting the system of reciprocity (a socio-economic principle regulating relations, based on obligatory and institutional mutual, "give and take", assistance) to assert his authority, Pachacuti summoned the surrounding kurakas (chiefs) to Cusco, and prepared "lavish feasts and ceremonies", tactically displaying much generosity and sharing gifts, including the booty of the war against the Chankas, before articulating gradually growing demands such as the construction of warehouses, the stocking of produce, the creation of an army, and the improvement of infrastructure.

[11][12] The first months of his reign were spent putting down revolts by surrounding chiefs in the Cusco valley and consolidating the territorial base of the polity, confronting the Ayarmacas, the Ollantaytambo, the Huacara, and the Toguaro.

[46] His first military campaign, led personally by the emperor and his general Apo Mayta, was set against the Chankas' former allies, and the chiefdoms surrounding Cusco.

As part of his vision of a statesman and warrior chieftain he conquered many ethnic groups and states, highlighting his conquest of the Collao that enhanced the prestige of the Inca Pachacuti.

Due to the remarkable expansion of their domains he was considered an exceptional leader, enlivening glorious epic stories and hymns in tribute to his achievements.

[20] Following the construction of the Qurikancha, the "temple of gold" dedicated to the sun, Pachacuti sent an army near the border with the Colla chiefdom, before joining his forces not long after.

Following the victory, Pachacuti occupied the principal city, Hatunqulla, and from there he received the submission of the Lupacas, the Pacasas and the Azangaros (previously a tributary chiefdom of the Collas).

However, in 1992, the Finnish ethno-historian Martti Pärssinen, pointing to local colonial sources, wrote that Pachacuti's generals reached the nation of Charcas, near lake Poopó.

[53][55] Pachacuti potentially also conquered parts of Kuntisuyu, where many Aymara enclaves of the highland kingdoms existed, including the regions of Arequipa, Camana and Tarapacá.

[57] According to Sarmiento de Gamboa, an army of around 200.000 men was assembled, commanded by Amaru Topa Inca, Tupac Ayar Manco and Apu Paucar Usnu, to put it down.

The Inca armies occupied the fortress of Urcocollac, advanced through territories of the central Andes, including those of the Huanca, the Yauyos and the Atavillos.

[65][66][67] Martti Pärssinen wrote that the territories north of Tomebamba and Cañar were potentially conquered after Pachacuti's reign, who abdicated in favor of his successor according to the chronicler Martín de Murúa.

[56] According to the traditions collected by colonial chroniclers, Amaru was a "gentle individual" concentrated on "agriculture and the construction of hydraulic canals".

[76] Amaru continued to have an important place in the government following his co-rule; he profited from a private estate and was in charge of the huacas (sacred sanctuaries) of the Qullasuyu region.