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The Inca Empire (Quechua: Tawantinsuyu) was the largest of the pre-Columbian empires in the Americas. Its administrative, political and military center was located in Cusco, Peru.

The Incas used a form of fortification that had been perfected thousands of years earlier in the Andes: hillforts with concentric walls and narrow entrances, strategically located on passes and natural routes of travel. In the rugged Andean landscape of hills, sweeping views, and constrained routes of travel, such hillforts offered significant defensive advantages. But the Incas relied on them less than many Andean societies in the preceding centuries. Inca fortifications are rare in the heartland, perhaps because of the rapid and aggressive growth of the empire. In the earliest phase of Inca expansion, some new fortifications and encircling walls were built at recently subjugated centers in the Cuzco region: Raqchi, War’qana, Wat’a, and Pumamarca. Most sites we can confidently call Inca forts, however, are found at strategic points and passes near the edges of the empire, suggesting that investment in frontier defenses was a relatively late development. (Exceptions are northern Chile near the Atacama region, which may correspond to an earlier frontier or to an area where special vigilance was necessary, and the Calchaquí area in Argentina, where Inca forts safeguarded valuable metallic ore extraction and production.)

The distribution of Inca forts is uneven, with some frontiers much more heavily fortified than others: the northern frontier in Ecuador, the eastern rim of the highlands in Bolivia, some distance within the southeastern frontier in Argentina, and near the southern limits of Tahuantinsuyu in Chile. Forts have not been reported on the poorly studied eastern frontier in Peru. In some cases, the Incas reutilized earlier native forts after their capture; this pattern is particularly common in the southern empire. In other cases, they built new fortifications, as in Ecuador. The patchy distribution of Inca strongholds shows they were not built as a blanket policy, but as needed, to support difficult campaigns of expansion or counter threats by hostile unconquered people. For instance, cordons of forts in Ecuador’s Guayllabamba, Chilo, and Manchachi valleys correspond to documentary descriptions of the Inca offensive campaign against hostile Cayambe and Caranqui peoples late in the empire’s history.

During the period of hostilities, garrison forces were stationed at the larger forts more or less permanently. Architectural complexes at some forts would have accommodated sizable populations, who might have included not just soldiers, but their wives or families as well. For instance, evidence of weaving and textile-working at Rumicucho in Ecuador suggests that women were present. Mitmacuna (colonists from elsewhere in the empire) are routinely mentioned in the chronicles as garrison populations, placed both in frontier forts and in provinces whose loyalties were suspect. Interior garrisons in the provinces have been hard to identify archaeologically. A hilltop garrison of mitmacuna in the Lurín valley near Lima kept watch for trouble, and Inca complexes on recaptured rebel hill forts in the Titicaca basin were probably garrisoned. But many interior “garrisons” of loyal mitmacuna may not have been fortified at all; their mere presence would have discouraged sedition, and formed the first trip wire of alarm in case of rebellion.

Inca forts varied considerably in construction, size, layout, and defensibility. Construction sometimes showcased elaborate Cuzco-style masonry, but more often reflected regional traditions and conditions, perhaps making use of local labor. For example, shoot holes are found in Inca forts in the southern empire, but not in the central or northern Andes, while trenches are found in the north and not in the south.

An important functional distinction can be made between small outposts with little internal architecture, and larger, architecturally complex, permanently occupied installations. Small outposts are often found near a larger fort, supporting and extending the geographic reach of its military functions, providing extra vigilance and a base for flanking attacks. This “defense in depth” strategy is superbly illustrated at the Pambamarca hill range northeast of Quito, Ecuador, where several subsidiary watch posts bearing little sign of occupation are interspersed among larger, heavily fortified, permanently occupied forts with stockpiles of slingstones.

While some forts were highly defensive, at others, ceremonial and administrative priorities largely dictated site layout. Indeed, Inca forts did more than defend routes into Inca territory; they were strategically placed nodes for exchange and gift giving, where interaction with frontier populations could be managed and ritualized. Features such as ushnus and plazas, along with feasting debris, suggest that some large Inca forts served as secure embassies for ceremonial diplomacy and the dissemination of imperial goods and mores to (semi-) independent native groups, and that ceremonial sectors were often an integral part of fort function. For instance, Incallacta in Bolivia, protected by a parapeted zigzag wall with baffled entrances, offered elaborate facilities for ceremonial performance, including a huge plaza with an ushnu and one of the largest callancas in the empire.

Thus, Inca military construction was expedient and flexible, since frontiers were dynamic and variable. Often occupied for only a short time, forts were abandoned once they outlived their usefulness. Inca forts on the eastern frontier were overrun by hostile Guaraní people shortly before the Spanish arrival, then recaptured and strengthened by the Incas. Some sites securely known to have been Inca military bases, such as Incahuasi in the Cañete valley on Peru’s central coast, are not fortified at all. That is not to mention the important military functions of unfortified provincial centers in the interior, such as Huánuco Pampa.

All this suggests that categories of “fortification” and “fort” do more to serve archaeological convenience than to capture Inca realities. This is particularly evident at high-status royal and ceremonial sites in the Cuzco heartland that cannot comfortably be called “forts,” but nonetheless demonstrate a concern for barring dangerous and unwanted people. Thick walls, such as the massive perimeter at Cacha, blocked local populations from entering Inca precincts. Sites converted from old fortified outposts, like the royal estate at Tipón, retained a defensible design. New royal estates, such as Pisac, Ollantaytambo, and Machu Picchu, incorporated defensive and exclusive elements: ridgetop locations, high walls and steep terraces, condor’s-eye vantages, and tight control points. Above all, the magnificent ceremonial complex and fortress of Sacsahuaman above Cuzco was highly defensive: massive zigzag walls provided salients for flanking fire, and the bottom course of masonry blocks was too enormous to be scaled. The complex saw action in the 1536 siege of Cuzco (as did Ollantaytambo early the following year). This is not to deny the symbolic and psychological impact of Sacsahuaman, or its valence as a sacred place, aspects that must have entered into its design as much as defensive considerations. For the Incas, there was apparently no contradiction between these functions.

Further Reading

Alconini, S. “The Dynamics of Military and Cultural Frontiers on the Southeastern Edge of the Inka Empire.” In Untaming the Frontier in Anthropology, edited by B. J. Parker and L. Rodseth, 115–46. Tucson: University of Arizona Press, 2005.

Almeida Reyes, E. Estudios Arqueológicos en el Pucara de Rumicucho (II Etapa). Quito: Museos del Banco Central de Ecuador, 1999.

Arkush, E. N. Hillforts of the Ancient Andes. Gainesville: University Press of Florida, 2011.

D’Altroy, T. N. The Incas. 2nd ed. New York: John Wiley & Sons, 2014.

D’Altroy, Terence N., Verónica I. Williams, and Ana María Lorandi. “The Inkas in the Southlands.” In Variations in the Expression of Inka Power, edited by Richard L. Burger, Craig Morris, and Ramiro Matos Mendieta, 85–134. Washington, DC: Dumbarton Oaks Research, 2007.

Hyslop, John. Inka Settlement Planning. Austin: University of Texas Press, 1990.

Plaza Schuller, F. La incursión Inca en el septentrional andino ecuatoriano. Otavalo, Ecuador: Instituto Otavaleño de Antropología, 1976.

Raffino, R., and Stehberg, R. “Tawantinsuyu: The Frontiers of the Inca Empire.” In Archaeology in Latin America, edited by G. G. Politis and B. Alberti, 168–83. London: Routledge, 1999.

Forschungsmitarbeiter Mitch Williamson is a technical writer with an interest in military and naval affairs. He has published articles in Cross & Cockade International and Wartime magazines. He was research associate for the Bio-history Cross in the Sky, a book about Charles ‘Moth’ Eaton’s career, in collaboration with the flier’s son, Dr Charles S. Eaton. He also assisted in picture research for John Burton’s Fortnight of Infamy. Mitch is now publishing on the WWW various specialist websites combined with custom website design work. He enjoys working and supporting his local C3 Church. “Curate and Compile“
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