The Inca first appeared in what is today southeastern Peru during the 12th century A.D. According to some versions of their origin myths, they were created by the sun god, Inti, who sent his son Manco Capac to Earth through the middle of three caves in the village of Paccari Tampu. After killing his brothers, Manco Capac led his sisters and their followers through the wilderness before settling in the fertile valley near Cusco circa 1200.
The Inca began expanding their land holdings by the reign of their fourth emperor, Mayta Capac. However, they did not truly become an expansive power until the eighth emperor, Viracocha Inca, took control in the early 15th century. Bolstered by the military capabilities of two uncles, Viracocha Inca defeated the Ayarmaca kingdom to the south and took over the Urubamba Valley. He also established the Inca practice of leaving military garrisons to maintain peace in conquered lands.
When the rival Chancas attacked circa 1438, Viracocha Inca retreated to a military outpost while his son, Cusi Inca Yupanqui, successfully defended Cusco. Taking the title of Pachacuti, Inca Yupanqui became one of the Inca’s most influential rulers. His military campaigns extended the kingdom to the southern end of the Titicaca Basin, and hundreds of miles north to subject the Cajamarca and Chimu kingdoms.
The expanding reach of the Inca state, Tawantinsuyu, prompted strategic logistical considerations. Pachacuti Inca Yupanqui is believed to have been the first Inca emperor to order forced resettlement to squash the possibility of an uprising from one ethnic group. In addition, he established the practice in which rulers were prevented from inheriting the possessions of their predecessors, thereby ensuring that successive leaders would conquer new lands and accumulate new wealth.
Pachacuti Inca Yupanqui also focused his efforts on strengthening Cusco, the center of the empire. He expanded Sacsahuaman, the massive fortress that guarded the city, and embarked on an expansive irrigation project by channeling rivers and creating intricate agricultural terraces.
Although Tawantinsuyu was comprised of more than 100 distinct ethnic groups among its 12 million inhabitants, a well-developed societal structure kept the empire running smoothly. There was no written language, but a form of Quechua became the primary dialect, and knotted cords known as quipu were used to keep track of historical and accounting records. Most subjects were self-sufficient farmers who tended to corn, potatoes, squash, llamas, alpacas and dogs, and paid taxes through public labor. A system of roadways adding up to approximately 15,000 miles crisscrossed the kingdom, with relay runners capable of advancing messages at the rate of 150 miles per day.
The Inca religion centered on a pantheon of gods that included Inti; a creator god named Viracocha; and Apu Illapu, the rain god. Impressive shrines were built throughout the kingdom, including a massive Sun Temple in Cusco that measured more than 1,200 feet in circumference. Powerful priests depended on divination to diagnose illness, solve crimes and predict the outcomes of warfare, in many cases requiring animal sacrifice. The mummified remains of previous emperors were also treated as sacred figures and paraded around at ceremonies with their stores of gold and silver.
Upon ascending to the throne in 1471, Topa Inca Yupanqui pushed the southern border of the empire to the Maule River in modern-day Chile, and instituted a tribute system in which each province provided women to serve as temple maidens or brides for celebrated soldiers. His successor, Huayna Capac, embarked on successful northern campaigns that carried to the Ancasmayo River, the current boundary between Ecuador and Colombia.
Meanwhile, the arrival of Spanish explorers had already triggered the collapse of the state. The Spanish carried such alien diseases as smallpox, which wiped out a huge chunk of the population before killing Huayna Capac and his chosen successor around 1525. That sparked a civil war as would-be emperors battled for power, with Atahualpa eventually outlasting his half-brother, Huascar, to grab the throne.
Enamored by the stories of Inca wealth, Spanish conquistador Francisco Pizarro lured Atahualpa to meeting for a supposed dinner in his honor and kidnapped the emperor in November 1532. Atahualpa was executed the following summer, and although the Spanish were far outnumbered by the locals, they easily sacked Cusco in late 1533 with their superior weaponry.
Attempting to keep the peace, the Spanish installed a young prince named Manco Inca Yupanqui as a puppet king, a move that backfired during a spirited rebellion in 1536. However, Manco Inca Yupanqui and his men were eventually forced to retreat to the jungle village of Vilcabamba, which remained the last stronghold of the empire until 1572.
As the only written accounts of the Inca were composed by outsiders, its mythology and culture passed to successive generations by trained storytellers. Traces of its existence were mainly found in the ruins of cities and temples, but in 1911 archaeologist Hiram Bingham discovered the intact 15th century mountaintop citadel of Machu Picchu, its magnificent stone structures reflecting the power and capabilities of this massive Pre-Colombian state.