The Spanish conquest of the Inca Empire is one of the most important campaigns in the Spanish colonization of the Americas.

After years of preliminary exploration and military skirmishes, one hundred and sixty-eight Spanish soldiers under Francisco Pizarro and their native allies capture the Sapa Inca Atahualpa in the 1532 Battle of Cajamarca.

It is the first step in a long campaign that takes decades of fighting but ends in Spanish victory in 1572 and colonization of the region as the Viceroyalty of Peru.

The conquest of the Inca Empire leads to spin-off campaigns into present-day Chile and Colombia, as well as expeditions towards the Amazon Basin.When the Spanish arrive at the borders of the Inca Empire in 1528, it spans a considerable distance.

Extending southward from the Ancs Maya, which is now known as the Patía River, in southern Colombia to the Maule River in Chile, and eastward from the Pacific Ocean to the edge of the Amazonian jungles, the empire covers some of the most mountainous terrain on earth.

In less than a century, the Inca have expanded their empire from about 155,000 square miles or 400,000 square kilometers in 1448, to 690,000 square miles or 1,800,000 square kilometers in 1528, just before the arrival of the Spaniards.

This vast area of land varies greatly in cultures and in climate.

Because of the diverse cultures and geography, the Inca allows many areas of the empire to be governed under the control of local leaders, who are watched and monitored by Inca officials.

However, under the administrative mechanisms established by the Inca, all parts of the empire answer to, and are ultimately under the direct control of, the Emperor.

Scholars estimate that the population of the Inca Empire numbered more than 16,000,000.Some scholars, such as Jared Diamond, believe that while the Spanish conquest was undoubtedly the proximate cause of the collapse of the Inca Empire, it may very well have been past its peak and already in the process of decline.

In 1528, Emperor Huayna Capac ruled the Inca Empire.

He could trace his lineage back to a "stranger king" named Manco Cápac, the mythical founder of the Inca clan, who according to tradition emerged from a cave in a region called Pacariqtambo.Huayna Capac was the son of the previous ruler, Túpac Inca, and the grandson of Pachacuti, the emperor who had begun the dramatic expansion by conquest of the Inca Empire from its base in the area around Cuzco.

On his accession to the throne, Huayna Capac had continued the policy of expansion by conquest, taking Inca armies north into what is today Ecuador.

[ While he had to put down a number of rebellions during his reign, by the time of his death, his legitimacy was as unquestioned as was the primacy of Inca power.Expansion had resulted in its own problems, however.

Many parts of the empire maintain distinctive cultures and these are at best restive participants in the imperial project.

The large extent of the empire, the extremely difficult terrain of much of it, and the fact that all communication and travel haa to take place on foot or by boat, seems to have caused increasing difficulty in the Incas' effective administration of the empire.Huayna Capac relied on his sons to support his reign.

While he had many legitimate and illegitimate children (legitimate meaning born of his sister-wife, under the Inca system), two sons are historically important.

Prince Túpac Cusi Hualpa, also known as Huáscar, was the son of Coya Mama Rahua Occllo of the royal line.

The second was Atahualpa, an illegitimate son who was likely born of a daughter of the last independent King of Quitu, one of the states conquered by Huayna Capac during the expansion of the Inca Empire.

These two sons will play pivotal roles in the final years of the Inca Empire.The Spanish conquistador Pizarro and his men are greatly aided in their enterprise by invading when the Inca Empire is in the midst of a war of succession between the princes Huáscar and Atahualpa.

Atahualpa seems to have spent more time with Huayna Capac during the years when he was in the north with the army conquering Ecuador.

Atahualpa is thus closer to, and has better relations with the army and its leading generals.

When both Huayna Capac and his eldest son and designated heir, Ninan Cuyochic, died suddenly in 1528 from what was probably smallpox, a disease introduced by the Spaniards into the Americas as they conquered Mexico, the question of who would succeed as emperor was thrown open.

Huayna had died before he could nominate the new heir.At the time of Huayna Capac's death, Huáscar was in the capital Cuzco, while Atahualpa was in Quitu with the main body of the Inca army.

Huáscar had himself proclaimed Sapa Inca (i.e.

"Only Emperor") in Cuzco, but the army declared its loyalty to Atahualpa.

The resulting dispute led to the Inca Civil War.In the following years the conquistadors will manage to consolidate their power over the whole Andean region, repressing successive indigenous rebellions until the establishment of the Viceroyalty of Perú in 1542 and the fall of the resistance of Vilcabamba in 1572.