How did Pizarro capture an Inca emperor surrounded by thousands of warriors?

Pizarro captured the Inca emperor with a trap, at a moment when the empire was already weakened. In 1532 a force of 168 Spanish soldiers under Francisco Pizarro, with Indian auxiliaries, captured the last Sapa Inca, Atahualpa, at the Battle of Cajamarca. The wider campaign took decades and ended in Spanish victory in 1572.

The timing mattered. The Inca Empire had grown from about 400,000 square kilometres in 1448 to about 1,800,000 in 1528. But in the late 1520s the emperor Huayna Capac and his designated heir died suddenly. One account dates this to 1528 and blames what was probably smallpox, brought by the Spanish; other sources give 1527 for Huayna Capac, and some historians doubt it was smallpox at all. Either way, the succession was thrown open, and his sons Huáscar and Atahualpa fought a civil war. Pizarro invaded in the midst of it, and the news that Atahualpa's generals had finally won arrived on the same day Pizarro's band came down into Cajamarca.

Then the trap. Atahualpa was encamped with nearly 80,000 battle-tested troops and felt he had little to fear from Pizarro's tiny army. The plan was audacious: capture the emperor from within the midst of his own armies. Atahualpa came into the plaza with over seven thousand attendants, who were unarmed apart from small ceremonial axes, while the Spanish waited hidden in the buildings around the plaza. The Spanish killed thousands of his counselors, commanders and unarmed attendants, and many scholars prefer to call the event the Cajamarca massacre.

The Spanish also had help. Indigenous groups such as the Huanca, who had been under Inca control, saw a chance for revenge. Historians remain unsure whether a united empire could have beaten the Spanish.